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---+Grammar Engineering Frequently Asked Questions

---++Some of my relations/qeqs aren't showing up in the MRS for the whole parse.  Why not?

If relations or qeqs that are contributed by lexical entries or rules are 
not showing up in the MRS for the whole parse, it is almost certainly because
you have a broken [[DiffList][diff-list append]] somewhere in the structure.
The most common way for a diff-list append to break is for one of the arguments
to be underspecified as to its length.  You should check that the =RELS= and
=HCONS= lists inside =CONT= on each lexical entry and the =RELS= and =HCONS=
lists inside =C-CONT= (<b>NB:</b> not =CONT=) of each lexical rule and phrase
structure rule are bounded.  The easiest way to do this is with the =<! !>=
notation:

   * =&lt;! !&gt;= a diff-list with nothing on it.
   * =&lt;! *top* !&gt;= a diff-list with one thing on it.
   * =&lt;! *top*, *top* !&gt;= a diff-list with two things on it.
   * =&lt;! *top*, ... !&gt;= a diff-list with at least one thing on it: <b>underconstrained!</b>
   * =[ LIST.FIRST *top* ]=  a diff-list with *top* as its first thing: <b>underconstrained!</b>

Some of the types defined in =matrix.tdl= already sufficiently specify
the length of the =RELS= and/or =HCONS= lists.  Here is a sample (as of
20-May-2005, courtesy of Jonathan Pool):

   * lexeme-to-word-rule
   * no-ccont-lex-rule
   * basic-head-subj-phrase
   * basic-head-spec-phrase
   * basic-head-comp-phrase
   * basic-head-opt-comp-phrase
   * basic-extracted-comp-phrase
   * extracted-adj-phrase
   * scopal-mod-phrase
   * isect-mod-phrase
   * declarative-clause
   * basic-bare-np-phrase
   * no-hcons-lex-item
   * scopal-mod-lex
   * basic-determiner-lex
   * basic-subord-conjunction-lex
   * single-rel-lex-item

In most cases, your rules and lexical types should inherit from one of
the above.  When they don't, you'll need to be sure to constrain the 
length of the =RELS= and =HCONS= lists.

---+++Related topics

   * [[DiffList][What's a difference list, and why do we use them?]]
   * [[CyclicCheck][The LKB says *"Cyclic check found cycle at ..."*.  What does this mean and how do I debug it?]]

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-- Main.EmilyBender - 18 May 2005, 20 May 2005
Topic revision: r2 - 2005-05-20 - EmilyBender