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What is the model?

There are two things which are often referred to as the model. These are:

  1. The textual GRAIL statements containing the information presented by the modeller;
  2. All the concepts and facts implied by that information and the GRAIL rules compiled into a form that they can be manipulated by the GRAIL engine.

In general it is more convenient to speak of a), the text files, as the source files for the model and b) as the compiled model. Exactly how the compiled model is represented, loaded, and saved depends on the implementation.

You look at the source files using a file editor, file list or the GCE Workspace. (The source files are simply text files, and you can, if you wish, edit them with any text editor.) You look at the compiled model using GCE and other GRAIL tools. Information only gets from the source files to the compiled model when you evaluate an expression or expressions in the source files. (Of course you can also evaluate an entire source file or an entire set of source files within the GCE Workspace.)

The GRAIL engine only makes composite categories when it is asked to, since there are a nearly infinite number of possible composite categories which it could make. If you just look at the model using the browser, you will only find those composite categories which have previously been mentioned or requested by a which expression. In the example, we have never mentioned or requested the category (Car which hasOwner Woman). As a result, we will not find it if we look for it by starting with Car in the browser and then expanding to look at all of the kinds of car in the model. However, if we were to evaluate the expression (Car which hasOwner Woman), the GRAIL engine would immediately make the category and classify it in the correct place in the hierarchy.

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