**5. LOCAL GRAMMARS**

There are phenomena of variation of form which are best treated by finite
automata (DAGs). We mention a few examples:

- Variations of form for a given technical term, that morphological
variation and/or abbreviations. The first two graphs given in annex 3 provide
examples of this very common situation (technical terms: *perfect Penrose tiling
system* and *insuffisance de la glande thyroïde*)

Is is important to notice that the variants of a given technical text can be
seen as constituting an equivalence class of forms for the term. In principle,
the variants are all synonymous. Hence, it is possible to add to the graph paths
occupied by synonyms unrelated in form to the variants, which is about what
happens with *hypothyroidy*. These equivalence classes could constitute a basis
for constructing new types of thesaurus, well adapted to applications such as
information retrieval.

- A common use of local grammars is for semi productive sets of expressions,
apparented in shape and meaning. We give the following examples in annex 3:

names of oceans in French,
two families of dates in English: rounded and numerical dates,
a family of terms of weight in French.
- Local grammars can also be used for the detection of new terms, especially
in the case of compound utterances. The last two graphs of the annex 3 are
grammatical graphs that represent forms of compound nouns built by means of
nouns and agreeing adjectives, we give the graph of binary terms and the graph
of ternary forms.

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