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RulesLanguage.rst

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Rules definition language

For defining expert system rules there is prepared language. This language should be universal enough for defining all your rules needs. If something missing in the language, please let me know through GIT issue in the repository.

Language is processed with parser and lexer based on antlr4, which gives you many advantages like:

  • Syntax controlling
  • Error messages with bad rules format
  • No need to write own Python parser
  • Create expression tree for easy evaluation of each rule

So when you try to write some rules with bad syntax, you don't need to check it by yourself, parser will tell you about it. Language is described with grammar. In the grammar you should find out, what you can write. Grammar definition is written in atnrl4 language.

Grammar

.. literalinclude:: _static/Rules.g4
   :language: antlr

Examples

Here you can find some examples, about what can be written in the language. It is make no sense to write all possibilities, because there are infinity number of possibilities. It is recommended to look at grammar definition and lear what is possible by that. Here you can find some inspiration. All examples are correct so you can copy them to rule file and execute inference, but you probably don't get any output, because of missing action definition.

Rule with no condition

IF TRUE THEN build_base_random;

Rule with simple condition

IF player_dont_have_base THEN build_base_random;

Parametrized expressions

IF player_dont_have_base THEN build_base 2 2;

Expression with comparision

IF base_count == 0 THEN build_base 2 2;

Expression with comparision and arguments

IF object_count base == 0 THEN build_base 2 2;

Expression with data holder mark and arguments

IF free_position* mountain THAT build_archer free_position;

Logical operators in condition

IF object_count base == 0 AND terrain 2 2 == forest THEN build base 2 2;
IF object_count archer < 2 OR object_count knight < 2 THEN spawn_archer 1 3;

Logical operators in conclusion

IF object_count archer < 2 THEN spawn_archer 1 3 AND spawn_archer 5 5;

Parentheses for logical operators order

IF player_have_base AND ( object_count archer < 2 OR object_count knight < 2 ) THEN spawn_archer 1 3;

Defining value in conclusion

IF object_count archer > 10 THEN strength := 10;
IF object_count archer > 10 THEN strength := high;

Probability of whole rule

IF object_count archer > 10 THEN strength := 10 WITH 0.50;

Probability of condition expressions

IF object_count archer > 10 [0.25] AND object_count knight > 5 [0.8] THEN strength := 10;