Constraint-based grammars

IPOX constraint-based grammars define:

• categories and features
• macro's
• templates
• initial category
• phrase structure rules
• lexicon

Below, some examples are given of each rule type. The examples serve only as an illustration, they are not intended as an analysis of a particular language.

Categories and features

Word => edge.
   Foot => edge.
   Syl => edge, stress.
   ...
   vow => stress, voc.

   edge => ini, fin.
   voc => grv, rnd, height.

Note: only the complex feature structures edge and voc need a separate definition.

Macro's

FRONT := [voc:[-grv, -rnd]].
   SPREAD := [voc:[+grv, -rnd]].
   ROUND := [voc:[+grv, +rnd]].

   HIGH := [voc:[height=close]].
   MID := [voc:[height=mid]].
   LOW := [voc:[height=open]].

Note: macro's such as these can be used to make a grammar more readable, easier to modify, as well as to express the fact that there are no front, rounded vowels.

Templates

Templates are general descriptions of different kinds of constituents:

• branching constituents
• non-branching constituents
• terminal or empty constituents

   

• constituents with a weak-strong pattern
• constituents with a strong-weak pattern

Branching or non-branching

[edge:[ini=A, fin=B]] --> [edge:[ini=A, -fin]], [edge:[-ini, fin=B]].
   [edge=A] --> [edge=A].
   [stress=A] --> [stress=A].

Weak-strong or strong-weak

[stress=A] --> ([] / [stress=A]).
   [stress=A] --> ([stress=A] \ []).

Note: the feature edge is used to mark the left and right edges of a structure; the feature stress is a head-feature of all categories which define the feature.

Initial category

Word:[edge:[+ini, +fin]].

Note: the top-level goal for the parser; the feature edge is assigned the interpretation of "edge of a word".

Phrase-structure rules

Word --> (Foot / Word).
   Word --> Foot.

   Foot:[edge:[+fin]] --> ((Syl:[+stress] \ Syl:[-stress]) \ Syl:[-stress]).
   Foot --> (Syl:[+stress] \ Syl:[-stress]).
   Foot:[edge:[+ini]] --> Syl.

   Syl --> (On / Ri).
   ... etc.

Notes: in this grammar, the main stress occurs in either the ante-penultimate or the penultimate syllable; a monosyllabic foot is allowed only word-initially.

Lexicon

vow:[FRONT, HIGH] --> "i".
   vow:[-stress, SPREAD, MID] --> "@".

Notes: the macro's are expanded during compilation; if all categories between Syl and vow are defined for the feature stress, the templates will assure that schwa can only occur in unstressed syllables.