This page discusses the SEM-I.

The SEM-I is a theoretically grounded component of each grammar, capturing several classes of lexical regularities while also serving the crucial engineering function of supplying a reliable and complete specification of the elementary predications the grammar can realize.

For more information see:

SEM-I rational MT: Enriching deep grammars with a semantic interface for scalable machine translation

This page was constructed by FrancisBond, based on information from DanFlickinger and StephanOepen.

The SEM-I in MT

In the transfer process, MRSs are typically checked against the target language SEM-I. This allows you to filter out ill-formed transfers. In batch processing it may save a lot of time to suppress incompatible transfer outputs, as the assumption is they can only fail in generation anyhow. In theory, the SEM-I test can even increase end-to-end coverage, as filtering out incompatible transfer results may allow better MRSs to squeeze into the top-n range that is passed on downstream.

Those that aren't considered compliant will be colored pink in the multi-MRS browser, and should output `invalid output predicate' messages somewhere in the fan-out log (or maybe the :error field of the profile)

The SEM-I test will, by default, reject EPs that lack roles which are not marked as optional in the SEM-I (e.g. the ARG0 of a `compound' relation, which rarely plays a role semantically). It is possible to limit SEM-I comparison to checking the validity of predicates and variable properties by setting the following variable (in the MT package):

 (setf *semi-test* '(:predicates :properties))

This increases coverage considerably for JaEn, and is also the default setting for NoEn.

How to dump a SEM-I

Many sections of the SEM-I need to written manually, such as for variables, roles, and properties. These sections generally go in a top-level file (analogous to 'erg.smi' in the ERG). The predicates section can be dumped from a grammar loaded by the LKB.

In order to dump the predicates, first load the grammar with the LKB, then evaluate the following commands in the Emacs lisp buffer. The following assume the top-level SEM-I is etc/matrix.smi, and the resulting files go under the etc/ grammar subdirectory.

  1. Turn on predicate normalization. This is probably necessary for creating modern (since 2016) SEM-Is. It can also be placed more permanently in lkb/mrsglobals.lsp.

    •    1 (setf *normalize-predicates-p* t)
      
  2. Load the top-level SEM-I file:
    •    1 (setf semi
         2   (mt::construct-semi       
         3    :ids t :rules t :descendp t :embedp t
         4    :semi (mt::read-semi
         5           "etc/matrix.smi"
         6           :includep nil :finalizep nil :recordp nil)
         7    :patches "etc/patches.lisp"
         8    :finalizep t))
      
  3. Dump the predicate hierarchy:
    •    1 (with-open-file
         2     (stream "etc/hierarchy.smi" :direction :output :if-exists :supersede)
         3   (mt::print-semi semi :stream stream :format :hierarchy))
      
  4. Dump the predicates (below they have been separately dumped for abstract and surface predicates)
    •    1 (with-open-file
         2     (stream "etc/abstract.smi" :direction :output :if-exists :supersede)
         3   (mt::print-semi semi :stream stream :format :compact :filter "^[^_]"))
         4 (with-open-file
         5     (stream "etc/surface.smi" :direction :output :if-exists :supersede)
         6   (mt::print-semi semi :stream stream :format :compact :filter "^_"))
      

You can control what information about variables gets dumped with the abstract.vpm. This is loaded in the script file:

(mt:read-vpm (lkb-pathname (parent-directory) "abstract.vpm") :abstract)

Here is an example from the ERG, it deletes unmarked values from the output.

;;;
;;; when creating the SEM-I, ditch a lot of the variable property information,
;;; essentially only keeping what is relevant in terms of the interface.
;;;

GEND : GEND
  m      >> m
  f      >> f
  n      >> n
  m-or-f >> m-or-f
  *      >> !


NUM : NUM
  sg >> sg
  pl >> pl
  *  >> !


IND : IND
  + >> +
  - >> -
  * >> !


TENSE : TENSE
  past   >> past
  pre    >> pres
  fut    >> fut
  *      >> !


MOOD : MOOD 
  subjunctive >> subjunctive
  *           >> !


PROG : PROG
  + >> +
  * >> !


PERF : PERF
  + >> +
  * >> !

RmrsSemi (last edited 2017-04-24 01:34:16 by MichaelGoodman)

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