TweetFollow Us on Twitter

Expert Systems
Volume Number:2
Issue Number:3
Column Tag:Lisp Listener

Expert Systems

By John Roy

This month, Mactutors' Lisp Listener has a special exclusive. In the first few installments of the Lisp Listener (nine months ago!) the question of how serious one can be when it comes to AI on the Mac was raised. This month we can be confident in saying that Mac can and is being used for developing real AI applications. Last summer the International Joint Conference on Artificial Intelligence (IJCAI) was the place for the unveiling of a relatively large number of AI related products for the Mac. These included ExperLisp version 1.04, ExperOps5, MacProlog, Macscheme and as you will see in what follows the first serious end user expert system development application. John Roy has written for us a good description of what Nexpert is, what it does, and how it does it.

PROGRAMMING IN NEXPERT

by John Roy

What are Expert Systems?

In one sentence, expert systems are programs that imitate human reasoning. They recognize logical patterns that are similar to those recognized by humans, and then reason with them to produce expert-like performance. The term "expert system" should not be confused with "rule-based system" nor "production system". These latter two terms refer to implementation schemes, which are often used to build expert systems.

The process of capturing expert reasoning is called knowledge engineering. Previously, the knowledge engineer had to analyze a domain of expertise and socraticly refine an expert system based upon that expertise until it performed as well as the human. Eventually, these knowledge engineering pioneers found that declarative (rather than procedural) programming paradigms are more appropriate when writing an expert system.

LISP is used as the foundation of many expert systems because of its pattern matching, language extension, and data typing capabilities. These capabilities allow AI programmers to design declarative structures (which hold the expert's knowledge) and inference engines (which imitate the expert's logic). NEXPERT's AI Kernel was designed in LISP on a Symbolics "LISP Machine" before being ported to the Macintosh.

What is NEXPERT?

NEXPERT is a full blown rule-base development environment for serious knowledge engineering. It is the first rule-base development tool designed specifically for writing expert systems on the Macintosh. It uses if...then...do... rules to represent the domain expert's knowledge. It has many sophisticated aids for rule-base development such as: automatic, graphical knowledge traces (better than those in KEE); automatic forward and backward chaining from the same rules (as in ART); an automatic dialogue system (as in PROLOG); an automatic explanation facility (How, Why, and Apropos); access to external data bases (those in SYLK form); and execution of external, compiled programs (such as those developed in C).

It does not have a frame system, nor automatic belief maintenance. Not incorporating a belief maintenance system was a good idea, since no general theories are available, and each expert system must tailor uncertainty handling to the specific application. However, no frame system access means (1) no object oriented data structures, (2) no message passing, (3) no inheritance of attributes, and (4) instantiation of flavors. Frame systems concern design, maintenance, and manipulation of extremely large data bases. For applications where the data base management system already exists, or for which the data base is small (less than 1000 data values), or for which there is a simple taxonomy, the external SYLK file access and external program execution can easily be used to interface and manipulate the applicable data bases.

Enough introduction, let's get down to business.

Basic NEXPERT Programming.

The Rule Editor, shown in Figure 1, is where you view the rules and choose what operation to perform. By clicking on the dog-ear, the pages can be flipped forward and backward. The rules are alphabetically indexed by Hypothesis (which is how the buttons on the right allow rapid movement through the list). It is a bit difficult to understand the rule-base as a whole from only viewing one rule at a time, but the Network discussed later gives the rule-base developer a global view. There are similar windows (called Notebooks) for the Data List and the Hypothesis List. Selection of a rule-base operation is made by clicking on one of the icons at the bottom of the Rule Editor. From the left they are; (1) create a new rule, (2) modify the current rule, (3) create a new rule by copying the current rule, (4) delete the current rule, and (4) save the knowledge base.

I've found that creating a new rule by copying a similar one, is the best way to go, particularly since all of the rule conditions are ANDed together, and the only way to achieve an OR is to create another rule with the ORed condition modified. This is the same with OPS5, though OPS5 has a MEMBERSHIP operator and NEXPERT does not.

Once an operation has been selected what I call the rule template interface appears. This is the main development interface. One enters and modifies all of the rules from this rule template interface. All you need to do is fill in the conditions, the hypothesis, and the actions via the pop-up menus shown below. Note that currently only eight (8) conditions and actions can be used in a single rule (i.e. # of conditions + # of actions < 9). If the rule had more than eight, then two rules must be written such that they link together and fire in order. One of the nicest, and oddly important, capabilities available are COPY DATA and COPY HYPOTHESIS. These prevent the rule-base developer from re-typing, and more importantly, misspelling data and hypotheses. Note that NEXPERT is case sensitive, and does not allow spaces within the names given to data.

I've pasted this window together so that all of the pop-up menus are visible at once. The basic rule template (underneath the three pop-up menus) consists of the IF slots, the THEN slot, the AND DO slots, and the CONTEXT slots. By clicking on a slot the appropriate menu will pop-up. Don't worry about the context slots right now, they are an advanced programming feature that allow the rule-base developer to suggest knowledge island transitions, (fully explained in a future article, and needed only for extensive rule-bases). The menu at the left shows all of the tests available to form rule conditions (see Table 1). The menu at the right shows all of the actions that can be performed (see Table 2). The menu in the middle (slightly covered by the other previously mentioned menus) is for entering arguments and equations. The COPY DATA and COPY HYPOTHESIS are available from this menu.

Table 1 - Condition Tests

CANCEL do nothing

CLEAR clear test slot

YES and NO test boolean

>, <, , ¾, =, compare numeric equation to constant

NAME declare global synonym

IS and IS compare multi-valued datum to constant

RESET set datum to "unknown"

EQUAL and

UNEQUAL compare two multi-valued data

Table 1 - Action Operations

CANCEL do nothing

CLEAR clear operation slot

DO perform numeric equation and assign to datum

LET assign multi-valued datum a constant

RESET set datum to "unknown"

SHOW either type out a text file to the Apropos Window

or pop-up a paint picture to fill the screen

LOADKB append another knowledge base to current one

EXECUTE perform external function

RETRIEVE load data from an external SYLK file

Once the rule has been entered the OK button will only darken if the rule is structured properly. Clicking on the CHECK button will highlight the offending slot. If the rule is properly structured, but a datum is misused (eg. using a previously defined boolean in an equation), a message will appear (after the OK button-click) explaining the problem. This is very nice most of the time but can be a pain if you decide that you would like to change the data type of a datum.

NEXPERT has two basic values that any datum may have: NOTKNOWN and UNKNOWN. NEXPERT uses UNKNOWN as the "reset" value. Whenever a datum's value is needed and it is currently UNKNOWN, then NEXPERT will switch to backward chaining to attempt to establish a value from the data already available. If this is unsuccessful then the user is queried, via the Question Window, for a value. NOTKNOWN on the other hand, is used to mean that the user has been questioned and does not know the answer. NOTKNOWN allows default reasoning to be done and prevents NEXPERT from continuing to ask for a value that the user does not know.

Knowcessing

"Knowcess" is the term for the rule-based inferencing process. This is where NEXPERT's AI Kernel shows what it is made of. The process can be initiated by suggesting an hypothesis or volunteering a datum. One may also use a combination of the two. If any data is volunteered, then the system will drive forward, attempting to establish as many hypotheses as possible. You can control this forward chaining via NEXPERT's Strategies (see next NEXPERT article for when, why, and how this should be done). If one only suggests an hypothesis, NEXPERT will begin by looking backward in an attempt to find sufficient information that will prove this hypothesis. This information can lead the system to other hypotheses that need to be established, which can lead to others, which lead to others, etc.

Once the system reaches a rule that has some UNKNOWN datum in it, the user will be prompted for a value (see the example in Figure 3 below). At this point the user can access the multi-level Explanation Facility (via the WHY? and HOW? Buttons ), which is automatically built from the static forward and backward chains already in the rule-base. Note that the system knows that the example datum BOSS-CALLED is a boolean and that the user may answer NOTKNOWN. The last button, Apropos, is for tailoring the system to the application even more. When any Apropos Button is clicked on, NEXPERT will bring up the file (text or pictures) that the rule-base developer has made for this datum. This is very useful for instructing the user about the meaning and use of a specific datum.

There are other windows that allow the rule-base developer to watch the progress of the Knowcess. The Transcript Window keeps a complete record of the session, but it slows down the processing by a factor of eight. There is the option to turn the Transcript Window off, which I always use at run-time. The Hypothesis Window displays the hypothesis currently under consideration. And the Conclusions Window reports whether the hypothesis was rejected, established, or underdetermined. But the best way I have found to debug a rule-base is to get a global view.

As I said before, the way to get a global view is from the Network. This is an automatic, dynamic, graphical knowledge trace. Figure 4 shows NEXPERT in the middle of the KNOWCESS process. The dynamics of the system can be followed by noting (a) in this example, the datum TIME points to the hypotheses DAYTIME, NOON, and WORK, (b) that DAYTIME and NOON have already been established, (c) that the system is considering the hypothesis WORK, and (d) that it is currently prompting for the value of the datum BOSS-CALLED (see arrow and bulls-eye in the lower left corner).

Using the operation icons on the left, the rule-base developer can "navigate through the knowledge islands." The functions called by these icons allow investigation of only those areas of the knowledge graphic that are currently of interest. From the top, the operation icons are: (1) single or multiple knowledge island display, (2) display data that point to this hypothesis, (3) display hypotheses that this datum points to, (4) erase this link, (5) focus attention on this datum or hypothesis, and (6) apropos this datum or hypothesis. These operations only affect the display, not the actual knowledge graph of the rule-base. From this one window all of the rules can be viewed, all of the links between rules can be checked, and the dynamics of the Knowcess process can be monitored; making it an excellent aid in the debugging of a rule-base.

Overall, the programming environment of NEXPERT is very clean and efficient. In the next article on NEXPERT I'll be addressing the more complex issues of the AI Kernel, Controlling the Agenda, Customizing the User Interface, Speeding-Up Execution, Outside Database Access, and of course a Full Bug Report.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Top Mobile Game Discounts
Every day, we pick out a curated list of the best mobile discounts on the App Store and post them here. This list won't be comprehensive, but it every game on it is recommended. Feel free to check out the coverage we did on them in the links... | Read more »
Blue Archive heads for nature in New Yea...
Continuing the Blue Archive trend of releasing seasonal events to the Western version of the game nowhere near when they actually happened, the Cyber New Year March update has arrived. It brings with it a story centring around New Year, which it... | Read more »
Once Human conquers maths to be one hotl...
It feels like Once Human has been in development for about ten years at this point, but that has clearly not blunted the excitement for NetEases’ upcoming open-world survival game. As a matter of fact, it seems things have never been better, as... | Read more »
Watcher of Realms celebrates its first a...
It has been one year since Moonton Games kicked off the fantasy RPG Watcher of Realms, and there are a lot of celebrations to mark the occasion. You could take part in a brand-new mode, earn some skins, and recruit some of the strongest characters... | Read more »
Tarisland finally launches and celebrate...
It has felt like a lifetime, as it always does when it comes to waiting, but now Level Infinites’ anticipated MMORPG Tarisland is available across mobiles and Windows. It is time to pick your favourite of the nine classes, customise them to your... | Read more »
Reverse: 1999 offer Reality teams a mout...
Bluepoch Games has confirmed that Phase 2 of Reverse:1999s Version 1.6 has launched, and brings with it a lot to get your teeth into. Along with some sign-in rewards and a bunch of stories to enjoy, as well as a new 6-star character who just might... | Read more »
Uncharted Waters Origin unveils its late...
LINE Games, Motif, and KOEI Tecmo have announced the latest raft of updates for their seafaring adventure title Uncharted Waters Origin, and if you've played for a while you know what to expect. A new Admiral, new mates, and some new story, the... | Read more »
Wrecking Golf is a casual physics-based...
In case you missed it, Dusan Popovic has officially launched Wrecking Golf on iOS and Android, the indie developer's casual golf game on mobile presented with charming pixel-art visuals. Featuring physics-based mechanics and simple controls, the... | Read more »
Blue Archive is striking out to Anime Ex...
At this point in my writing career, I have seen quite a few press releases come about, and it feels like one of the most frequently updated games there is Blue Archive. It is, of course, great to see a game have a life like this, and now Nexon is... | Read more »
Grab a Grammy-inspired Backbone One with...
There are so many mobile controllers on the market that it could be a little difficult to know which to go for. If you are someone who goes for a good old celebrity endorsement, however, then the new Backbone One might be for you, created as it... | Read more »

Price Scanner via MacPrices.net

Walmart continues to sell clearance 13-inch M...
Walmart continues to offer clearance, but new, Apple 13″ M1 MacBook Airs (8GB RAM, 256GB SSD) online for $699, $300 off original MSRP, in Space Gray, Silver, and Gold colors. These are new MacBooks... Read more
Apple is offering steep discounts, up to $600...
Apple has standard-configuration 16″ M3 Max MacBook Pros available, Certified Refurbished, starting at $2969 and ranging up to $600 off MSRP. Each model features a new outer case, shipping is free,... Read more
Save up to $480 with these 14-inch M3 Pro/M3...
Apple has 14″ M3 Pro and M3 Max MacBook Pros in stock today and available, Certified Refurbished, starting at $1699 and ranging up to $480 off MSRP. Each model features a new outer case, shipping is... Read more
Amazon has clearance 9th-generation WiFi iPad...
Amazon has Apple’s 9th generation 10.2″ WiFi iPads on sale for $80-$100 off MSRP, starting only $249. Their prices are the lowest available for new iPads anywhere: – 10″ 64GB WiFi iPad (Space Gray or... Read more
Apple is offering a $50 discount on 2nd-gener...
Apple has Certified Refurbished White and Midnight HomePods available for $249, Certified Refurbished. That’s $50 off MSRP and the lowest price currently available for a full-size Apple HomePod today... Read more
The latest MacBook Pro sale at Amazon: 16-inc...
Amazon is offering instant discounts on 16″ M3 Pro and 16″ M3 Max MacBook Pros ranging up to $400 off MSRP as part of their early July 4th sale. Shipping is free. These are the lowest prices... Read more
14-inch M3 Pro MacBook Pros with 36GB of RAM...
B&H Photo has 14″ M3 Pro MacBook Pros with 36GB of RAM and 512GB or 1TB SSDs in stock today and on sale for $200 off Apple’s MSRP, each including free 1-2 day shipping: – 14″ M3 Pro MacBook Pro (... Read more
14-inch M3 MacBook Pros with 16GB of RAM on s...
B&H Photo has 14″ M3 MacBook Pros with 16GB of RAM and 512GB or 1TB SSDs in stock today and on sale for $150-$200 off Apple’s MSRP, each including free 1-2 day shipping: – 14″ M3 MacBook Pro (... Read more
Amazon is offering $170-$200 discounts on new...
Amazon is offering a $170-$200 discount on every configuration and color of Apple’s M3-powered 15″ MacBook Airs. Prices start at $1129 for models with 8GB of RAM and 256GB of storage: – 15″ M3... Read more
Amazon is offering a $200 discount on 14″ M3...
Amazon has 14-inch M3 MacBook Pros in stock and on sale for $150-$200 off MSRP. Shipping is free. Note that Amazon’s stock tends to come and go, so be sure to check their site often if the model you... Read more

Jobs Board

Solutions Engineer - *Apple* - SHI (United...
**Job Summary** An Apple Solution Engineer's primary role is tosupport SHI customers in their efforts to select, deploy, and manage Apple operating systems and Read more
*Apple* / Mac Administrator - JAMF Pro - Ame...
Amentum is seeking an ** Apple / Mac Administrator - JAMF Pro** to provide support with the Apple Ecosystem to include hardware and software to join our team and Read more
Operations Associate - *Apple* Blossom Mall...
Operations Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Cashier - *Apple* Blossom Mall - JCPenney (...
Cashier - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Blossom Mall Read more
Omnichannel Associate - *Apple* Blossom Mal...
Omnichannel Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.