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Background of the Invention
The present invention relates to the use of expert systems, in conjunction
with computer aided design systems, for the purpose of designing
integrated circuit devices. More particularly, the invention relates to
refinements in such combined use of expert and computer aided design
systems which ensure an efficient and effective interface with human
operators.
Expert systems have become accepted as tools suitable for assisting circuit
designers in the development of integrated circuit devices. In such
applications of expert systems, the knowledge resident in the expert
system either supplements or supplants the integrated circuit design
capabilities of the human undertaking the actual schematic level
configuration of the integrated circuit device. A representative tool of
such class expert system is describe in PCT International Application No.
PCT/US85/01063 published Dec. 19, 1985, which was identified as
corresponding to U.S. Patent application Ser. No. 06/617,791 filed June 6,
1984. A relatively detailed development of such expert systems, as
elements of a larger technology known as artificial intelligence, is set
forth in the textbook entitle "Understanding Artificial Intelligence",
developed and distributed by Texas Instruments Information Publishing
Center, and having a 1985 copyright date. The latter text identifies and
describes a number of expert systems, including MYCIN, BUGGY, DENDRAL,
Dipmeter Advisor.TM., Internist, ISIS, MACSYMA, MOLGEN, Prospector,
TEIRESIAS, and Explorer.
Diverse video display screen representations, including hierarchically
arranged and overlapping windows, are noted as representative features
available on such expert systems. Typical LISP language based expert
systems incorporate help facilities which provide the human user with a
limited degree of flexibility in interfacing to the computer upon which
the expert system operates. Typical help facilities for video display
interfaces include status lines, help keys, definition or glossary files,
online documentation facilities, and notification windows for special
messages.
The interfaces between human operators and computer aided design systems
per se have been the subject of numerous development efforts.
Representative approaches are disclosed in U.S. Pat. Nos. 4,451,895;
4,613,946 and 4,635,208. In such references, the interaction between a
human and a computer with hierarchical control of the video display
representations are considered in a context lacking expert systems
capabilities. The use of a human interface in conjunction with an expert
system is described as then in existence in the paper authored by Steele,
entitled "An Expert System Application in Semicustom VLSI Design" and
published as paper 35.4 in the Proceedings of the 24th IEEE/ACM Design
Automation Conference of June 28-July 1, 1987.
The relatively recent and rapid advances in the use of computer aided
design systems to develop integrated circuit products, and the coincident
increase in the complexity of the functions and semiconductor design
consideration of such products, have led to a overwhelming need for the
integration of expert system capabilities with computer aided design
system tools. In response to such needs, the joint venture known as
Microelectronics and Computer Technology Corporation (MCC) developed the
inference engine Proteus for representing integrated circuit technology in
a knowledge base. This inference engine and a proprietary knowledge base
were combined with a commercial computer aided design tool using LISP
language code to provide human users with access to the capabilities of
the inference engine and the knowledge base in the course of developing
integrated circuit products. Other knowledge based systems of this class
include R-1, MRS, DUCK/ARBY, EMYCIN, PLANNER and related works at Rutgers
University and Stanford University.
The problem with Proteus and other less sophisticated inference engines
resides in the difficulty of interfacing to a human user who is not
conversant in LISP or other conventional expert system software language.
This difficulty is compounded by the complexity of the integrated circuit
designs which the human users are now routinely implementing in
semiconductor products. The human users are often specialists in a very
narrow class of technology. Consequently, even with the availability of an
integrated circuit design knowledge base and a powerful inference engine,
experience has shown that integrated circuit designers are routinely
incapable of conversing with the inference engine whether directly through
LISP or indirectly through available higher level shell languages.
In the context of such interface difficulties, experience has also shown
that the advice rendered by the expert systems, based upon a circuit
schematic information entered by the human user, is often in a format
which is not readily comprehensible by the human user. Too often the
expert system advice is cryptic from the perspective of the circuit
design. Another somewhat more mundane problem frequently encountered in
the use of expert systems to evaluate integrated circuit designs is
attributable to the relatively long run time exhibited by the expert
system inference engines in the course of exhaustively applying relatively
elaborate knowledge bases to circuit schematics. In such contexts, it is
often valuable to consider incremental expert system advice and to
incorporate interim refinements attributable to such advice. A third and
prevailing problem common of expert systems is the inability to use and
interact with the computer aided design system schematic while considering
the advice issued by the expert system. Integration of the two systems
would be particularly valuable in the context of a video display where the
subject of the advice is schematically represented on the screen
concurrent with the substance of the advice. Such a facility would allow a
technically skilled human user to directly identify and consider the
subject of the advice together with the nature of the deficiency
identified by the expert system. It is these objectives that the present
improvements satisfy in the course of articulating a procedure of suitable
form and content.
SUMMARY OF THE INVENTION
In the context of the problems and objectives set forth hereinbefore, the
invention provides improved processes for interfacing a human user to an
expert system operating in conjunction with computer aided design tools in
the course of designing a complex integrated circuit product. The
processes of the invention have three facets. First, the invention is
directed toward providing expert system advice in formats consistent with
the level of detail desired by the human user. As a second facet, the
invention defines an improved procedure by which expert system advice can
be extracted incrementally. Lastly, the invention defines a process by
which expert system advice and integrated circuit system schematic
information can be portrayed concurrently and in a format consistent with
the human user's capabilities to use the information.
The procedures defined by the invention are preferably implemented by
computer code as prescribed by flow diagram to interface the inference
engine to the video display screen perceivable by the human user. The
procedure includes control code sequences which interact with the computer
aided design system tool in one aspect, and with a menu building code of
the video display interface as a second aspect. Advice formatting proceeds
along three routes depending on whether summary information, brief text,
or full text explanation of the advice is desired. The present invention
also defines a procedure for extracting interim advice. Such extraction
follows a sequence which provides the human user with interim information
corresponding to the advice derived as of the time the expert system is
interrupted. As a last facet, the invention provides a procedure for
merging and concurrently displaying computer aided design system schematic
information with expert system advice through links between the advice
files and the schematic capture files.
These and other features of the invention will be more clearly understood
and appreciated upon considering the detailed description which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representing the general relationships between the
human user, the computer aided design system, the expert system and the
interface by which the entities are linked.
FIG. 2 is a flow diagram schematically illustrating a procedure for
providing advice in different formats.
FIG. 3 is flow diagram schematically representing a method for coupling the
expert system with the integrated circuit schematic representation system.
FIGS. 4 and 5 are flow diagram expansions of blocks within FIG. 3.
FIG. 6 is a schematic illustrating a preferred video screen arrangement for
practicing the process of the invention.
FIGS. 7-12 schematically illustrate selected screen representations from an
integrated circuit design system which combines expert system and computer
aided design system tools.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The improved procedures to which the present invention pertains provide an
integrated circuit designer with a working environment in which the advice
format is selectively detailed, in which the designer may seek advice at
interim stages of the analysis, and in which the designer can concurrently
access both expert advice and schematic information. This is accomplished
in the context of the overall computer aided design system development
setting depicted in FIG. 1. As shown in the figure, human user 1 interacts
through mouse 2 and/or keyboard 3 with computer 4 to obtain on screen 6
the combined expert system and circuit schematic based information.
Conventional use of advanced expert systems require the human user 1
generate LISP or expert system shell language control code to communicate
with the expert system inference engine. The development of the advanced
inference engine Proteus by MCC further burdened the user in that
knowledge of both LISP and Proteus became necessary to effectively use the
expert system. Consequently, there developed the need for a shell
operating procedure suitable for a human user to interface with the expert
system, and the computer aided design system tool, without a prerequisite
working knowledge of LISP or Proteus.
Prior uses of expert systems to help humans design integrated circuit
products required that the human users interact with the expert system
independent of their work on the computer aided design tool. Furthermore,
the advice furnished by the expert system was not only fixed in scope but
relatively cryptic as to particularized explanation. As a third element of
such prior expert systems, interruption of the expert system resulted in a
loss of all advice information. Consequently, the user was often placed in
a position of either allowing the computer to operate for an inordinate
amount of time before concluding that an error had prevented appropriate
operation, or ceased the analysis prematurely but with the recognition
that the complete run will have to be repeated following error analysis.
The structure of LISP code does provide a user with some degree of ability
to track the progress of the expert system computer operation.
The present invention provides an interface 7 which has three procedural
features of particular interest and value for the environments described
above. First, the advice is provided in a format which is variable
according to the desires of the human user. Second, the operational
sequence provides for an interrupt of the expert system analysis, suitable
to return to the previous state as well as to view the results preceding
the interrupt. And lastly, the present interface defines a procedure for
integrating the expert system and computer aided design system to
facilitate human user interplay between related information in each
system. In the context of the representations in FIG. 1, there is now
defined an interface 7 which serves as a shell and link between the video
display user communications medium 6, the Proteus based inference engine
8, the commercially available design tool 9 and the basic menu and
interface code 11, to provide the human user 1 with the three unique and
beneficial capabilities.
In view of the extensive commercial availability and routine use of diverse
design tool code, interface code, and LISP based code suitable to control
expert system inference engines, particularization of such code is neither
practiced nor useful. This is particularly true since the interface
procedure to which the invention pertains is generic as to the application
environments when such environments include the elements of an expert
system, having an inference engine and a knowledge base, a computer aided
design tool system, and some means for communicating with a human user.
Interface 7 of the knowledge base system depicted in FIG. 1 is comprised of
the control code 12, based upon LISP language, which interacts with the
inference engine 8, operated in Proteus language, and further extends to
include the menu building code of interface code character, using PASCAL
language, and design tool code, integrated with a schematic capture tool
program of the computer aided design tool 9.
FIG. 6 illustrates a preferred arrangement of the information displayed on
screen 6 (FIG. 1) during the interaction with the expert system. FIG. 7
provides a representative screen during the start of the interaction
between the human user and the expert system.
The first aspect of the invention relates to the advice format process by
which expert system information is conveyed to the human user, now
available in a form consistent with the ability of the human user to
understand and utilize the information. The flow diagram of the advice
format procedure is depicted in FIG. 2 of the drawings. The entry point
for the procedure coincides with an indication by the expert system that
the advice is available. Thereafter, as shown, the human user selects one
of four options, namely, the "advice summary" format, the "brief all"
format, the "brief prompt" format, or the full text "english translation".
If the summary format is selected, the expert system advice is presented
on screen 6 (FIG. 1) in highly abbreviated form. On the other hand, if the
brief all option is selected, not only is the advice presented in a
somewhat more extensive format, but the advice encompasses all advice
derived during the analysis performed by the expert system. If the brief
prompt format is selected, the human thereafter chooses either a category
of advice or a particular instance of advice to be displayed in the brief
format. As a fourth option available, the human user is provided with an
opportunity to obtain a full english text description of the advice item
and may either obtain a display of the corresponding instance or identify
another advice item by name to produce a corresponding display and further
selection availability.
Representative embodiments of advice items presented in summary format and
brief prompt format are shown as they would appear on a segment of a video
display screen in FIG. 8 of the drawings. The advice in summary format is
shown at the bottom-right, where the advice names and number of
occurrences are identified in summary format. For example, the expert
system has concluded that there exist three occurrences of a risky
situation in which a clock signal is derived rather than being directly
driven from the master. At the top of the display there is shown a
response using the brief prompt format to present the advice corresponding
to the previously noted problem as identified by the expert system. In
this case, the three occurrences are in brief format individually
identified in terms of defect character and circuit location. For example,
as to the second element of advice, the previously noted risky situation
is identified as affecting the two input NAND block numbered I-66. The
brief all option results, as shown in FIG. 9, have all the advice
concurrently represented in brief format. In contrast, the english
translation option would have provided the human user with exhaustive
circuit deficiency information in a terminology suitable for understanding
by a circuit designer of nominal training and experience.
The advice format procedures depicted by flow diagram in FIG. 2 and
illustrated by example in FIG. 8, provide the expert system user with the
flexibility of obtaining and utilizing information in a format having
detail consistent with his or her ability to absorb and use the expert
advice in refining the circuit design. In this way, an inexperienced user
of the expert system is not subjected to a LISP code environment with
cryptic analysis information, while at the same time an experienced user
is not encumbered by lengthy text intended for a neophyte.
FIG. 9 illustrates the use of the brief all format option for the analysis
first shown in FIG. 8, and includes a representative course of dialogue
between the human user and the expert system based upon the advice. The
example presented in FIG. 9 involves a contradiction of ADVICE 5, where
the human user upon understanding the advice given by the expert system
disagrees with the conclusion because of a technical refinement in his
circuit and enters into the record comments suitable to explain his
contradiction of the advice.
As a second and desirable feature of the interface 7 in FIG. 1, the present
procedure contemplates the inclusion of an interrupt within inference
engine 8 suitable to cease further analysis, and, preferably, then store
the existing advice and status data to disk or other file. In the case of
example inference engine 8, a DISKSAVE command in LISP following a
SAVESESSION command from the menu initiates a Proteus subroutine to save
the current state of the advice and the break point in the analysis.
Furthermore, the procedure extracts for consideration the advice generated
prior to the interrupt. The interrupt and restart process as contemplated
by the present invention facilitates shared use of the expert system
together with the earlier noted benefit of accessing interim advice
information from the expert system to identify pervasive deficiencies
early in the analysis.
The third process of the present invention, distinctly suited for use in a
knowledge based integrated circuit design system including an expert
system and a computer aided design tool system, involves the integration
of the advice information with the circuit elements pertaining to such
advice while in a circuit schematic environment. The process begins, as
shown in FIG. 3, with a decision to move into the schematic level as
generated and controlled by the computer aided design system. First, the
availability of expert system advice is verified, irrespective of whether
such advice is derived from an interrupted or completed analysis. The
existence of the related schematic is then verified. Next, data from the
design files is extracted for a successive creation of cross-reference
tables relating the advice and schematic information. The last two steps
of the procedure, creating an advice directory and commencing work at the
schematic level, are individually expanded by step in respective FIGS. 4
and 5.
The procedure for creating an advice directory is shown in FIG. 4 to begin
with the deletion of the previous directory and successive establishment
of a newly identified directory. The new directory relates device
identification or handle information, advice text, and schematic location
information to the previously developed cross-reference table in a file of
key words and advice information. The directory creation procedure is
repeated for each item of advice until all are exhausted. Thereafter,
schematic tool use in the computer aided design system environment
commences, as shown in the sequences of FIGS. 3 and 5, with the generation
of a schematic having advice cross-references.
FIG. 5 shows that if the schematic to which the inquiry is to be directed
already exists in file, only the advice menu needs to be created for
screen display. Otherwise, the schematic representing the circuit segment
subject to the expert system advice is generated and conveyed in
conjunction with the command menu and a constructed advice menu to the
video display.
Exemplary screens from the progression of operations depicted in FIG. 3,
are shown in FIGS. 10, 11 and 12, FIG. 10 illustrates the expert system
screen immediately before entry into the schematic capture tool
environment, the entry being accomplished through the selection of the
NETED function. FIG. 11 illustrates a representative screen while in the
computer aided design system environment which corresponds to the advice
derived from the expert system. For example, the schematic of instance 13
is related to ADVICE 5 involving block I-1464. Concurrently, instance 13
itself is shown in relation to a larger schematic region 14 of the
complete integrated circuit design. ADVICE 5 is now fully developed to
inform the circuit designer that the latch I-1464 is not resettable as
originally designed, and as such is likely to cause function failures in
the overall circuit. While in the environment of the computer aided design
tool, the human user is able to consider the functional elements to which
the advice pertains in both a micro and macro circuit level environment,
to modifying the design in response to a deficiencies identified by the
advice, and to do so in the concurrent presence of the full advice
information. Note in FIG. 12 that one of the command window options
(identified as "Return To Design Advisor") provides a direct path back
into the expert system environment.
In the composite, the various processes defined herein provide the human
user with the flexibility of extracting expert advice at a level of
abstraction consistent with his or her skills, allows the interruption and
use of then available advice, and facilitates the concurrent use of expert
system and computer aided design schematic information.
It will be understood by those skilled in the art that the embodiments
forth hereinbefore are merely exemplary of the numerous arrangements by
which the invention may be practiced, and as such may be replaced by
equivalents without departing from the invention which will now be defined
by appended claims.
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