[lkb] Debugging trigger rules

[Dan Flickinger]

> Here is an example trigger rule:
> 
> ngurlu-trigger-rule := generator-rule &
>  [ CONTEXT.RELS <! [ ARG1.PNG.PN [ PER excl,
> 				   NUM du ]] !>,
>    FLAGS [ TRIGGER "1du-excl-s-aux" ]].

While I'm not certain of the properties of the MRS-matching step regarding
access to type constraints which would ensure that ARG1 is incompatible
with any of your EPs (like maybe the verb's, if you didn't say that its
EP is an arg1-only-relation), you can avoid this indeterminacy by further 
constraining your rule to insist that the ARG1 be actually instantiated
in the input MRS.  This requirement can be expressed by adding the ARG1 
variable to the FLAGS.EQUAL list of the rule, as follows:

ngurlu-trigger-rule := generator-rule &
 [ CONTEXT.RELS <! [ ARG1 #x1 & 
                          [ PNG.PN [ PER excl,
				     NUM du ]] !>,
   FLAGS [ TRIGGER "1du-excl-s-aux",
           EQUAL < #x1 > ]].

You might for safety also declare the type of that ARG1 to be a referential
index, in order to avoid another source of spurious matching in an input
MRS where you have an EP with an ARG1 which is a handle or an event.

  Dan