This is the starting page for documentation about Istar. This documentation explains what Istar is, how it works, how you can use it to build knowledge bases (KB) in the role of a knowledge engineer, and how you can make those KBs available on the World Wide Web as a knowledge service. If your interest is as a user of such KBs (maybe you got here from a link on a page sent by the Istar Knowledge Server) then you are advised to read the more general introduction to Istar.

(Istar is the new name for what used to be called KBTools. KBTools was considered a rather boring name, so we have substituted one that is rather corny, and perhaps cheeky, if you are a Tolkien addict.)


A package for building knowledge based systems and then running them. It is of the inference net kind, with both backward and forward chaining. It is similar to the rule based kind but more flexible.

KBSs make inferences from input information. Usually running them involves asking the user a sequence of questions until enough information is gathered to come up with an answer. Microsoft Wizards are a simple version of this.


There are two levels at which to learn to use Istar as a knowledge engineer: 'driving' the features of the software and using it to do something be useful to you. These are explained in the files:

Read them when you are ready to start. In addition the following files give more detailed information:

There is still much documentation to be written, and not all the facilities of Istar are explained in the above files. But Istar should be reasonably robust, so you can experiment.


# Graphical input. Most KBS software require you to write your rules or inferences using text such as:

IF ?requested_class = PENICILLINS
AND Patients_age >= 0.8*Allowable_age
THEN Patient's age is acceptable for the new drug.

which is sensitive to syntax errors. But with Istar you draw your inference graphically, as boxes and arrows. Then, at your convenience, fill in the detail. A true 'visual programming language'. (Some KBS software such as NExpert can display a box and arrows diagram that has been entered textually, but with Istar the main extry medium is drawing.)

# Smooth user interface. Most software that allows you to draw box and arrows diagrams is clumsy. For instance, to link two boxes:

In Istar you start drawing from edge of Box1, hitting space wherever you want bends and releasing over Box2. No menues or toolbars in sight. The difference is even more marked when you want to redirect a link from one box to another.

# For knowledge generation. This means the user interface actions do not interrupt your flow of thinking as you express your knowledge. Just as "an architect thinks with his pencil" so you can "think with the mouse".

# Easy exploration of KB. Hit 'a' or 'c' over a box, and all others connected to it even indirectly are shown - so you can find out what input information is will have an effect on a given item. Also Find by Name etc.

# Range of types. Normally you are offered integer, float, string and perhaps dates. With Istar you get other types too: probabilities, bayesians, proportions, ratios, odds, directions, and several others. In Istar we attach the semantics to each type (e.g. in ratios and odds, the greatest common divisors are automatically cancelled out). Others to be added soon, such as IFF bitmap, anim, sound sample.

# Range of useful inference methods. Not just add, subtract, multiply, divide, AND, OR, but also things like Chhoser, First-Known, First-OK, Number of Answered, Concatentation, Is-In, etc.

# Kernel written in assembler, for speed and robustness.


The current version of Istar is the current output of a continuing development process. In future you will have scripts, demons, ARexx, dumping of the KB to PROLOG, etc.
Copyright (c) Andrew Basden 1997.

Last updated: 11 September 1999 link to general intro.