U.S. patent number RE38,598 [Application Number 09/779,177] was granted by the patent office on 2004-09-21 for method and system for on demand downloading of module to enable remote control of an application program over a network.
This patent grant is currently assigned to Tridia Corporation. Invention is credited to W. Brian Blevins, Vincent Frese, II, John P. Jarrett.
United States Patent |
RE38,598 |
Frese, II , et al. |
September 21, 2004 |
**Please see images for:
( Reexamination Certificate ) ** |
Method and system for on demand downloading of module to enable
remote control of an application program over a network
Abstract
The system and method is disclosed for remotely controlling an
application program over a network. The system includes an
application interception module and remote display module. The
remote display module is transported across the network and
executed on the user system in response to a user's request to
provide on-demand remote control of an application program. The
application interception module captures an I/O stream generated by
an application program, converts it to remote control protocol
messages and transports them across a network to the remote display
module executing in the user system. The remote display module
converts the remote control protocol messages to system calls
compatible with the operating system environment for the users
computer. Likewise, the remote display module converts system calls
to the local resource interface in the user's computer to remote
control protocol messages which are transported across the network
to the application interception module. The application
interception module interface converts the remote control protocol
messages to system calls for the application program. In this
manner, output from the application program is provided to the
user's computer and input actions at the user's computer are
provided to the application program. Preferably, the remote display
modules and application programs are presented through HTTP servers
over a network to a user's system which uses a browser having a
JAVA interpreter to execute the remote display module and convert
the remote control protocol messages.
Inventors: |
Frese, II; Vincent (Woodstock,
GA), Blevins; W. Brian (Conyers, GA), Jarrett; John
P. (Roswell, GA) |
Assignee: |
Tridia Corporation (Kennesaw,
GA)
|
Family
ID: |
24356752 |
Appl.
No.: |
09/779,177 |
Filed: |
February 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
589136 |
Jan 19, 1996 |
05909545 |
Jun 1, 1999 |
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Current U.S.
Class: |
709/208;
709/229 |
Current CPC
Class: |
G06F
9/44521 (20130101); G06F 9/452 (20180201); G06F
9/45537 (20130101) |
Current International
Class: |
G06F
13/00 (20060101); G06F 15/163 (20060101); G06F
15/16 (20060101); G06F 013/00 (); G06F
015/163 () |
Field of
Search: |
;709/201,202,203,204,205,206,208,209,210,211,217,227,228,229
;707/500,501,526 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Levitt, Jason "Building apps with Navigator," Information Week,
Nov. 6 1995, n.552 p. 88(4): CD. Computer Select 1995.* .
Daniel Garfinkel, Bruce C. Welti, & Thomas W. YIP; HP SharedX:
"A Tool for Real-Time Collaboration", HP Journal Online,
www.hpl.hp.com/hpjournal/94apr/apr94.htm pp 23-36. .
Jan Newmarch: "Embedding of X Applications" University of Canberra,
Australia. .
Daniel Dardailler, "X Over the Web", The X Resource: A Practical
Journal of the X Window System, Issue Fifteen, Pub: Jul. 1995, pp
71-83, Reilly & Associates, Inc. .
Michael A. Dolan et. al., "X Window System Serves in Embedded
Systems,": Computer Society International Conference, IEEE Comp.
Soc. Press., vol. Conf. 35, pp 314-319 (1990). .
James Gosling et al. "The Java Language Environment, " Sun
Delivers, pp 11-18 (1995). .
Catherine A. Wood et. al., "User Interface-Application
Communication in the Chimera User Interface Management System,"
Software Practice & Experience, pp 71-77 (1992). .
Klaus H. Wolf et al., "Multimedia Application Sharing in a
Heterogeneous Environment," Proceedings of ACM Multimedia, US, pp
57-64 (1995). .
Catherine A. Wood et. al. "User Interface Application Linkage,"
Software Practice & Experience, pp 64-84 (1992)..
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Primary Examiner: Dinh; Dung C.
Attorney, Agent or Firm: Mehrman; Michael J. Mehram Law
Office, PC
Claims
What is claimed:
1. A system for on demand remote control of an application program
comprising: an application interception module (AIM) for converting
between a first input/output (I/O) stream protocol used by an
application program and a first remote control protocol, the I/O
stream protocol being used to interface the application program to
local resources on a first computer; and a remote display module
(RDM) for converting between said first remote control protocol and
a second I/O stream protocol, said second I/O stream protocol for
communicating with local resources for a second computer through a
user interface, the remote display module being transported from
said first computer to said second computer for execution by said
second computer upon receipt whereby a user at said second computer
may establish on-demand remote control of the application program
on the first computer to provide input to and view output from the
application program at said first computer.
2. The system of claim 1 further comprising: a remote control
service publisher (RCSP) server for selecting and transporting said
remote display module in response to a user request for an
application program.
3. The system of claim 2 further comprising: a remote application
server (RAS), said remote application server selecting an
application program and corresponding AIM for activation in
response to a request for activation of an application program from
said remote display module, said AIM corresponding to said selected
application program communicating remote control protocol messages
in said remote control protocol with said remote display
module.
4. The system of claim 1 wherein said remote display module is
executed by an interpreter in said second system to open an
application window for said remote display module in said second
computer system.
5. The system of claim 3 further comprising: a browser at said
second computer, said browser communicating with said RCSP to
select and receive said remote display module corresponding to said
requested application program.
6. The system of claim 5 said browser further comprising: an
interpreter for executing said remote display module received from
said RAS.
7. The system of claim 1 further comprising: a protocol translation
and optimization module (PTOM) for converting an I/O stream
encapsulated in a second remote control protocol communicated
between said PTOM and said AIM to said first remote control
protocol.
8. The system of claim 6 wherein said RCSP is a HTTP server and
said remote display module is transported across a network to said
second computer.
9. The system of claim 8 wherein said remote display module is
transported across said network in response to activation of an
applet tag of a HTML document.
10. The system of claim 1 further comprising: a PTOM for reducing
communication latency between said first and said second computers;
and a cache memory coupled to said PTOM, said PTOM retrieving data
about said second computer from remote control protocol messages
from said RDM and storing said data in said cache memory so that
said data about said second computer may be communicated to said
AIM in response to system calls received from said AIM whereby
transmission of said system calls to said second computer are
avoided.
11. A method for providing on demand remote control of an
application program comprising the steps of: transporting a remote
display module from a first computer to a second computer;
executing said remote display module at said second computer to
establish communication between a user interface to computer
resources at said second computer and said first computer through
said remote display module; and launching an application program
and application interception module at said first computer to
establish communication between said application interception
module and said remote display module whereby input/output (I/O)
messages are communicated between said application program and said
user interface at said second computer.
12. The method of claim 11 wherein said remote display module is
transported in an applet file.
13. The method of claim 12 wherein said remote display module is
transported in response to activation of an applet tag of a HTML
document.
14. The method of claim 11 wherein said remote display module is
executed by an interpreter at said second computer.
15. The method of claim 11 further comprising the steps of:
converting I/O messages from said application program to remote
control protocol messages for transmission to said remote display
module at said second computer; and converting remote control
protocol messages received from said application interception
module to I/O messages for said user interface at said second
computer.
16. The method of claim 15 further comprising the steps of:
converting I/O messages from said user interface to remote control
protocol messages for transmission to said application interception
module; and converting remote control protocol messages from said
remote display module to I/O messages for said application
program.
17. The method of claim 11 further comprising the steps of: storing
in a cache memory attribute data from remote control protocol
messages received from said remote display module; and retrieving a
portion of said attribute data from said cache memory in response
to an I/O message from said application program requesting said
attribute data.
18. A method for providing on demand remote control of an
application program, comprising the steps of: determining that a
user at a first computer system desires remote control over an
application at a second computer system; transporting over said
network a remote control module to said .[.second.]. .Iadd.first
.Iaddend.computer when demanded by said user, said remote control
module enabling said first and second computer system to
communicate remotely without pre-installing remote control software
at said .[.second.]. .Iadd.first .Iaddend.computer prior to opening
a communication session between the first and second computer; and
executing said remote control module at said .[.second.].
.Iadd.first .Iaddend.computer to establish a remote control
communication .Iadd.comprising input-output communications
.Iaddend.between a user interface at said first computer and an
application at said second computer. .Iadd.
19. The method of claim 11, wherein the input-output communications
comprise application control commands entered through local
resource at the second computer which are displayed on local
resources at the first computer interacting with a user interface
associated with the application program displayed at the first
computer effecting control over the operation of the application
program..Iaddend..Iadd.
20. The method of claim 19, wherein: the application control
commands entered through local resource at the second computer
comprise mouse and keyboard commands; and the display at the first
computer comprises video and sound output..Iaddend..Iadd.
21. A method for providing on demand remote control of an
application, comprising the steps of: receiving a demand that a
user at a first computer desires remote control over an application
at a second computer; in response to the demand, transmitting a
remote control module to the first computer over a network, and the
remote control module enabling input-output communications allowing
the first computer to remotely control the application at the
second computer system without pre-installing remote control
software at the first computer prior to receiving the remote
control module..Iaddend..Iadd.
22. The method of claim 21, wherein the input-output communications
comprise application control commands entered through local
resource at the first computer which are displayed on local
resources at the second computer interacting with a user interface
associated with the application program displayed at the second
computer effecting control over the operation of the application
program..Iaddend..Iadd.
23. The method of claim 22, wherein: the application control
commands entered through local resource at the first computer
comprise mouse and keyboard commands; and the display at the second
computer comprises video and sound output..Iaddend..Iadd.
24. A system operative to execute the method of claim
21..Iaddend..Iadd.
25. A computer storage medium comprising computer executable
instructions for performing the method of claim
21..Iaddend..Iadd.
26. A method for providing on demand remote control of an
application, comprising the steps of: transmitting from a first
computer a demand indicating that a user at the first computer
desires remote control over an application at a second computer; in
response to the demand, the first computer receiving a remote
control module over a network; the remote control module executing
on the first computer to enable input-output communications
allowing the first computer to remotely control the application at
the second computer system without pre-installing remote control
software at the first computer prior to receiving the remote
control module; and establishing a communication during which the
first computer remotely controls the application running on the
second computer..Iaddend..Iadd.
27. A system operative to execute the method of claim
26..Iaddend..Iadd.
28. A computer storage medium comprising computer executable
instructions for performing the method of claim
26..Iaddend..Iadd.
29. The method of claim 26, wherein the input-output communications
comprise application control commands entered through local
resource at the first computer which are displayed on local
resources at the second computer interacting with a user interface
associated with the application program displayed at the second
computer effecting control over the operation of the application
program..Iaddend..Iadd.
30. The method of claim 29, wherein: the application control
commands entered through local resource at the first computer
comprise mouse and keyboard commands; and the display at the second
computer comprises video and sound output..Iaddend..Iadd.
31. A method for providing on demand remote control of an
application, comprising the steps of: receiving a demand from a
first computer indicating that a user at the first computer desires
remote control over an application at a second computer; in
response to the demand, transmitting to the first computer a remote
control module over a network, and the remote control module
configured to execute on the first computer to enable input-output
communications allowing the first computer to remotely control the
application at the second computer system without pre-installing
remote control software at the first computer prior to receiving
the remote control module..Iaddend..Iadd.
32. A system operative to execute the method of claim
31..Iaddend..Iadd.
33. A computer storage medium comprising computer executable
instructions for performing the method of claim
31..Iaddend..Iadd.
34. The method of claim 31, wherein the input-output communications
comprise application control commands entered through local
resource at the first computer which are displayed on local
resources at the second computer interacting with a user interface
associated with the application program displayed at the second
computer effecting control over the operation of the application
program..Iaddend..Iadd.
35. The method of claim 34, wherein: the application control
commands entered through local resource at the first computer
comprise mouse and keyboard commands; and the display at the second
computer comprises video and sound output..Iaddend..Iadd.
36. A method for providing on demand remote control of an
application, comprising the steps of: receiving a request from a
first computer for remote control of an application at a second
computer, the first computer system receiving and executing an
on-demand remote control module enabling, input-output
communications allowing the first computer to remotely control the
application at the second computer system without pre-installing
remote control software at the first computer prior to receiving
the remote control module; running the application on the second
computer; and the second computer providing the first computer with
remote control access to the application
program..Iaddend..Iadd.
37. A system operative to execute the method of claim
36..Iaddend..Iadd.
38. A computer storage medium comprising computer executable
instructions for performing the method of claim
36..Iaddend..Iadd.
39. The method of claim 36, wherein the input-output communications
comprise application control commands entered through local
resource at the first computer which are displayed on local
resources at the second computer interacting with a user interface
associated with the application program displayed at the second
computer effecting control over the operation of the application
program..Iaddend..Iadd.
40. The method of claim 39, wherein: the application control
commands entered through local resource at the first computer
comprise mouse and keyboard commands; and the display at the second
computer comprises video and sound output..Iaddend..Iadd.
41. A method for providing on demand remote control of an
application, comprising the steps of: receiving a request from a
first computer for remote control of an application at a second
computer; in response to the request, transmitting a remote control
module to the first computer operable for enabling input-output
communications allowing the first computer to remotely control the
application at the second computer system without pre-installing
remote control software at the first computer prior to receiving
the remote control module; executing the remote control module at
the first computer; and establishing a communication during which
the first computer remotely controls the application running on the
second computer..Iaddend..Iadd.
42. A system operative to execute the method of claim
41..Iaddend..Iadd.
43. A computer storage medium comprising computer executable
instructions for performing the method of claim
41..Iaddend..Iadd.
44. The method of claim 41, wherein the input-output communications
comprise application control commands entered through local
resource at the first computer which are displayed on local
resources at the second computer interacting with a user interface
associated with the application program displayed at the second
computer effecting control over the operation of the application
program..Iaddend..Iadd.
45. The method of claim 44, wherein: the application control
commands entered through local resource at the first computer
comprise mouse and keyboard commands; and the display at the second
computer comprises video and sound output..Iaddend.
Description
FIELD OF THE INVENTION
This invention relates to remote execution of computer programs,
and, more particularly, to remote execution of computer programs
over a network.
BACKGROUND OF THE INVENTION
Selling computer software for home and business applications is a
major market. In the retail market, competition is fierce in
getting a program, sometimes called titles, before a consumer to be
considered in the purchasing decision. Shelf space for new titles
is extremely limited and every title for every publisher simply
cannot be displayed. Consequently, software publishers look for
other channels that can be used to get titles before consumers.
One of the other channels used by software publishers or
manufacturers is direct advertising in computer publications.
Another channel is direct marketing to potential consumers of
computer software. However, accurate information about the programs
is difficult to obtain through these channels. For example, the
advertising copy may concentrate on the features provided by the
software and, because space is limited, not disclose all the
hardware and support software required for executing the advertised
program. A review of the program requirements when the user orders
the software or views its packaging at a retail outlet may form an
impression within the consumer that the manufacturer's advertising
was merely hype. This, in turn, may lead the consumer to view
advertising information for all software products with a measure of
skepticism.
In an effort to fully inform the potential purchaser about the
program being offered, some manufacturers offer demonstration
versions of their products. These demonstration versions may
contain prepared examples of the capabilities of the offered
software or they may contain a fully operational version with a
time deactivation feature. The time deactivation feature permits
the program to execute for only a limited time following its
installation. In this manner, the consumer is able to test all of
the features of the software, the ease in which the consumer can
use the software, and the compatibility of the output of the
software with other application programs which the consumer uses on
their system. To disable the time deactivation feature, the
consumer must purchase the software to obtain the commands for
disabling the time deactivation feature or to receive a copy of the
software without the time deactivation feature.
While demonstration software more fully informs consumers about the
capability and user friendliness of the software, it does suffer
from an important limitation--timelines. Many consumers are more
likely to make a purchasing decision favorable to the seller if
they are presented the product when the consumer's interest is
active. If the demonstration version of the program is shipped on a
diskette, the consumer may be busy when it arrives and simply never
attempt to install the demonstration version for evaluation.
Additionally, the consumer may have become aware of another
software product or forthcoming development which the consumer
thinks better addresses the consumer's need. Thus, the opportunity
to favorably impress a consumer may have evaporated by the time the
demonstration software has been placed in the hands of the
consumer.
To make software available more quickly, some manufacturers have
made their demonstration software available through downloading
facilities. To obtain a copy of the software, the consumer's
computer system communicates with the download facility so that a
copy of the program may be transferred through a modem and over a
telephone line to a modem associated with the consumer's system.
While this approach reduces the time between the consumer's request
for the software and its delivery, it still requires the consumer
to contact the download facility for a copy of the program in
response to advertising in a publication. Since the consumer's
computer may not be accessible at the time that the publication is
read, the consumer's interest may wane before she uses her computer
system again.
A promising environment which appears to address many of the timing
problems for the marketing of software is the Internet. The
Internet is a publicly available network of computer networks that
spans, not only the United States, but many parts of the world as
well. To access the information on the Internet, a user uses a
computer coupled to the Internet through an Internet server. These
servers include programs which support the physical, data link,
network and transport layers necessary for communication among the
servers on the Internet. In this way, computers on a network
associated with one server may communicate with a computer
associated with another server and the messages between the
computers may be relayed by intervening servers.
The importance of the Internet as a commercial marketplace was
enhanced by the development of the Hypertext Transport Protocol
(HTTP). This protocol is implemented with the Hypertext Markup
Language (HTML). By using HTTP, documents written in HTML
containing images and text may be presented on a server coupled to
the Internet. The presented documents may then be retrieved and
their contents graphically displayed. To peruse the HTML documents
available through the servers of the Internet, a user's computer
uses an application program called a browser. The browser
communicates with servers using HTML and HTTP to request, retrieve,
and display HTML documents on a user's computer. Such browsers may
also retrieve a HTML document for storage on a user's system. Thus,
a server on the Internet may present information about a software
program in a graphical manner that is as impressive as any print ad
and also support a download of the program to the user's system in
response to a user's request for a demonstration program. Thus, the
viewing of the information that raises a user's interest in a
program in contemporaneous with the user's receipt of the
program.
While the Internet, HTTP and HTML provide a commercially viable
marketplace for software advertising and product demonstration,
there are still limitations that restrain the effectiveness of this
type of marketing once the consumer leaves the manufacturer's
server site with the demonstration product. For one, the consumer
must still install the demonstration product on the consumer's
computer system. To do this, the consumer must still be
knowledgeable about the hardware and software for his computer
system to respond to the information prompts generated by the
installation program for the demonstration product. This
information includes knowledge about system memory, operating
system version, monitor display size and video capability. As a
result, the consumer may not be able to install the demonstration
program properly and the program may abort its execution as a
result. Just as unproductive, the consumer may become so frustrated
during the installation procedure that he simply postpones the
activation of the program and there is no way of ensuring the
consumer later activates the program for the demonstration. Even if
the consumer installs the program with relative ease, the
consumer's unfamiliarity with the capabilities of the demonstrated
program may lead the user to improperly evaluate the program. All
of these possibilities negatively impact the likelihood that a
consumer will make a decision to purchase the software.
One way to overcome the limitations still present in the Internet
environment is to provide the user with access to the application
program without requiring the user to execute the program in her
own computer system. Allowing a user to remotely control an
application on another computer coupled through a network is known
in the software support and maintenance environment. Such remote
control permits a technician located at a customer service site to
execute the application program on a customer's computer from a
remote location to try and duplicate the problem the customer is
experiencing or to examine certain parameters in the program to
ascertain resource problems which may be causing the customer's
problems. Normally, the remote access to the customer's computer is
through a modem and telephone line. That is, the communication is
from one point, the service site, to the other point, the
customer's computer. Other remote control programs may control an
application executing on another computer over a network. One
example of a protocol which supports such remote control over a
network is the X protocol. In this type of control, communication
between the controlling and controlled computers is not necessarily
point to point.
Remote control programs, both network and point-to-point which are
currently known, require a component of the remote control program
to be resident on both computers. That is, the components necessary
to support remote control must be installed on both computers prior
to any attempt to control one of the computers remotely.
Installation of the program to support remote control requires a
consumer knowledgeable about her system parameters or a technician
of the service company who possesses the requisite knowledge. The
system parameters and local resources include the input/output
(I/O) components of the system which, along with the corresponding
support software, form the user interface to the computer system.
These resources include a mouse, keyboard, monitor and
communication ports.
What is needed is a remote control program that does not require
pre-installation in order to operate.
What is needed is a way to provide potential customers with
on-demand access to an application program without requiring the
user to download and install the program on the user's system.
What is needed is a way to use the Internet or other network to
transparently provide demonstration software.
SUMMARY OF THE INVENTION
The limitations of previously known systems have been overcome by a
system and method performed in accordance with the principles of
the present invention. The system includes an application
interception module (AIM) for converting between a first
input/output (I/O) stream protocol used by an application program
and a first remote control protocol, the I/O stream protocol being
used to interface the application program to local resources on a
first computer; and a remote display module for converting between
the first remote control protocol and a second I/O stream protocol
said second I/O stream protocol for communicating with local
resources for a second computer through a user interface, the
remote display module being transported from the first computer to
the second computer for execution by the second computer upon
receipt whereby a user at the second computer may establish
on-demand remote control of the application program on the first
computer to provide input to and view output from the application
program at the first computer.
The method of the present invention includes the steps of
transporting a remote display module from a first computer to a
second computer, executing the remote display module at the second
computer to establish communication between a user interface to
computer resources at the second computer and the first computer
through the remote display module, and launching an application
program and application interception module interface at the first
computer to establish communication between the application
interception module and the remote display module whereby
input/output (I/O) messages are communicated between the
application program and the user interface at the second
computer.
Preferably, a remote control service publisher (RCSP) server, which
is preferably a HTTP server displaying HTML documents, provides
information about the application programs available for use and
demonstration. The HTML documents retrieved from the RCSP contain
tags which may be used by a user at the second computer to send a
request for an application program to the RCSP. Browsers, which are
well known, are used by the second computer to view HTML documents
from the RSCP. In response to an activation request by a user, the
RCSP server sends a file containing the executable code for a
remote display module (RDM) to the browser. Preferably, the browser
includes an interpreter which executes the RDM. This execution
opens an application window for the remote display module and the
remote display module communicates with the local resource
interface in the user's computer. The RDM then sends a request for
activation of the requested application program to a remote
application server (RAS). The RAS launches the requested
application program along with an application interception module
(AIM) and/or a protocol translation and optimization module (PTOM).
The AIM and/or PTOM converts I/O messages in a first I/O stream
protocol for the local resource interface of the computer executing
the application program to remote control protocol messages in a
remote control protocol. The remote display module being executed
by the browser converts the remote control protocol messages it
receives from the AIM and/or PTOM to I/O messages in the second I/O
protocol for delivery to the local resource interface at the user's
computer and converts the user's input captured from the local
resource interface in the user's computer to remote control
protocol messages in the remote control protocol. These remote
control protocol messages are transmitted to the RAS for delivery
to the AIM and/or PTOM for conversion to the first I/O
protocol.
The application interception module (AIM) monitors the system calls
made by the application program to the local resource interface of
the first computer. The local resource interface directs the output
of the application program to local resources, such as a video
display card or sound card, so the program communicates with a
user. The AIM intercepts the system calls of the application
program to the local resource interface and provides the
application program with data from the local resource interface of
a remote computer. The data from the remote local resource
interface is from input devices such as a mouse or keyboard and is
contained within remote control protocol messages. The RAS may also
activate a protocol translation and optimization module (PTOM). The
PTOM is used to encapsulate messages from AIM in a known remote
control protocol within a remote control protocol used for the
remote control protocol messages.
Most preferably, the PTOM is used to reduce the latency in the
communication time associated with networks. Most Internet users
couple to the Internet through a telephone twisted pair line. The
bandwidth for this type of communication conduit is relatively
narrow. To reduce response times, the PTOM has an associated cache
memory in which data about the system in which the RDM is executing
are stored. The PTOM parses system calls received from the AIM to
determine whether the call is requesting information stored in the
cache memory. If the information is stored in the cache memory, the
information is retrieved and returned to the application. In this
way, the time associated with the transmission of the system call
to and the receipt of the response from the RDM is avoided.
Preferably, the RDM of the present invention is implemented in an
interpretative language such as the JAVA language. JAVA capable
browsers include an interpreter for JAVA language instructions.
Thus, an RDM implemented in the JAVA language may be executed by
the interpreter in these JAVA capable browsers. When a JAVA capable
browser is used, the RDM may be identified in an applet tag of a
HTML document. In response to activation of the applet tag, the
RCSP may retrieve the identified file containing the executable
code for the RDM and transfer the file to the JAVA capable browser.
The interpreter in the browser may then execute the transported
RDM. Because the RDM is identified as an application program for
the user's computer, it is provided with its own communication
access to the local resource interface for the user's computer. The
RDM may remain active to present output from the application
program at the RAS to the RDM at the user's computer and to
generate remote control protocol messages corresponding to the
user's input actions for transmission to the AIM or PTOM at the
RAS. When the demonstration is concluded, the RDM at the user's
computer terminates along with its access path to the local
resource interface. Likewise, the RAS terminates the application
program along with any corresponding AIM and PTOM. This preferred
implementation does not require RDMs specifically designed for each
possible operating system environment. Instead, the RDM obtains
sufficient information from the browser and its communication path
to the local resource interface to operate in the user's computer
without pre-installation.
Translation of system calls for one type of operating system to
another type may be performed by the AIM or PTOM. Alternatively,
the system and method of the present invention may maintain a
library of RDMs, each of which is designed for a specific operating
system environment. In response to a request for a program
demonstration, the RCSP selects the file containing the executable
code for the RDM for the operating system environment that
corresponds to the parameters identified in the request for the
program activation received from the user's computer. The file for
the RDM is transmitted and executed in the user's computer. The
execution of the embedded program results in a communication path
to the local resource interface being generated for the RDM. The
RDM then interprets the messages generated by the AIM or PTOM at
the RAS to provide the user access and control of the application
program. This alternative implementation does not require
pre-installation, but does require more operating system parameter
information to correctly select an RDM to transport to the user's
computer.
The system and method of the present invention provides a network
user with access and control over an application program so that
the user may experience the look and feel of the program as well as
try the features of the program. The user need not install any
software or directly supply any information about the user's
computer system to the server through which application access is
possible. Instead, the interface to the application program is
transparent to the user and only requires the execution of a RDM on
the user's machine. The RDM may be provided and used by the user's
computer through the user's browser or through the embedding of a
program segment in the user's computer using an HTML document.
These and other advantages and benefits of the present invention
are evident to one of ordinary skill in the art from the following
detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated and constitute a
part of this specification, illustrate embodiments of the invention
and, together with the general description given above, and the
detailed description of the embodiments given below, serve to
explain the principles of the invention.
FIG. 1 is a block diagram of a system in which the system and
method of the present invention are used to remotely access an
application program;
FIG. 2 is a schematic depiction of the communication layers present
in a network environment for an application program;
FIG. 3 is a block diagram of a protocol translation and
optimization module (PTOM) shown in FIG. 1;
FIG. 4A is a flow chart of the process for providing remote control
access to a user over a network; and
FIG. 4B is a flow chart of the process performed by a PTOM to
reduce latency in communication over a network.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
A system in which the principles of the present invention are
implemented is shown in FIG. 1. The system 10 includes a remote
control service publisher server 12 which is coupled through a
network 14 to a user computer 16. User system 16 may be coupled
through an access server (not shown) such as that provided by a
Internet service provider. Coupled to RCSP 12 and to network 14 is
a remote application server (RAS) 20. Remote application server 20
is used to launch an application program 22 with a corresponding
application interception module (AIM) 24 in response to a request
from user system 16. Normally, application program 22 communicates
with local resource interface 28 using system calls having an I/O
protocol to provide output to and receive input from the I/O device
coupled to the computer on which application program 22 is
executing. RAS 20 may also launch a protocol translation and
optimization module (PTOM) 26 if AIM 24 encapsulates the I/O stream
or system calls of program 22 with a previously known remote
protocol or latency problems are expected with the bandwidth of
network 14. Either AIM 24 or PTOM 26 communicates with user system
16 through network 14. Remote display module (RDM) 18 is
transported from RCSP 12 to user system 16. Once RDM 18 is
executing on user system 16, it provides a seamless and transparent
interface between the local resource interface of system 16 and
application program 22.
User system 16 is typically a personal computer, although other
computer platforms may be used. User system 16 communicates with
servers over network 14 through a communication program such as
browser 30. User system 16 also includes local resource interface
32 which couples application programs on system 16, such as browser
30, to input/output (I/O) devices such as a mouse, keyboard, or
monitor. Local resource interface 32 is sometimes called a user
interface. Application programs executing on user system 16
communicate with local resource interface 32 using system calls
having an I/O protocol. Usually, the I/O protocols of the computer
executing application program 22 and user system 16 are different.
User system 16 may implement any known operating system such as
DOS, DOS with Windows, Windows '95, Unix, O/S 2, or an Apple
operating system. The operating system is used to launch
application programs within user system 16 which process
information and communicate with the user through the devices
coupled to local resource interface 32. Browser 30 is a type of
application program which is used to convert the user's actions
received through local resource interface 32 into commands
recognized for retrieval of information over network 14. Likewise,
browser 30 converts information retrieved through network 14 into a
suitable system calls for displaying the retrieved information
through local resource interface 32 to the user. When network 14 is
the Internet, browser 30 is preferably capable of communicating
over network 14 in the Hypertext Transport Protocol (HTTP). The
documents communicated over the Internet are preferably written in
Hypertext Markup Language (HTML).
RCSP 12 and RAS 20, for Internet applications, are preferably HTTP
servers. That is, the server supports the HTTP communication
protocol for presenting and transmitting HTML documents over the
Internet. Such servers are well known and may be purchased from
such well-known sources as NCSA, NetScape, and CERN. Preferably,
RCSP 12 presents HTML documents which describe the application
programs available for demonstration through RAS 20. A user at
system 16 may retrieve the HTML document using browser 30 and view
the contents of the document through local resource interface 32.
Preferably, the HTML document displaying the information about a
selected application program includes an applet tag field for
activating a demonstration of the application program. When a user
activates the applet tag field, browser 30 transmits a request for
activation of the selected application program along with
attributes and parameters describing the operating system
environment of system 16. Some exemplary applet tags are:
<APP class="rdm" platform="win31" colordepth="8bit">
<APP class="rdm" platform="macros">
<APP class="rdm" platform="pcxserver" colordepth="mono"
transport="winsock"
<APP class="rdm_internet" platform="unix"
browser="netscape">
<APP class="rdm_ether" platform="win95" browser="mosaic">
From these exemplary tags, information about user system 16 is
provided. For example, the "platform" field may identify the user
system 16 as operating under Windows version 3.1, a Macintosh
operating system, X server, Unix operating system, or Windows 95.
Likewise, the color capability, type of browser, or communication
socket may also be identified.
Because the request for a demonstration of an application program
results in the launching of an application program which a user at
system 16 controls. RCSP may include a security component, such as
TCP wrapper available from Wietse Venema of Eindhoven University of
Technology, the Netherlands, which parses the attribute and
parameter information to ascertain information which may be used to
deny access to the application program. In response to an approved
request for application activation, RCSP 12 communicates a RDM 18
to browser 30. RAS 20 may reside on the same computer implementing
RCSP 12 or it may reside on its own computer platform coupled to
RCSP 12 either through a network or dedicated communication line.
RAS 20 preferably includes a library of application programs which
may be made available for demonstration. RAS 20 may also include
additional security components to further scrutinize or interrogate
user system 16 for information prior to launching an application
for use. For example, RAS 20 may, through RDM 18, interrogate a
user for identification and a password prior to providing the user
access to an application program. The application programs which
RAS 20 launches may be launched on the same computer implementing
RAS 20 or RAS 20 may be coupled to a plurality of computers which
may be used to launch one or more application programs. Use of a
plurality of computers for launching application programs 22 is
preferred as each computer may implement a different operating
system environment so that a user may select an application program
which executes under an operating system similar to the one on the
user's system. Alternatively, AIM 24 or PTOM 26 may be used to
translate system calls compatible with the operating system on a
computer executing application program 22 to system calls
compatible with the operating system on a user's system.
RAS 20 launches application programs 22 in an appropriate operating
system environment, whether it is on the computer implementing RAS
20 or one coupled to RAS 20. Each application program 22 has a
corresponding AIM 24 for communicating with the local resource
interface 28 for the computer executing application program 22.
Application interception module 24 of the present invention
captures the I/O stream or system calls between application program
22 and the local resource interface 28 and converts it to a remote
control message in a remote control protocol. For output generated
by application program 22, the remote control protocol messages are
provided to browser 30 of user system 16 for processing in a manner
to be discussed more fully below. PTOM 26 is launched by RAS 20.
AIM 24 uses a known remote protocol not recognized by RDM 18 or the
bandwidth of network 14 may cause latency problems. In the first
situation, PTOM 26 encapsulates the known remote control protocol
messages in the remote control protocol recognized by RDM 18. In
the second case, PTOM 26 allocates a portion of memory as a cache
memory 30 to improve communication turnaround.
An exemplary diagram of the layers and components comprising each
layer for communication between an application program launched by
RAS 20 and a browser 30 at user system 16 is shown in FIG. 2. The
lowest layer is the link layer 50 which is comprised of the
physical hardware and the datalink processing. The physical
component 52 is the actual hardware for communicating a binary bit
stream over a network. Datalink 54 is the processing to organize
the binary bit stream into frames of data for processing by network
layer 58. Network layer 58 includes the processing of the frame
data to deliver data units to the transport layer of a specified
computer. Common network processing includes routing and other
network traffic management. Transport layer 60 communicates
delivered data units to the correct application layer within the
specified computer. For outgoing data, the transport layer provides
sufficient information for the identification of the application
layer in the receiving computer. In Internet applications, the
network layer uses the Internet protocol (IP) and the transport
layer uses the Transport Communication Protocol (TCP). Hence, the
Internet is frequently referred to as a TCP/IP network since these
are the two protocols used to communicate between application
programs and the network hardware.
Application layer 66 is typically comprised of a session component
68, presentation layer 70 and the application program 72. Session
component 68 typically includes software for processing the
interface between a particular user and the application program. In
effect, the session layer is the gateway for a user on the network
to the application program. The presentation layer is the interface
between the application program and the network interface for
network I/O operations. Local resource interface 74 is the
interface between an application program and its corresponding I/O
components or graphical user interface (GUI) on the computer
executing the application program. In the present invention, the
I/O stream between application program 72 and local resource
interface 74 must be captured and communicated to the presentation
layer to transport it across network 14 to another computer, such
as user system 16. Heretofore, the capturing of such an I/O stream
for delivery to another application program has only been possible
if the program for capturing and delivering the I/O stream at each
computer was installed in both computers prior to opening the
communication between both computers. The system and method of the
present invention permit a first computer to initiate communication
with a second computer, transport the program component which
supports remote control between the two computers, activate the
program component and remotely control an application program at
the second computer. This on-demand availability of remote control
over another computer has been heretofore unknown.
The advantages of the present invention are made possible by a
remote display module 18 which is transported from RCSP 12 to user
system 16 prior to the launching of application 22 by RAS 20.
Although other systems are known for transporting I/O streams
across a network, these systems suffer from the limitations that a
component must be installed in a user's system prior to initiation
of the communication for supporting the remote control session. For
example, a protocol known as the X protocol is used for remote
computing across a network. The X protocol captures an I/O stream
between a local resource interface and an application program and
encapsulates it in the transport and network protocol for a
network. The X protocol defines which computer on the network
receives the I/O stream even when the local resource interface of
the computer receiving the I/O stream is the same one in which the
stream was generated. However, for the X protocol to be functional,
a X protocol server must be installed by the user at each computer
on the network in order to enable the computer to receive an I/O
stream from another computer over the network.
In the present invention, there is no user installation of a remote
control component prior to initiating the remote control session.
Instead, RCSP 12, after approving access to an application program
22, selects a corresponding remote display module 18. This remote
display module is communicated through network 14 to browser 30
within user system 16. Preferably, the executable code for the RDM,
which is preferably written in JAVA language, is transported in a
file across network 14 to browser 30 so browser 30 may execute RDM
18 with its internal interpreter. Execution of RDM 18 by the
browser interpreter opens an application window for RDM 18. In this
way, browser 30 opens communication between RDM 18 and local
resource interface 32 to provide user input actions to RDM 18 and
through which RDM 18 may provide output to local resource interface
32. The transporting of the RDM 18 across the network to the
browser for execution does not require any information other than
the identification of the operating system environment for user
system 16 which may be supplied through the applet tag of a HTML
document. This operating system environment identification is used
to select a RDM which best corresponds to the operating system
environment. Specific system parameters required for interfacing
with local resource interface 32 are not required since they are
provided by browser 30. Thus, RDM 18 of the present invention takes
advantage of and supplements the structure present in a JAVA
capable browser to provide seamless and transparent control over an
application program 22 launched by RAS 20.
While browser 30 preferably supports the JAVA language to take
advantage of the interpreter provided within such a browser, other
browser implementations may be used to execute an RDM of the
present invention. For example, a SAFETcl browser may utilize a
mailcap entry to implement a RDM. The mailcap entry correlates the
transported RDM to a file type in the operating system environment
of user system 16. This correlation information may be used to
launch RDM 18 with its own application window so it may communicate
with local resource interface 32 in user system 16. Other schemes
within the principles of the present invention may also be
utilized. For example, information about the operating system
environment for a user system 16 may be provided by a browser 30 in
a Universal Resource Locator (URL) to RCSP 12 for selection of a
corresponding RDM 18. This information may also be provided in a
tag for an extended HTML document. While these implementations are
in accordance with the principles of the present invention in that
no user installation of a RDM is required, these implementations
are designed for specific environments and require more information
for implementation than the above-identified approach used with a
JAVA capable browser.
The system and the method of the present invention may be used to
support the remote control of more than one application program.
For example, RAS 20 may launch an application program and
corresponding AIM 24 and PTOM 26 on one computer and, in response
to another request from a second user, launch a second application
program with its corresponding AIM and PTOM. As long as the
communication capability of the communication server coupling both
computers to the network provides messages to and from the AIMs and
PTOMs for the respective applications in a timely manner, the
operation of the system and method of the present invention remains
the same.
AIM 24 is typically implemented by replacing a component of the
operating system or a component of application program 22. Known
application programs written for the Windows environment execute
system calls to the local resource interface drivers for various
devices or computer resources such as the video system, keyboard,
or mouse. To implement the present invention, AIM 24 traps the
system calls to local resource interface 28 so the data stream
being written to or received from the interface may be captured.
AIM 24 then converts the I/O stream or system calls directed to
local resource interface 28 to remote control protocol messages in
a remote control protocol. The remote control protocol messages are
then encapsulated in the transport, network and link layer
protocols for transporting over the network to RDM 18 within user
system 16. RDM 18 converts these remote control protocol messages
to appropriate applications calls for local resource interface 32
at user system 16. In response to the output generated by the
system calls to local resource interface 32, a user usually
provides data through an input device through local resource
interface 32. RDM 18 captures the system calls from local resource
interface 32 generated by the user's response and converts them to
remote control protocol messages in the remote control protocol
which are likewise encapsulated in transport, network and link
layer protocols for transporting across the network to AIM 24. AIM
24 then converts the remote control protocol messages to system
calls for local resource interface 28. In this way, output from
application program 22 is directed to the local resources available
on user system 16 and user input actions at user system 16 are
provided to application program 22.
PTOM 26 is launched by RAS 20 when AIM 24 includes the capability
of encapsulating an I/O stream in transport and network protocols.
For example, if the application program is written for the X
protocol, AIM 24 already includes the encapsulation of the I/O
stream or system calls in the transport and network protocols. Even
if the I/O stream is directed to the local resource interface in
the computer executing application program 22, it is encapsulated
and decapsulated within the computer prior to being delivered to
local resource interface 28 for the computer executing application
program 22. Although this adds overhead to the processing of the
I/O stream for I/O operations within the computer executing
application program 22, it provides a general scheme which supports
the transporting of the I/O stream across a network. PTOM 26 is
implemented to permit AIM 24 to operate without modification for an
X protocol or other known remote protocol. Instead, PTOM 26 takes
the encapsulated output of AIM 24 and converts it to remote control
protocol messages in the remote control protocol. PTOM 26 also
converts remote control protocol messages from RDM 18 to
encapsulated I/O streams for delivery to AIM 24. When the operating
system environment for user system 16 and the computer executing
application program 22 are not the same, PTOM 26 optimizes the
conversion of the system calls in one system to system calls in the
other system.
For example, because RDM 18 is being executed by browser 30, it may
interrogate browser 30 to obtain parameters regarding the video
system of user system 16. These parameters include the pixel size
of the monitor screen, the color palettes for the screen, and the
fonts supported by the system. These parameters are transmitted to
AIM 24 or PTOM 26 for use. Whenever an system call from application
program 22 is intercepted and provided to AIM 24 or PTOM 26 for
conversion to the remote control protocol, the parameters for user
system 16 are used. For example, if the system call is to a library
routine for drawing a line, AIM 24 or PTOM 26 converts the
parameters for drawing the line so they correspond to the library
routine on user system 16 and correspond to the pixel resolution of
the screen. In this manner, the user at system 16 views the
operation of the application program in a seamless fashion even
though the local resource interfacing at program 22 and user system
are different.
PTOM 26 is required to support the display model for which AIM 24
is designed. That is the system calls and parameters within those
calls used by AIM 24 to drive a display and receive input must be
anticipated by PTOM 26 in order to be able to convert the system
calls received from AIM 24 to remote control protocol messages. The
design of the display which AIM expects may be called the logical
display model for AIM 24. Likewise, RDM 18 conforms its system
calls and corresponding parameters to a logical display model
implemented for it. Thus, PTOM 26 must be designed to map the
system calls and parameters for the logical display model of AIM 24
to the system calls and parameters for the logical display model of
RDM 18. If the system calls or parameters for AIM 24 have
corresponding system calls and parameters in RDM 18, a case
statement for directly mapping the system calls and parameters for
AIM 24 to RDM 18 may be implemented in PTOM 26. In this situation,
RDM 18 may also include a direct mapping of the system calls and
parameters for its logical display model to the corresponding
system calls and parameters for the logical display model of AIM
24.
Where components of the logical display model for AIM 24 do not
have a corresponding element in the logical display model of RDM
18. PTOM 26 must simulate the logical display model for AIM 24.
That is, PTOM 26 must generate responses or provide data parameters
to AIM 24 which conform to the logical display model for AIM 24.
Any changes which should be reflected in the output at user system
16 must be provided in remote control protocol messages to RDM 18.
This may be achieved, for example, by having PTOM 26 maintain a
binary image of the output display or graphical user interface
(GUI) at user system 16. Changes made to this image as a result of
system calls from AIM 24 which do correspond to an system call in
RDM 18 are encapsulated for transport to and displayed at user
system 16.
A block diagram of PTOM 26 is shown in FIG. 3. As shown in the
Fig., PTOM 26 includes a command generator 80, a reply generator 82
and a cache memory 84. The system calls and parameters from AIM 24
may be considered commands and are typically of three types. These
are display instruction commands, status query commands, and
attribute commands. Display instruction commands are instructions
from AIM 24 to its logical display model which change the display
being viewed by a user. Because the attributes of the computer on
which application program 22 is executing and user system 16 may
differ, the system call or parameters of a call which change a
display may need modification prior to be sent to RDM 18.
Attributes are hardware characteristics such as window types, color
encoding schemes, and fonts supported, for example. If the
attribute of the AIM logical display model corresponds to an
attribute in the RDM logical display model, a direct mapping to the
corresponding system call may be used. If the attribute does not
have a corresponding attribute, PTOM 26 may keep a corresponding
bit image of the display or GUI in memory, update it in accordance
with the display instruction command, and send the changed portion
in a remote control message to RDM 18.
A second type of command from AIM 24 is a status query command.
This type of command is used to obtain the characteristics of a
display or GUI or the attribute settings of a computer. If the
characteristic or attribute being queried has a corresponding
attribute or characteristic in RDM 18, a direct mapping is used to
generate the remote control message to RDM 18 requesting the
corresponding attribute or characteristic. Otherwise, PTOM 26
simulates a response consistent with the logical display model of
AIM 24. To reduce communication latency, PTOM 26 may search cache
memory 84 to determine if the attribute or characteristic has been
received from RDM 18 before. If it has and it is stored in cache
84, command generator 80 signals reply generator 82 of PTOM 26 to
retrieve it and incorporate it in a reply to AIM 24.
The third type of command is an attribute command. This type of
command is used to set the attributes of a computer. Again, a
direct mapping may be used if the attribute being set by the
command has a corresponding attribute in RDM 18. If PTOM 26
simulates the attribute, its status is updated in PTOM 26.
Reply remote control protocol messages may be of five types--user
input events, device characteristics, device errors, display model
errors, and attribute status replies. Most user input events from
RDM 18 are capable of direct mapping to a corresponding event in
the logical display model for AIM 24. Events not supported by AIM
24 are ignored. PTOM 26 may process user events to prevent security
breaches in the computer executing application program 22.
Device characteristic and attribute status replies usually are
directly mapped to a reply AIM message since command generator 80
of PTOM 26 only generates remote control protocol messages for
attributes and characteristics in RDM 18 that correspond to AIM 24.
If either type of reply is received which does not correspond to an
attribute or characteristic in AIM 24, it is ignored. Preferably,
the characteristics and attributes received from RDM 18 are also
stored in cache 84 for responding to status query commands without
requiring a message to be sent to RDM 18. Preferably, attributes
and characteristics which conform to the logical display model for
AIM 24 have allocated locations in cache memory 84 to facilitate
their retrieval.
Device errors indicate that a system error occurred at user system
16. PTOM 26 may terminate the remote session in response or it may
pass a corresponding error message to AIM 24, if one can be mapped.
Preferably, application program 22 or PTOM 26 generates a display
instruction command to inform the user of the error. Otherwise, the
user does not understand the unresponsiveness of application
program 22 or its termination. Display model errors occur in
response to compatibility errors between the logical display models
for AIM 24 and PTOM 26. Preferably, PTOM 26 stores such replies in
a log for later analysis.
A method for the remote control of an application program in
accordance with the principles of the present invention is shown in
FIG. 4A. The method begins by the presentation of a document
describing an application program to a browser at a user's system
(Block 100). In response to a user's request for activation of an
application program, RCSP 12 selects a RDM 18 which corresponds to
the parameter and attribute information provided in the application
program request (Block 102). The selected RDM 18 is transported
across the network to the browser in user system 16 and browser 30
launches RDM 18 to establish communication with local resource
interface 32. RAS 20 also launches the requested application
program 22 and any corresponding AIM 24 and PTOM 26, if necessary
(Block 104). The computer executing the requested application
program and user system 16 may now communicate over network 14 with
one another.
The method of FIG. 4A continues by monitoring the application
program calls to its local interface or alternatively, monitoring
the output of AIM 24 for the encapsulated I/O streams. If
application program 22 generates low level I/O calls, AIM 24
converts the I/O streams for the application program's local
resource interface 28 into remote control protocol messages (Block
106). These remote control interface messages are then transported
across network 14 to RDM 18 executing in user system 16 (Block
108). RDM 18 converts the remote control protocol messages to
system calls for the local resource interface 32. RDM 18 also
monitors calls to the local resource interface 32 by input devices
and converts the information in the system calls to remote control
protocol statements for encapsulation in the transport, network and
link layer protocols by browser 30 for transporting across network
14 to AIM 24. AIM 24 then converts the remote control protocol
messages to system calls for application program 22 (Block 110,
112). The conversion between the I/O protocol for the application
program 22 and remote control protocol continues until the program
terminates.
If PTOM 26 is launched with application program 22, it performs the
method shown in FIG. 4B. That method begins by determining whether
the message to be processed is a remote control reply or a remote
control command message (Block 130). If the message is a remote
control reply message, it is converted to an AIM reply for the
application program (Block 132). If the remote control reply
message contains attribute or characteristic information about user
system 16 (Block 134), the data are stored in cache memory 84
(Block 136). The AIM reply is then converted to a system call for
local resource interface 32 by AIM 24 (Block 138). If the message
is a remote control command message, PTOM 20 determines if a
parameter stored in the cache memory is being requested (Block
140). If it is, reply generator 82 retrieves the data from cache 84
and builds an AIM reply message (Block 142). Otherwise, the command
messages are converted to the remote control protocol (Block 144)
and are transmitted across network 14 to user system 16 (Block
146). PTOM 26 continues to convert between the encapsulated system
calls and the remote control protocol until the user terminates the
application program.
In use, after installation of a browser, a user need not install
additional software or provide additional parameters for the remote
control of an application program. Instead, a user browses the
Internet and, if the site browsed is an RCSP, the user selects the
application program. The RCSP transports an RDM to the user system
for execution and the RAS launches an application program in
response to a request from the RDM. The RDM then converts I/O
streams for transporting to the application program launched by the
RAS and the AIM or PTOM corresponding to the launched application
program provides converted I/O streams to RDM 18. In this way,
communication of input and output operations are communicated
between the application program and the user system.
While the present invention has been illustrated by a description
of various embodiments and processes, and while the embodiments and
processes have been described in considerable detail, it is not the
intention of the applicant to restrict or in any way limit the
scope of the appended claims to such detail. Additional advantages
and modifications will readily appear to those skilled in the
art.
* * * * *
References