U.S. patent application number 10/676711 was filed with the patent office on 2005-03-31 for personalization of web search.
Invention is credited to Lawrence, Stephen R..
Application Number | 20050071328 10/676711 |
Document ID | / |
Family ID | 34377443 |
Filed Date | 2005-03-31 |
United States Patent
Application |
20050071328 |
Kind Code |
A1 |
Lawrence, Stephen R. |
March 31, 2005 |
Personalization of web search
Abstract
A system and method for creating a user profile and for using
the user profile to order search results returned by a search
engine. The user profile is based on search queries submitted by a
user, the user's specific interaction with the documents identified
by the search engine and personal information provided by the user.
Generic scores associated with the search results are modulated by
the user profile to measure their relevance to a user's preference
and interest. The search results are re-ordered accordingly so that
the most relevant results appear on the top of the list. User
profiles can be created and/or stored on the client side or server
side of a client-server network environment.
Inventors: |
Lawrence, Stephen R.;
(Mountain View, CA) |
Correspondence
Address: |
MORGAN, LEWIS & BOCKIUS, LLP.
2 PALO ALTO SQUARE
3000 EL CAMINO REAL
PALO ALTO
CA
94306
US
|
Family ID: |
34377443 |
Appl. No.: |
10/676711 |
Filed: |
September 30, 2003 |
Current U.S.
Class: |
1/1 ;
707/999.003; 707/E17.109 |
Current CPC
Class: |
G06F 16/95 20190101;
G06F 16/93 20190101; G06F 16/248 20190101; G06F 16/24578 20190101;
G06F 16/9535 20190101 |
Class at
Publication: |
707/003 |
International
Class: |
G06F 017/30 |
Claims
What is claimed is:
1. A method of personalizing search results of a search engine,
comprising: accessing a user profile for a user based on
information about the user, the user information including
information derived from a set of documents, the set of documents
comprising a plurality of documents selected from the set
consisting of documents identified by search results from the
search engine, documents accessed by the user, documents linked to
the documents identified by search results from the search engine,
and documents linked to the documents accessed by the user;
receiving a search query from the user; identifying a set of search
result documents that match the search query; assigning a generic
score to each of at least a plurality of the search result
documents; assigning a personalized score to each document of the
plurality of search result documents in accordance with the generic
score assigned to the document and the user profile; and ranking
the set of search result documents according to their personalized
scores.
2. The method of claim 1, wherein the set of documents include a
plurality of documents that have been identified by search results
from the search engine and that have been viewed by the user.
3. The method of claim 1, wherein the set of documents include a
plurality of documents that have been identified by search results
from the search engine and that have not been viewed by the
user.
4. The method of claim 1, including updating the user profile by:
updating a term-based profile by identifying a set of terms from a
document in the set of documents, and adding information about the
identified set of terms to the term-based profile; and updating a
category-based profile by classifying the document into a plurality
of categories, and adding information about the plurality of
categories to the category-based profile.
5. The method of claim 4, including updating the user profile by:
updating a link-based profile by analyzing links in the document,
and adding information derived from the analyzed links to the
link-based profile.
6. The method of claim 5, wherein the link-based profile includes
information about URLs or portions of URLs.
7. The method of claim 6, wherein the link-based profile comprises:
a plurality of URLs and a weight associated with each URL, wherein
the weight is based on one or more factors selected from the group
consisting of frequency with which the user visits the URL, time
the user has spent viewing a document associated with the URL and
quantity of the user's scrolling activity at the document; and a
plurality of hosts and a weight associated with each host, wherein
the weight is based on frequency of the user's visits to the
host.
8. The method of claim 7, wherein the URLs further include URLs
that have not been visited by the user, but are related to the URLs
that have been visited by the user and the weight of an unvisited
URL depends on its distance to at least one related URLs that have
been visited.
9. The method of claim 4, wherein a term in the term-based profile
is an expression comprising at least one word and a weight.
10. The method of claim 9, wherein the weight is a weight
associated with occurrences of the term in the set of
documents.
11. The method of claim 9, wherein the weight of a term depends at
least partially on the term's term frequency and inverse document
frequency in said set of documents.
12. The method of claim 4, wherein a category in the category-based
profile characterizes at least one aspect of documents in the
category and the category is associated with a weight indicative of
the category's importance relative to other categories.
13. The method of claim 12, wherein the at least one aspect of the
documents in the category is selected from the group consisting of:
document format, document type, document topic and document
origin.
14. The method of claim 1, including updating the user profile by:
updating a category-based profile by classifying a document in the
set of documents into a plurality of categories, and adding
information about the plurality of categories to the category-based
profile.
15. The method of claim 1, wherein the user profile is stored on a
server of the search engine.
16. The method of claim 1, wherein the user profile is stored on a
client associated with the user.
17. The method of claim 1, wherein the user is a group of
users.
18. A method of personalizing search results of a search engine,
comprising: creating a plurality of user profiles for a plurality
of users, each user profile including at least a user's
identification number and information derived from documents
visited by the user; receiving a search query from a user of the
plurality of users, the search query including at least one query
term and the user's identification number; selecting a set of
documents from the Internet, assigning to each document in the set
a generic score that characterizes the relevance of the document to
the at least one query term; retrieving the user's user profile and
assigning to each of the set of documents a profile score based on
the user profile; and ranking the set of documents according to
their generic and profile scores.
19. The method of claim 18, wherein the step of creating a user's
user profile further comprises: creating a term-based profile by
extracting a set of terms from documents visited by the user and
associating a weight with each extracted term; and creating a
category-based profile by determining a plurality of categories
associated with documents visited by the user and associating a
weight with each determined category.
20. The method of claim 18, wherein the step of creating a user's
user profile further comprises: creating a link-based profile by
analyzing links in documents visited by the user and associating
weights with the link.
21. The method of claim 18, wherein the user profile for a
particular user includes demographic and geographic information
provided by the user.
22. The method of claim 18, wherein the documents visited by the
user from which information is derived for use in a particular
user's user profile are selected based on the user's activities
when visiting the documents.
23. The method of claim 18, including storing the plurality of user
profiles on a server of the search engine; and the retrieving
including identifying the user's user profile based on a user
identification number associated with both the user and the user's
user profile.
24. The method of claim 18, including storing the plurality of user
profiles on client computers associated with the plurality of
users.
25. The method of claim 18, wherein the ranked set of documents
comprises two sets of documents, one set of documents ordered by
their generic scores and the other set of documents ordered by
personalized scored generated by combining the document's generic
and profile scores.
26. The method of claim 25, including interleaving or intermixing
the two sets of documents to form the ranked set of documents.
27. A search engine system, comprising: one or more central
processing units for executing programs; an interface for receiving
event messages; and a search engine module executable by the one or
more central processing units, the module comprising: instructions
for accessing a user profile for a user, the user profile based on
information about the user, the user information including
information derived from a set of documents, the set of documents
comprising a plurality of documents selected from the set
consisting of documents identified by search results from the
search engine system, documents accessed by the user, documents
linked to the documents identified by search results from the
search engine system, and documents linked to the documents
accessed by the user; instructions for receiving a search query
from the user; instructions for identifying a set of search result
documents that match the search query; instructions for assigning a
generic score to each of at least a plurality of the search result
documents; instructions for assigning a personalized score to each
document of the plurality of search result documents in accordance
with the generic score assigned to the document and the user
profile; and instructions for ranking at least the plurality of the
search result documents according to their personalized scores.
28. The system of claim 27, wherein the set of documents include a
plurality of documents that have been identified by search results
from the search engine and that have been viewed by the user.
29. The system of claim 27, wherein the set of documents include a
plurality of documents that have been identified by search results
from the search engine and that have not been viewed by the
user.
30. The system of claim 27, further including: instructions for
updating a term-based profile by identifying a set of terms from a
document in the set of documents, and adding information about the
identified set of terms to the term-based profile; and instructions
for updating a category-based profile by classifying the document
into a plurality of categories, and adding information about the
plurality of categories to the category-based profile.
31. The system of claim 30, further including: instructions for
updating a link-based profile by analyzing links in the document,
and adding information derived from the analyzed links to the
link-based profile.
32. The system of claim 31, wherein the link-based profile includes
information about URLs or portions of URLs.
33. The system of claim 32, wherein the link-based profile
comprises: a plurality of URLs and a weight associated with each
URL, wherein the weight is based on one or more factors selected
from the group consisting of frequency with which the user visits
the URL, time the user has spent viewing a document associated with
the URL and quantity of the user's scrolling activity at the
document; and a plurality of hosts and a weight associated with
each host, wherein the weight is based on frequency of the user's
visits to the host.
34. The system of claim 33, wherein the URLs further include URLs
that have not been visited by the user, but are related to the URLs
that have been visited by the user and the weight of an unvisited
URL depends on its distance to at least one related URLs that have
been visited.
35. The system of claim 30, wherein a term in the term-based
profile is an expression comprising at least one word and a
weight.
36. The system of claim 35, wherein the weight is a weight
associated with occurrences of the term in the set of
documents.
37. The system of claim 35, wherein the weight of a term depends at
least partially on the term's term frequency and inverse document
frequency in said set of documents.
38. The system of claim 30, wherein a category in the
category-based profile characterizes at least one aspect of
documents in the category and the category is associated with a
weight indicative of the category's importance relative to other
categories.
39. The system of claim 38, wherein the at least one aspect of the
documents in the category is selected from the group consisting of:
document format, document type, document topic and document
origin.
40. The system of claim 27, wherein the user profile is stored on a
server of the search engine.
41. The system of claim 27, wherein the user profile is stored on a
client associated with the user.
42. The system of claim 27, wherein the user is a group of
users.
43. A computer program product for use in conjunction with a
computer system, the computer program product comprising a computer
readable storage medium and a computer program mechanism embedded
therein, the computer program mechanism comprising: instructions
for accessing a user profile for a user based on information about
the user, the user information including information derived from a
set of documents, the set of documents comprising a plurality of
documents selected from the set consisting of documents identified
by search results from a search engine, documents accessed by the
user, documents linked to the documents identified by search
results from the search engine, and documents linked to the
documents accessed by the user; instructions for receiving a search
query from the user; instructions for identifying a set of search
result documents that match the search query; instructions for
assigning a generic score to each of at least a plurality of the
search result documents; instructions for assigning a personalized
score to each document of the plurality of search result documents
in accordance with the generic scores assigned to the document and
the user profile; and instructions for ranking at least the
plurality of the search result documents according to their
personalized scores.
44. The computer program product of claim 43, wherein the set of
documents include a plurality of documents that have been
identified by search results from the search engine and that have
been viewed by the user.
45. The computer program product of claim 43, wherein the set of
documents include a plurality of documents that have been
identified by search results from the search engine and that have
not been viewed by the user.
46. The computer program product of claim 43, further including:
instructions for updating a term-based profile by identifying a set
of terms from a document in the set of documents, and adding
information about the identified set of terms to the term-based
profile; and instructions for updating a category-based profile by
classifying the document into a plurality of categories, and adding
information about the plurality of categories to the category-based
profile.
47. The computer program product of claim 46, further including:
instructions for updating a link-based profile by analyzing links
in the document, and adding information derived from the analyzed
links to the link-based profile.
48. The computer program product of claim 46, wherein the
link-based profile includes information about URLs or portions of
URLs.
49. The computer program product of claim 48, wherein the
link-based profile comprises: a plurality of URLs and a weight
associated with each URL, wherein the weight is based on one or
more factors selected from the group consisting of frequency with
which the user visits the URL, time the user has spent viewing a
document associated with the URL and quantity of the user's
scrolling activity at the document; and a plurality of hosts and a
weight associated with each host, wherein the weight is based on
frequency of the user's visits to the host.
50. The computer program product of claim 49, wherein the URLs
further include URLs that have not been visited by the user, but
are related to the URLs that have been visited by the user and the
weight of an unvisited URL depends on its distance to at least one
related URLs that have been visited.
51. The computer program product of claim 46, wherein a term in the
term-based profile is an expression comprising at least one word
and a weight.
52. The computer program product of claim 48, wherein the weight is
a weight associated with occurrences of the term in the set of
documents.
53. The computer program product of claim 48, wherein the weight of
a term depends at least partially on the term's term frequency and
inverse document frequency in said set of documents.
54. The computer program product of claim 46, wherein a category in
the category-based profile characterizes at least one aspect of
documents in the category and the category is associated with a
weight indicative of the category's importance relative to other
categories.
55. The computer program product of claim 54, wherein the at least
one aspect of the documents in the category is selected from the
group consisting of: document format, document type, document topic
and document origin.
56. The computer program product of claim 43, wherein the user
profile is stored on a server of the search engine.
57. The computer program product of claim 43, wherein the user
profile is stored on a client associated with the user.
58. The computer program product of claim 43, wherein the user is a
group of users.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to the field of a
search engine in a computer network system, in particular to system
and method of creating a user profile for a user of a search engine
and using the user profile to customize search results in response
to search queries submitted by the user.
BACKGROUND OF THE INVENTION
[0002] Search engines provide a powerful source of indexed
documents from the Internet (or an intranet) that can be rapidly
scanned in response to a search query submitted by a user. Such a
query is usually very short (on average about two to three words).
As the number of documents accessible via the Internet grows, the
number of documents that match the query may also increase.
However, not every document matching the query is equally important
from the user's perspective. As a result, a user is easily
overwhelmed by an enormous number of documents returned by a search
engine, if the engine does not order the search results based on
their relevance to the user's query.
[0003] One approach to improving the relevance of search results to
a search query is to use the link structure of different web pages
to compute global "importance" scores that can be used to influence
the ranking of search results. This is sometimes referred to as the
PageRank algorithm. A more detailed description of the PageRank
algorithm can be found in the article "The Anatomy of a Large-Scale
Hypertextual Search Engine" by S. Brin and L. Page, 7.sup.th
International World Wide Web Conference, Brisbane, Australia and
U.S. Pat. No. 6,285,999, both of which are hereby incorporated by
reference as background information.
[0004] An important assumption in the PageRank algorithm is that
there is a "random surfer" who starts his web surfing journey at a
randomly picked web page and keeps clicking on the links embedded
in the web pages, never hitting the "back" button. Eventually, when
this random surfer gets bored of the journey, he may re-start a new
journey by randomly picking another web page. The probability that
the random surfer visits (i.e., views or downloads) a web page
depends on the web page's page rank.
[0005] From an end user's perspective, a search engine using the
PageRank algorithm treats a search query the same way no matter who
submits the query, because the search engine does not ask the user
to provide any information that can uniquely identify the user. The
only factor that affects the search results is the search query
itself, e.g., how many terms are in the query and in what order.
The search results are a best fit for the interest of an abstract
user, the "random surfer", and they are not be adjusted to fit a
specific user's preferences or interests.
[0006] In reality, a user like the random surfer never exists.
Every user has his own preferences when he submits a query to a
search engine. The quality of the search results returned by the
engine has to be evaluated by its users' satisfaction. When a
user's preferences can be well defined by the query itself, or when
the user's preference is similar to the random surfer's preference
with respect to a specific query, the user is more likely to be
satisfied with the search results. However, if the user's
preference is significantly biased by some personal factors that
are not clearly reflected in a search query itself, or if the
user's preference is quite different from the random user's
preference, the search results from the same search engine may be
less useful to the user, if not useless.
[0007] As suggested above, the journey of the random surfer tends
to be random and neutral, without any obvious inclination towards a
particular direction. When a search engine returns only a handful
of search results that match a query, the order of the returned
results is less significant because the requesting user may be able
to afford the time to browse each of them to discover the items
most relevant to himself. However, with billions of web pages
connected to the Internet, a search engine often returns hundreds
or even thousands of documents that match a search query. In this
case, the ordering of the search results is very important. A user
who has a preference different from that of the random surfer may
not find what he is looking for in the first five to ten documents
listed in the search results. When that happens, the user is
usually left with two options: (1) either spending the time
required to review more of the listed documents so as to locate the
relevant documents; or (2) refining the search query so as to
reduce the number of documents that match the query. Query
refinement is often a non-trivial task, sometimes requiring more
knowledge of the subject or more expertise with search engines than
the user possesses, and sometimes requiring more time and effort
than the user is willing to expend.
[0008] For example, assume that a user submits to a search engine a
search query having only one term "blackberry". Without any other
context, on the top of a list of documents returned by a
PageRank-based search engine may be a link to www.blackberry.net,
because this web page has the highest page rank. However, if the
query requester is a person with interests in foods and cooking, it
would be more useful to order the search results so as to include
at the top of the returned results web pages with recipes or other
food related text, pictures or the like. It would be desirable to
have a search engine that is able to reorder its search results, or
to otherwise customize the search results, so as to emphasize web
pages that are most likely to be of interest to the person
submitting the search query. Further, it would be desirable for
such a system to require minimal input from individual users,
operating largely or completely without explicit input from the
user with regard to the user's preferences and interests. Finally,
it would be desirable for such a system to meet users' requirements
with respect to security and privacy.
SUMMARY
[0009] A search engine utilizes user profiles to customize search
results. A user profile comprises multiple items that characterize
a user's search preference. These items are extracted from various
information sources, including previous search queries submitted by
the user, links from or to the documents identified by the previous
queries, sampled content from the identified documents as well as
personal information implicitly or explicitly provided by the
user.
[0010] When the search engine receives a search query from a user,
it first identifies a set of documents that match the search query.
Each document is associated with a generic rank based on the
document's page rank, the text associated with the document, and
the search query. The search engine also identifies the user's
profile and correlates the user profile with each of the identified
documents. The correlation between a document and the user profile
produces a profile rank for the document, indicating the relevance
of the document to the user. The search engine then combines the
document's generic rank and profile rank into a personalized rank.
Finally, the documents are ordered according to their personalized
ranks.
[0011] In one embodiment, a user profile may comprise a plurality
of sub-profiles, each sub-profile characterizing the user's
interest from a different perspective. A term-based profile
comprises a plurality of terms, each term carrying a weight
indicative of its importance relative to other terms. A
category-based profile comprises multiple categories, optionally
organized into a hierarchical map. The user's search preferences
may be associated with at least a subset of the multiple
categories, each category having an associated weight indicating
the user's interest in the documents falling into this category.
There may be multiple category-based profiles for a user. In some
embodiments, the sub-profiles include a link-based profile, which
includes a plurality of links that are, directly or indirectly,
related to identified documents, each link having a weight
indicating the importance of the link. Links in the link-based
profile may be further organized with respect to different hosts
and domains.
[0012] The present invention, including user profile construction
and search results re-ordering and/or scoring, can be implemented
on either the client side or the server side of a client-server
network environment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The aforementioned features and advantages of the invention
as well as additional features and advantages thereof will be more
clearly understood hereinafter as a result of a detailed
description of preferred embodiments of the invention when taken in
conjunction with the drawings.
[0014] FIG. 1 illustrates a client-server network environment.
[0015] FIG. 2 illustrates multiple sources of user information and
their relationship to a user profile.
[0016] FIG. 3 is an exemplary data structure that may be used for
storing term-based profiles for a plurality of users.
[0017] FIG. 4A is an exemplary category map that may be used for
classifying a user's past search experience.
[0018] FIG. 4B is an exemplary data structure that may be used for
storing category-based profiles for a plurality of users.
[0019] FIG. 5 is an exemplary data structure that may be used for
storing link-based profiles for a plurality of users.
[0020] FIG. 6 is a flowchart illustrating paragraph sampling.
[0021] FIG. 7A is a flowchart illustrating context analysis.
[0022] FIG. 7B depicts a process of identifying important terms
using context analysis.
[0023] FIG. 8 illustrates a plurality of exemplary data structures
that may be used for storing information about documents after
term-based, category-based and/or link-based analyses,
respectively.
[0024] FIG. 9A is a flowchart illustrating a personalized web
search process according to one embodiment.
[0025] FIG. 9B is a flowchart illustrating a personalized web
search process according to another embodiment.
[0026] FIG. 10 is a block diagram of a personalized search
engine.
[0027] Like reference numerals refer to corresponding parts
throughout the several views of the drawings.
DESCRIPTION OF EMBODIMENTS
[0028] The embodiments discussed below include systems and methods
that create a user profile based a user's past experience with a
search engine and then use the user profile to rank search results
in response to search queries provided by the user.
[0029] FIG. 1 provides an overview of a typical client-server
network environment 100 in which the present invention may be
implemented. A plurality of clients 102 are connected to a search
engine system 107 through a network 105, e.g., the Internet. Search
engine system 107 comprises one or more search engines 104. A
search engine 104 is responsible for processing a search query
submitted by a client 102, generating search results in accordance
with the search query and returning the results to the client.
Search engine system 107 may also comprise one or more content
servers 106 and one or more user profile servers 108. A content
server 106 stores a large number of indexed documents retrieved
from different websites. Alternately, or in addition, the content
server 106 stores an index of documents stored on various websites.
In one embodiment, each indexed document is assigned a page rank
according to the document's link structure. The page rank serves as
a query independent measure of the document's importance. A search
engine 104 communicates with one or more content servers 106 to
select a plurality of documents in response to a specific search
query. The search engine assigns a score to each document based on
the document's page rank, the text associated with the document,
and the search query.
[0030] A user profile server 108 stores a plurality of user
profiles. Each profile includes information that uniquely
identifies a user as well as his previous search experience and
personal information, which can be used to refine search results in
response to the search queries submitted by this user. Different
approaches are available for user profile construction. For
example, a user profile can be created by requiring a first-time
user to fill in a form or answer a survey. This approach may be
useful in certain applications such as opening a bank account. But
it is hardly a favorable one in the context of a search engine.
First, a user's interaction with a search engine is usually a
dynamic process. As time goes on, the user's interests may change.
This change may be reflected by the search queries submitted by the
user, or by the user's handling of the search results, or both. The
user's answers to questions on a form tend to become less useful
over time, unless the user chooses to update his answers
periodically. Unlike an occasional update of phone number in the
case of an on-line bank account, frequent updates of a user profile
in the case of a search engine significantly affect its user
friendliness, which is an important consideration when a user
chooses among the search engines currently available. Further, it
is known that users are reluctant to provide explicit feedback,
such as filling out of a form, as many users find it too
burdensome. Thus, while some users may provide explicit feedback on
their interests, it is desirable to have a procedure for implicitly
obtaining information about the user's interests without requiring
any explicit or new actions by the user.
[0031] It is has been observed that a search engine user's past
search activities provide useful hints about the user's personal
search preferences. FIG. 2 provides a list of sources of user
information that are beneficial for user profile construction. For
example, previously submitted search queries 201 are very helpful
in profiling a user's interests. If a user has submitted multiple
search queries related to diabetes, it is more likely than not that
this is a topic of interest to the user. If the user subsequently
submits a query including the term "organic food", it can be
reasonably inferred that he may be more interested in those organic
foods that are helpful in fighting diabetes. Similarly, the
universal resource locators (URL) 203 associated with the search
results in response to the previous search queries and their
corresponding anchor texts 205, especially for search result items
that have been selected or "visited" by the user (e.g., downloaded
or otherwise viewed by the user), are helpful in determining the
user's preferences. When a first page contains a link to a second
page, and the link has text associated with it (e.g., text
neighboring the link), the text associated with the link is called
"anchor text" with respect to the second page. Anchor text
establishes a relationship between the text associated with a URL
link in a document and another document to which the URL link
points. The advantages of anchor text include that it often
provides an accurate description of the document to which the URL
link points, and it can be used to index documents that cannot be
indexed by a text-based search engine, such as images or
databases.
[0032] After receiving search results, the user may click on some
of the URL links, thereby downloading the documents referenced by
those links, so as to learn more details about those documents.
Certain types of general information 207 can be associated with a
set of user selected or use identified documents. For purposes of
forming a user profile, the identified documents from which
information is derived for inclusion in the user profile may
include: documents identified by search results from the search
engine, documents accessed (e.g., viewed or downloaded, for example
using a browser application) by the user (including documents not
identified in prior search results), documents linked to the
documents identified by search results from the search engine, and
documents linked to the documents accessed by the user, or any
subset of such documents.
[0033] The general information 207 about the identified documents
may answer questions such as, what is the format of the document?
Is it in hypertext markup language (HTML), plain text, portable
document format (PDF), or Microsoft Word? What is the topic of the
document? Is it about science, health or business? This information
is also helpful in profiling the user's interests. In addition,
information about a user's activities 209 with respect to the user
selected documents (sometimes herein call the identified
documents), such as how long the user spent viewing the document,
the amount of scrolling activity on the document, and whether the
user has printed, saved or bookmarked the document, also suggests
the importance of the document to the user as well as the user's
preferences. In some embodiments, information about user activities
209 is used both when weighting the importance of information
extracted or derived from the user identified documents. In some
embodiments, information about user activities 209 is used to
determine which of the user identified documents to use as the
basis for deriving the user profile. For example, information 209
may be used to select only documents that received significant user
activity (in accordance with predefined criteria) for generating
the user profile, or information 209 may be used to exclude from
the profiling process documents that the user viewed for less than
a predefined threshold amount of time.
[0034] Finally, the content of the identified documents from
previous search activities is a rich source of information about a
user's interests and preferences. Key terms appearing in the
identified documents and their frequencies with which they appear
in the identified documents are not only useful for indexing the
document, but are also a strong indication of the user's personal
interests, especially when they are combined with other types of
user information discussed above. In one embodiment, instead of the
whole documents, sampled content 211 from the identified documents
is extracted for the purpose of user profile construction, to save
storage space and computational cost. In another embodiment,
various information related to the identified documents may be
classified to constitute category information 213 about the
identified documents. More discussion about content sampling, the
process of identifying key terms in an identified document and the
usage of the category information is provided below.
[0035] Optionally, a user may choose to offer personal information
215, including demographic and geographic information associated
with the user, such as the user's age or age range, educational
level or range, income level or range, language preferences,
marital status, geographic location (e.g., the city, state and
country in which the user resides, and possibly also including
additional information such as street address, zip code, and
telephone area code), cultural background or preferences, or any
subset of these. Compared with other types of personal information
such as a user's favorite sports or movies that are often time
varying, this personal information is more static and more
difficult to infer from the user's search queries and search
results, but maybe crucial in correctly interpreting certain
queries submitted by the user. For example, if a user submits a
query containing "Japanese restaurant", it is very likely that he
may be searching for a local Japanese restaurant for dinner.
Without knowing the user's geographical location, it is hard to
order the search results so as to bring to the top those items that
are most relevant to the user's true intention. In certain cases,
however, it is possible to infer this information. For example,
users often select results associated with a specific region
corresponding to where they live.
[0036] Creating a user profile 230 from the various sources of user
information is a dynamic and complex process. In some embodiments,
the process is divided into sub-processes. Each sub-process
produces one type of user profile characterizing a user's interests
or preferences from a particular perspective. They are:
[0037] a term-based profile 231--this profile represents a user's
search preferences with a plurality of terms, where each term is
given a weight indicating the importance of the term to the
user;
[0038] a category-based profile 233--this profile correlates a
user's search preferences with a set of categories, which may be
organized in a hierarchal fashion, with each category being given a
weight indicating the extent of correlation between the user's
search preferences and the category; and
[0039] a link-based profile 235--this profile identifies a
plurality of links that are directly or indirectly related to the
user's search preferences, with each link being given a weight
indicating the relevance between the user's search preferences and
the link.
[0040] In some embodiments, the user profile 230 includes only a
subset of these profiles 231, 233, 235, for example just one or two
of these profiles. In one embodiment, the user profile 230 includes
a term-based profile 231 and a category-based profile 233, but not
a link-based profile 235.
[0041] In one embodiment, a user profile is created and stored on a
server (e.g., user profile server 108) associated with a search
engine. The advantage of such deployment is that the user profile
can be easily accessed by multiple computers, and that since the
profile is stored on a server associated with (or part of) the
search engine 104, it can be easily used by the search engine 104
to personalize the search results. In another embodiment, the user
profile can be created and stored on the user's computer, sometimes
called the client in a network environment. Creating and storing a
user profile on a user's computer not only reduces the
computational and storage cost for the search engine's servers, but
also satisfies some users' privacy requirements. In yet another
embodiment, the user profile may be created and updated on the
client, but stored on a search engine server. Such embodiment
combines some of the benefits illustrated in the other two
embodiments. A disadvantage of this arrangement is that it may
increase the network traffic between clients and the search engine
servers. It is understood by a person of ordinary skill in the art
that the user profiles of the present invention can be implemented
using client computers, server computers, or both.
[0042] FIG. 3 illustrates an exemplary data structure, a term-based
profile table 300, that may be used for storing term-based profiles
for a plurality of users. Table 300 includes a plurality of records
310, each record corresponding to a user's term-based profile. A
term-based profile record 310 includes a plurality of columns
including a USER_ID column 320 and multiple columns of (TERM,
WEIGHT) pairs 340. The USER_ID column stores a value that uniquely
identifies a user or a group of users sharing the same set of
(TERM, WEIGHT) pairs, and each (TERM, WEIGHT) pair 340 includes a
term, typically 1-3 words long, that is usually important to the
user or the group of users and a weight associated with the term
that quantifies the importance of the term. In one embodiment, the
term may be represented as one or more n-grams. An n-gram is
defined as a sequence of n tokens, where the tokens may be words.
For example, the phrase "search engine" is an n-gram of length 2,
and the word "search" is an n-gram of length 1.
[0043] N-grams can be used to represent textual objects as vectors.
This makes it possible to apply geometric, statistical and other
mathematical techniques, which are well defined for vectors, but
not for objects in general. In the present invention, n-grams can
be used to define a similarity measure between two terms based on
the application of a mathematical function to the vector
representations of the terms.
[0044] The weight of a term is not necessarily a positive value. If
a term has a negative weight, it may suggest that the user prefers
that his search results should not include this term and the
magnitude of the negative weight indicates the strength of the
user's preference for avoiding this term in the search results. By
way of example, for a group of surfing fans at Santa Cruz, Calif.,
the term-based profile may include terms like "surfing club",
"surfing event" and "Santa Cruz" with positive weights. The terms
like "Internet surfing" or "web surfing" may also be included in
the profile. However, these terms are more likely to receive a
negative weight since they are irrelevant and confusing with the
authentic preference of the users sharing this term-based
profile.
[0045] A term-based profile itemizes a user's preference using
specific terms, each term having certain weight. If a document
matches a term in a user's term-based profile, i.e., its content
includes exactly this term, the term's weight will be assigned to
the document; however, if a document does not match a term exactly,
it will not receive any weight associated with this term. Such a
requirement of relevance between a document and a user profile
sometimes may be less flexible when dealing with various scenarios
in which a fuzzy relevance between a user's preference and a
document exists. For example, if a user's term-based profile
includes terms like "Mozilla" and "browser", a document containing
no such terms, but other terms like "Galeon" or "Opera" will not
receive any weight because they do not match any existing term in
the profile, even though they are actually Internet browsers. To
address the need for matching a user's interests without exact term
matching, a user's profile may include a category-based
profile.
[0046] FIG. 4A illustrates a hierarchal category map 400 according
to the Open Directory Project (http://dmoz.org/). Starting from the
root level of map 400, documents are organized under several major
topics, such as "Art", "News", "Sports", etc. These major topics
are often too broad to delineate a user's specific interest.
Therefore, they are further divided into sub- topics that are more
specific. For example, topic "Art" may comprise sub-topics like
"Movie", "Music" and "Literature" and the sub-topic "Music" may
further comprise sub-sub-topics like "Lyrics", "News" and
"Reviews". Note that each topic is associated with a unique
CATEGORY_ID like 1.1 for "Art", 1.4.2.3 for "Talk Show" and 1.6.1
for "Basketball".
[0047] A user's specific interests may be associated with multiple
categories at various levels, each of which may have a weight
indicating the degree of relevance between the category and the
user's interest. In one embodiment, a category-based profile may be
implemented using a Hash table data structure as shown in FIG. 4B.
A category-based profile table 450 includes a table 455 that
comprises a plurality of records 460, each record including a
USER_ID and a pointer pointing to another data structure, such as
table 460-1. Table 460-1 may include two columns, CATEGORY_ID
column 470 and WEIGHT column 480. CATEGORY_ID column 470 contains a
category's identification number as shown in FIG. 4A, suggesting
that this category is relevant to the user's interests and the
value in the WEIGHT column 480 indicates the degree of relevance of
the category to the user's interests.
[0048] A user profile based upon the category map 400 is a
topic-oriented implementation. The items in a category-based
profile can also be organized in other ways. In one embodiment, a
user's preference can be categorized based on the formats of the
documents identified by the user, such as HTML, plain text, PDF,
Microsoft Word, etc. Different formats may have different weights.
In another embodiment, a user's preference can be categorized
according to the types of the identified documents, e.g., an
organization's homepage, a person's homepage, a research paper, or
a news group posting, each type having an associated weight.
Another type category that can be used to characterize a user's
search preferences is document origin, for instance the country
associated with each document's host. In yet another embodiment,
the above-identified category-based profiles may co-exist, with
each one reflecting one aspect of a user's preferences.
[0049] Besides term-based and category-based profiles, another type
of user profile is referred to as a link-based profile. As
discussed above, the PageRank algorithm is based on the link
structure that connects various documents over the Internet. A
document that has more links pointing to it is often assigned a
higher page rank and therefore attracts more attention from a
search engine. Link information related to a document identified by
a user can also be used to infer the user's preferences. In one
embodiment, a list of preferred URLs are identified for a user by
analyzing the frequency of his access to those URLs. Each preferred
URL may be further weighted according to the time spent by the user
and the user's scrolling activity at the URL, and/or other user
activities (209, FIG. 2) when visiting the document at the URL. In
another embodiment, a list of preferred hosts are identified for a
user by analyzing the user's frequency of accessing web pages of
different hosts. When two preferred URLs are related to the same
host the weights of the two URLs may be combined to determine a
weight for the host. In another embodiment, a list of preferred
domains are identified for a user by analyzing the user's frequency
of accessing web pages of different domains. For example, for
finance.yahoo.com, the host is "finance.yahoo.com" while the domain
is "yahoo.com".
[0050] FIG. 5 illustrates a link-based profile using a Hash table
data structure. A link-based profile table 500 includes a table 510
that includes a plurality of records 520, each record including a
USER_ID and a pointer pointing to another data structure, such as
table 510-1. Table 510-1 may include two columns, LINK_ID column
530 and WEIGHT column 540. The identification number stored in the
LINK_ID column 530 may be associated with a preferred URL or host.
The actual URL/host/domain may be stored in the table instead of
the LINK_ID, however it is preferable to store the LINK_ID to save
storage space.
[0051] A preferred list of URLs and/or hosts includes URLs and/or
hosts that have been directly identified by the user. The preferred
list of URLs and/or host may furthermore extend to URLs and/or
hosts indirectly identified by using methods such as collaborative
filtering or bibliometric analysis, which are known to persons of
ordinary skill in the art. In one embodiment, the indirectly
identified URLs and/or host include URLs or hosts that have links
to/from the directly identified URLs and/or hosts. These indirectly
identified URLs and/or hosts are weighted by the distance between
them and the associated URLs or hosts that are directly identified
by the user. For example, when a directly identified URL or host
has a weight of 1, URLs or hosts that are one link away may have a
weight of 0.5, URLs or hosts that are two links away may have a
weight of 0.25, etc. This procedure can be further refined by
reducing the weight of links that are not related to the topic of
the original URL or host, e.g., links to copyright pages or web
browser software that can be used to view the documents associated
with the user selected URL or host. Irrelevant Links can be
identified based on their context or their distribution. For
example, copyright links often use specific terms (e.g., copyright
or "All rights reserved" are commonly used terms in the anchor text
of a copyright link); and links to a website from many unrelated
websites may suggest that this website is not topically related
(e.g., links to the Internet Explorer website are often included in
unrelated websites). The indirect links can also be classified
according to a set of topics and links with very different topics
may be excluded or be assigned a low weight.
[0052] The three types of user profiles discussed above are
generally complimentary to one another since different profiles
delineate a user's interests and preferences from different vantage
points. However, this does not mean that one type of user profile,
e.g., category-based profile, is incapable of playing a role that
is typically played by another type of user profile. By way of
example, a preferred URL or host in a link-based profile is often
associated with a specific topic, e.g., finance.yahoo.com is a URL
focusing on financial news. Therefore, what is achieved by a
link-based profile that comprises a list of preferred URLs or hosts
to characterize a user's preference may also be achievable, at
least in part, by a category-based profile that has a set of
categories that cover the same topics covered by preferred URLs or
hosts.
[0053] It is a non-trivial operation to construct various types of
user profiles that can be stored in the data structures shown in
FIGS. 3-5 based on the user information listed in FIG. 2. Given a
document identified (e.g., viewed) by a user, different terms in
the document may have different importance in revealing the topic
of the document. Some terms, e.g., the document's title, may be
extremely important, while other terms may have little importance.
For example, many documents contain navigational links, copyright
statements, disclaimers and other text that may not be related to
the topic of the document. How to efficiently select appropriate
documents, content from those documents and terms from within the
content is a challenging topic in computational linguistics.
Additionally, it is preferred to minimize the volume of user
information processed, so as make the process of user profile
construction computationally efficient. Skipping less important
terms in a document helps in accurately matching a document with a
user's interest.
[0054] Paragraph sampling (described below with reference to FIG.
6) is a procedure for automatically extracting content from a
document that may be relevant to a user. An important observation
behind this procedure is that less relevant content in a document,
such as navigational links, copyright statements, disclaimer, etc.,
tend to be relatively short segments of text. In one embodiment,
paragraph sampling looks for the paragraphs of greatest length in a
document, processing the paragraphs in order of decreasing length
until the length of a paragraph is below a predefined threshold.
The paragraph sampling procedure optionally selects up to a certain
maximum amount of content from each processed paragraph. If few
paragraphs of suitable length are found in a document, the
procedure falls back to extracting text from other parts of the
document, such as anchor text and ALT tags.
[0055] FIG. 6 is a flowchart illustrating the major steps of
paragraph sampling. Paragraph sampling begins with the step 610 of
removing predefined items, such as comments, JavaScript and style
sheets, etc., from a document. These items are removed because they
are usually related to visual aspects of the document when rendered
on a browser and are unlikely to be relevant to the document's
topic. Following that, the procedure may select the first N words
(or M sentences) at step 620 from each paragraph whose length is
greater than a threshold value, MinParagraphLength, as sampled
content. In one embodiment, the values of N and M are chosen to be
100 and 5, respectively. Other values may be used in other
embodiments.
[0056] In order to reduce the computational and storage load
associated with the paragraph sampling procedure, the procedure may
impose a maximum limit, e.g., 1000 words, on the sampled content
from each document. In one embodiment, the paragraph sampling
procedure first organizes all the paragraphs in a document in
length decreasing order, and then starts the sampling process with
a paragraph of maximum length. It is noted that the beginning and
end of a paragraph depend on the appearance of the paragraph in a
browser, not on the presence of uninterrupted a text string in the
HTML representation of the paragraph. For this reason, certain HTML
commands, such as commands for inline links and for bold text, are
ignored when determining paragraph boundaries. In some embodiments,
the paragraph sampling procedure screens the first N words (or M
sentences) so as to filter out those sentences including
boilerplate terms like "Terms of Service" or "Best viewed", because
such sentences are usually deemed irrelevant to the document's
topic.
[0057] Before sampling a paragraph whose length is above the
threshold value, the procedure may stop sampling content from the
document if the number of words in the sampled content has reached
the maximum word limit. If the maximum word limit has not been
reached after processing all paragraphs of length greater than the
threshold, optional steps 630, 640, 650 and 670 are performed. In
particular, the procedure adds the document title (630), the
non-inline HREF links (640), the ALT tags (650) and the meta tags
(670) to the sampled content until it reaches the maximum word
limit.
[0058] Once the documents identified by a user have been scanned,
the sampled content can be used for identifying a list of most
important (or unimportant) terms through context analysis. Context
analysis attempts to learn context terms that predict the most
important (or unimportant) terms in a set of identified documents.
Specifically, it looks for prefix patterns, postfix patterns, and a
combination of both. For example, an expression "x's home page" may
identify the term "x" as an important term for a user and therefore
the postfix pattern "* home page" can be used to predict the
location of an important term in a document, where the asterisk "*
" represents any term that fits this postfix pattern. In general,
the patterns identified by context analysis usually consist of m
terms before an important (or unimportant) term and n terms after
the important (or unimportant) term, where both m and n are greater
than or equal to 0 and at least one of them is greater than 0.
Typically, m and n are less than 5, and when non-zero are
preferably between 1 and 3. Depending on its appearance frequency,
a pattern may have an associated weight that indicates how
important (or unimportant) the term recognized by the pattern is
expected to be.
[0059] According to one embodiment of the present invention (FIG.
7A), context analysis has two distinct phases, a training phase 701
and an operational phase 703. The training phase 701 receives and
utilizes a list of predefined important terms 712, an optional list
of predefined unimportant terms 714, and a set of training
documents (step 710). In some embodiments, the list of predefined
unimportant terms is not used. The source of the lists 712, 714 is
not critical. In some embodiments, these lists 712, 714 are
generated by extracting words or terms from a set of documents
(e.g., a set of several thousand web pages of high page rank) in
accordance with a set of rules, and then editing them to remove
terms that in the opinion of the editor do not belong in the lists.
The source of the training documents is also not critical. In some
embodiments, the training documents comprise a randomly or
pseudo-randomly selected set of documents already known to the
search engine. In other embodiments, the training documents are
selected from a database of documents in the search engine in
accordance with predefined criteria.
[0060] During the training phase 701, the training documents are
processed (step 720), using the lists of predefined important and
unimportant terms, so as to identify a plurality of context
patterns (e.g., prefix patterns, postfix patterns, and
prefix-postfix patterns) and to associate a weight with each
identified context pattern. During the operational phase 703, the
context patterns are applied to documents identified by the user
(step 730) to identify a set of important terms (step 740) that
characterize the user's specific interests and preferences.
Learning and delineating a user's interests and preferences is
usually an ongoing process. Therefore, the operational phase 703
may be repeated to update the set of important terms that have been
captured previously. This may be done each time a user accesses a
document, according to a predetermined schedule, at times
determined in accordance with specified criteria, or otherwise from
time to time. Similarly, the training phase 701 may also be
repeated to discover new sets of context patterns and to
recalibrate the weights associated with the identified context
patterns.
[0061] Below is a segment of pseudo code that exemplifies the
training phase:
1 For each document in the set { For each improtant term in the
document { For m = 0 to MaxPrefix { For n = 0 to MaxPostfix {
Extract the m words before the important term and the n words after
the important term as s; Add 1 to ImportantContext (m,n,s); } } }
For each unimportant term in the document { For m = 0 to MaxPrefix
{ For n = 0 to MaxPostfix { Extract the m words before the
unimportant term and the n words after the unimportant term as s;
Add 1 to UnimportantContext (m,n,s); } } } } For m = 0 to MaxPrefix
{ For n = 0 to MaxPostfix { For each vaalue of s { Set the weight
for s to a function of ImportantContext (m,n,s), and
UnimportantContext (m,n,s); } } }
[0062] In the pseudo code above, the expression s refers to a
prefix pattern (n=0), a postfix pattern (m=0) or a combination of
both (m>0 & n>0). Each occurrence of a specific pattern
is registered at one of the two multi-dimensional arrays,
ImportantContext(m,n,s) or UnimportantContext(m,n,s). The weight of
a prefix, postfix or combination pattern is set higher if this
pattern identifies more important terms and fewer unimportant terms
and vice versa. Note that it is possible that a same pattern may be
associated with both important and unimportant terms. For example,
the postfix expression "* operating system" may be used in the
training documents 716 in conjunction with terms in the list of
predefined important terms 712 and also used in conjunction with
terms in the list of predefined unimportant terms 714. In this
situation, the weight associated with the postfix pattern "*
operating system" (represented by the expression
Weight(1,0,"operating system")) will take into account the number
of times the postfix expression is used in conjunction with terms
in the list of predefined important terms as well as the number of
times the postfix expression is used in conjunction with terms in
the list of predefined unimportant terms. One possible formula to
determine the weight of a context pattern s is:
Weight(m,n,s)=Log(ImportantContext(m,n,s)+1)-Log(UnimportantContext(m,n,s)-
+1).
[0063] Other weight determination formulas may be used in other
embodiments.
[0064] In the second phase of the context analysis process, the
weighted context patterns are used to identify important terms in
one or more documents identified by the user. Referring to FIG. 7B,
in the first phase a computer system receives training data 750 and
creates a set of context patterns 760, each context pattern having
an associated weight. The computer system then applies the set of
context patterns 760 to a document 780. In FIG. 7B, previously
identified context patterns found within the document 780 are
highlighted. Terms 790 associated with the context patterns are
identified and each such term receives a weight based on the
weights associated with the context patterns. For example, the term
"Foobar" appears in the document twice, in association with two
different patterns, the prefix pattern "Welcome to *" and the
postfix pattern "* builds", and the weight 1.2 assigned to "Foobar"
is the sum of the two patterns' weights, 0.7 and 0.5. The other
identified term "cars" has a weight of 0.8 because the matching
prefix pattern "world's best *" has a weight of 0.8. In some
embodiments the weight for each term is computed using a log
transform, where the final weight is equal to log(initial
weight+1). It is possible that the two terms "Foobar" and "cars"
may not be in the training data 750 and may have never been
encountered by the user before. Nevertheless, the context analysis
method described above identifies these terms and adds them to the
user's term-based profile. Thus, context analysis can be used to
discover terms associated with a user's interests and preferences
even when those terms are not included in a predefined database of
terms.
[0065] As noted, the output of context analysis can be used
directly in constructing a user's term-based profile. Additionally,
it may be useful in building other types of user profiles, such as
a user's category-based profile. For example, a set of weighted
terms can be analyzed and classified into a plurality of categories
covering different topics, and those categories can be added to a
user's category-based profile.
[0066] After executing the context analysis on a set of documents
identified by or for a user, the resulting set of terms and weights
may occupy a larger amount of storage than allocated for each
user's term-based profile. Also, the set of terms and corresponding
weights may include some terms with weights much, much smaller than
other terms within the set. Therefore, in some embodiments, at the
conclusion of the context analysis, the set of terms and weights is
pruned by removing terms having the lowest weights (A) so that the
total amount of storage occupied by the term-based profile meets
predefined limits, and/or (B) so as to remove terms whose weights
are so low, or terms that correspond to older items, as defined by
predefined criteria, that the terms are deemed to be not indicative
of the user's search preferences and interests. In some
embodiments, similar pruning criteria and techniques are also
applied to the category-based profile and/or the link-based
profile.
[0067] In some embodiments, a user's profile is updated each time
the user performs a search and selects at least one document from
the search results to download or view. In some embodiments, the
search engine builds a list of documents identified by the user
(e.g., by selecting the documents from search results) over time,
and at predefined times (e.g., when the list reaches a predefined
length, or a predefined amount of time has elapsed), performs a
profile update. When performing an update, new profile data is
generated, and the new profile data is merged with the previously
generated profile data for the user. In some embodiments, the new
profile data is assigned higher importance than the previously
generated profile data, thereby enabling the system to quickly
adjust a user's profile in accordance with changes in the user's
search preferences and interests. For example, the weights of items
in the previously generated profile data may be automatically
scaled downward prior to merging with the new profile data. In one
embodiment, there is a date associated with each item in the
profile, and the information in the profile is weighted based on
its age, with older items receiving a lower weight than when they
were new. In other embodiments, the new profile data is not
assigned high importance than the previously generated profile
data.
[0068] The paragraph sampling and context analysis methods may be
used independently or in combination. When used in combination, the
output of the paragraph sampling is used as input to the context
analysis method.
[0069] It is further noted that the above-described methods used
for creating user profiles, e.g., paragraph sampling and context
analysis, may be also leveraged for determining the relevance of a
candidate document to a user's preference. Indeed, the primary
mission of a search engine is to identify a series of documents
that are most relevant to a user's preference based on the search
queries submitted by the user as well as the user's user profile.
FIG. 8 illustrates several exemplary data structures that can be
used to store information about a document's relevance to a user
profile from multiple perspectives. For each candidate document,
each identified by a respective DOC_ID, term-based document
information table 810 includes multiple pairs of terms and their
weights, category-based document information table 830 includes a
plurality of categories and associated weights, and link-based
document information table 850 includes a set of links and
corresponding weights.
[0070] The rightmost column of each of the three tables (810, 830
and 850) stores the rank (i.e., a computed score) of a document
when the document is evaluated using one specific type of user
profile. A user profile rank can be determined by combining the
weights of the items associated with a document. For instance, a
category-based or topic-based profile rank may be computed as
follows. A user may prefer documents about science with a weight of
0.6, while he dislikes documents about business with a weight of
-0.2. Thus, when a science document matches a search query, it will
be weighted higher than a business document. In general, the
document topic classification may not be exclusive. A candidate
document may be classified as being a science document with
probability of 0.8 and a business document with probability of 0.4.
A link-based profile rank may be computed based on the relative
weights allocated to a user's URL, host, domain, etc., preferences
in the link-based profile. In one embodiment, term-based profile
rank can be determined using known techniques, such as the term
frequency-inverse document frequency (TF-IDF). The term frequency
of a term is a function of the number of times the term appears in
a document. The inverse document frequency is an inverse function
of the number of documents in which the term appears within a
collection of documents. For example, very common terms like "the"
occur in many documents and consequently as assigned a relatively
low inverse document frequency.
[0071] When a search engine generates search results in response to
a search query, a candidate document D that satisfies the query is
assigned a query score, QueryScore, in accordance with the search
query. This query score is then modulated by document D's page
rank, PageRank, to generate a generic score, GenericScore, that is
expressed as
GenericScore=QueryScore*PageRank.
[0072] This generic score may not appropriately reflect document
D's importance to a particular user U if the user's interests or
preferences are dramatically different from that of the random
surfer. The relevance of document D to user U can be accurately
characterized by a set of profile ranks, based on the correlation
between document D's content and user U's term-based profile,
herein called the TermScore, the correlation between one or more
categories associated with document D and user U's category-based
profile, herein called the CategoryScore, and the correlation
between the URL and/or host of document D and user U's link-based
profile, herein called the LinkScore. Therefore, document D may be
assigned a personalized rank that is a function of both the
document's generic score and the user profile scores. In one
embodiment, this personalized score can be expressed as:
PersonalizedScore=GenericScore*(TermScore+CategoryScore+LinkScore).
[0073] FIGS. 9A and 9B represent two embodiments, both implemented
in a client-server network environment such as the network
environment 100 shown in FIG. 1. In the embodiment shown in FIG.
9A, the search engine 104 receives a search query from a client 102
at step 910 that is submitted by a particular user. In response,
the search engine 104 may optionally generate a query strategy at
step 915 (e.g., the search query is normalized so as to be in
proper form for further processing, and/or the search query may be
modified in accordance with predefined criteria so as to
automatically broaden or narrow the scope of the search query). At
step 920, the search engine 104 submits the search query (or the
query strategy, if one is generated) to the content server 106. The
content server identifies a list of documents that match the search
query at step 920, each document having a generic score that
depends on the document's page rank and the search query. In
general, all the three operations (steps 910, 915 and 920) are
conducted by the search engine system 107, which is on the server
side of the network environment 100. There are two options on where
to implement the operations following these first three steps.
[0074] In some embodiments that employ a server-side
implementation, the user's identification number is embedded in the
search query. Based on the user's identification number, the user
profile server 108 identifies the user's user profile at step 925.
Starting from step 930, the user profile server 108 or the search
engine 104 analyzes each document identified at step 920 to
determine its relevance to the user's profile, creates a profile
score for the identified document at step 935 and then assigns the
document a personalized score that is a function of the document's
generic and profile scores at step 940. At step 942, the user
profile server 108 or the search engine 104 checks whether this the
last one in the list of identified documents. If no, the system
processes the next document in the list. Otherwise, the list of
documents are re-ordered according to their personalized scores and
then sent to the corresponding client from which the user submitted
the search query.
[0075] Embodiments using a client-side implementation are similar
to the server-side implementation, except that after step 920, the
identified documents are sent to the corresponding client from
which the user submitted the query. This client stores the user's
user profile and it is responsible for re-ordering the documents
based upon the user profile. Therefore, this client-side
implementation may reduce the server's workload. Further, since
there is no privacy concern with the client-side implementation, a
user may be more willing to provide private information to
customize the search results. However, a significant limitation to
the client-side implementation is that only a limited number of
documents, e.g., the top 50 documents (as determined using the
generic rank), may be sent to a client for re-ordering due to
limited network bandwidth. In contrast, the server-side
implementation may be able to apply a user's profile to a much
larger number of documents, e.g., 1000, that match the search
query. Therefore, the client-side implementation may deprive a user
access to those documents having relatively low generic ranks, but
significantly high personalized ranks.
[0076] FIG. 9B illustrates another embodiment. Unlike the
embodiment depicted in FIG. 9A, where the search query is not
personalized before submitting the search query to the search
engine 104, a generic query strategy is adjusted (step 965)
according to the user's user profile to create a personalized query
strategy. For example, relevant terms from the user profile may be
added to the search query with associated weights. The creation of
the personalized query strategy can be performed either on the
client side or on the server side of the system. This embodiment
avoids the network bandwidth restriction facing the previous
embodiment. Finally, the search engine 104 submits the personalized
query strategy to the content server 106 (step 970), and therefore
the search results returned by the content server have already been
ordered by the documents' personalized ranks (step 975).
[0077] The profiles of a group of users with related interests may
be combined together to form a group profile, or a single profile
may be formed based on the documents identified by the users in the
group. For instance, several family members may use the same
computer to submit search queries to a search engine. If the
computer is tagged with a single user identifier by the search
engine, the "user" will be the entire family of users, and the user
profile will be represent a combination or mixture of the search
preferences of the various family members. An individual user in
the group may optionally have a separate user profile that
differentiates this user from other group members. In operation,
the search results for a user in the group are ranked according to
the group profile, or according to the group profile and the user's
user profile when the user also has a separate user profile.
[0078] It is possible that a user may switch his interests so
dramatically that his new interests and preferences bear little
resemblance to his user profile, or a user may be temporarily
interested in a new topic. In this case, personalized search
results produced according to the embodiments depicted in FIGS. 9A
and 9B may be less favorable than search results ranked in
accordance with the generic ranks of the documents in the search
results. Additionally, the search results provided to a user may
not include new websites among the top listed documents because the
user's profile tends to increase the weight of older websites which
the user has visited (i.e., older websites from which the user has
viewed or downloaded web pages) in the past.
[0079] To reduce the impact caused by a change in a user's
preferences and interests, the personalized search results may be
merged with the generic search results. In one embodiment, the
generic search results and personalized search results are
interleaved, with the odd positions (e.g., 1, 3, 5, etc.) of a
search results list reserved for generic search results and the
even positions (e.g., 2, 4, 6, etc.) reserved for personalized
search results, or vice versa. Preferably, the items in the generic
search results will not duplicate the items listed in the
personalized search results, and vice versa. More generally,
generic search results are intermixed or interleaved with
personalized search results, so that the items in the search
results presented to the user include both generic and personalized
search results.
[0080] In another embodiment, the personalized ranks and generic
ranks are further weighted by a user profile's confidence level.
The confidence level takes into account factors such as how much
information has been acquired about the user, how close the current
search query matches the user's profile, how old the user profile
is, etc. If only a very short history of the user is available, the
user's profile may be assigned a correspondingly low confidence
value. The final score of an identified document can be determined
as:
FinalScore=ProfileScore*ProfileConfidence+GenericScore*(1-ProfileConfidenc-
e).
[0081] When intermixing generic and personalized results, the
fraction of personalized results may be adjusted based on the
profile confidence, for example using only one personalized result
when the confidence is low.
[0082] Sometimes, multiple users may share a machine, e.g., in a
public library. These users may have different interests and
preferences. In one embodiment, a user may explicitly login to the
service so the system knows his identity. Alternatively, different
users can be automatically recognized based on the items they
access or other characteristics of their access patterns. For
example, different users may move the mouse in different ways, type
differently, and use different applications and features of those
applications. Based on a corpus of events on a client and/or
server, it is possible to create a model for identifying users, and
for then using that identification to select an appropriate "user"
profile. In such circumstances, the "user" may actually be a group
of people having somewhat similar computer usage patterns,
interests and the like.
[0083] Referring to FIG. 10, a personalized search engine system
1000 typically includes one or more processing units (CPU's) 1002,
one or more network or other communications interfaces 1010, memory
1012, and one or more communication buses 1014 for interconnecting
these components. The system 1000 may optionally include a user
interface 1004, for instance a display 1006 and a keyboard 1008.
Memory 1012 may include high speed random access memory and may
also include non-volatile memory, such as one or more magnetic disk
storage devices. Memory 1012 may include mass storage that is
remotely located from the central processing unit(s) 1002. The
memory 1012 preferably stores:
[0084] an operating system 1016 that includes procedures for
handling various basic system services and for performing hardware
dependent tasks;
[0085] a network communication module 1018 that is used for
connecting the system 1000 to other servers or computers via one or
more communication networks (wired or wireless), such as the
Internet, other wide area networks, local area networks,
metropolitan area networks, and so on;
[0086] a system initialization module 1020 that initializes other
modules and data structures stored in memory 1012 required for the
appropriate operation of system 1000;
[0087] a search engine 1022 for processing a search query,
identifying and ordering search results according to the search
query and a user's profile;
[0088] a user profile engine 1030 for gathering and processing user
information, such as the user information identified in FIG. 2, and
creating and updating a user's user profile that characterizes the
user's search preferences and interests; and
[0089] data structures 1040, 1060 and 1080 for storing a plurality
of user profiles.
[0090] The search engine 1022 may further comprise:
[0091] a generic rank module (or instructions) 1024 for processing
a search query submitted by a user, identifying a list of documents
matching the query and assigning each identified document a generic
rank without reference to user specific information;
[0092] a user profile rank module (or instructions) 1026 for
correlating each of a plurality of documents identified by the
generic rank module 1024 with the user's user profile and assigning
the document a profile rank indicating the relevance of the
document to the user's search preferences and interests; and
[0093] a rank mixing module (or instructions) 1028 for combining
the generic rank and the profile rank of an identified document
into a personalized rank and re-ordering the list of documents
according to their personalized ranks.
[0094] In some embodiments, these modules 1024, 1026, 1028 may be
implemented within a single procedure or in a set of procedures
that reside within a single software module.
[0095] The user profile engine 1030 may further comprise:
[0096] a user information collection module 1032 for collecting and
assorting various user information listed in FIG. 2;
[0097] a document content extraction module 1034 for selecting and
extracting content from the documents identified by the user, to
identify content relevant to the user's interests, using techniques
such as paragraph sampling (as discussed above); and
[0098] a context analysis module 1036 for analyzing the content
extracted by the document extraction module 1034 so as to identify
terms that characterize a user's search preferences.
[0099] Each data structure hosting a user profile may further
comprise:
[0100] a data structure 1042, 1062 or 1082 for storing a term-based
user profile;
[0101] a data structure 1044, 1064 or 1084 for storing a
category-based user profile; and
[0102] a data structure 1046, 1066 or 1086 for storing a link-based
user profile.
[0103] The foregoing description, for purpose of explanation, has
been described with reference to specific embodiments. However, the
illustrative discussions above are not intended to be exhaustive or
to limit the invention to the precise forms disclosed. Many
modifications and variations are possible in view of the above
teachings. The embodiments were chosen and described in order to
best explain the principles of the invention and its practical
applications, to thereby enable others skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated.
* * * * *
References