Lisp Propulsion Laboratory log

Paolo Amoroso's weblog. Main interests: Lisp, astronomy (Moon), space exploration (Apollo and early manned programs)

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Taxonomic reasoning in LISA

Wednesday, September 14, 2005

An interesting feature of LISA (see also my notes) is taxonomic reasoning, i.e. the ability of reasoning over CLOS objects. For example, if you have a rule matching facts that are instances of a base class, with taxonomic reasoning the rule also matches subclasses.

There are a couple of subtle issues. The first is that the LISA manual is currently out of date and states that taxonomic reasoning (see the function consider-taxonomy) is disabled by default. But it is actually enabled by default.

Also, that setting must be changed before the Rete net is created because, as David Young explains, LISA generates closures over, among others, consider-taxonomy. You have to setf consider-taxonomy before defining any rules. If you need to change the setting later in the session, you can probably reinitialize the environment with clear and redefine the rules.