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This overview has introduced in a quick and informal way most of the basic aspects and characteristics of Noos. However, not all important aspects of Noos have been explained here. In particular the notion of subsumption between feature terms allow to introduce the notions of unification and antiunification between feature terms. Subsumption is heavily used in taxonomic reasoning, case-based reasoning--and in a variety of inductive learning methods where antiunification also plays an important role. These notions have been skipped in this overview because they require first a more formal explanation of feature terms--see Chapter 3.

Also, the overview has presented the reference/query operator >> (infer-value or ``chip-chip'') and has sketched the reflection engine in Noos. However, there are other references with reflective capabilities that have been omitted. In particular references *>> (all-values), ?>> (exists-value), !>> ( known-value) have been not explained and are to be explained in Chapter 4. Succinctly, the Known-value method establishes a feature value equality only when the feature value is already known (without engaging inference). Exists-value is a query-method that determines whether there is any inferrable value for a given feature of an concept. The result of Exists-value is true if there is at least one method successful in achieving that task, and false otherwise. All-values is a query-method that determines the set of all inferrable values for a given feature of an concept - the set of results of all methods successful in achieving that task. These are powerful reflective constructs that can be used to perform plausible non-monotonic reasoning, planning and other forms of complex reasoning patterns.

Enric Plaza
Thu Jan 23 11:36:28 MET 1997