Linguistics 567: Knowledge Engineering for NLP

Lab 8 Due 2/29

Guest lab instructions provided by Laurie Poulson in consultation with Emily Bender.


Run a baseline test suite

Before making any changes to your grammar for this lab, run a baseline test suite instance. If you decide to add items to your test suite for the material covered here, consider doing so before modifying your grammar so that your baseline can include those examples. (Alternatively, if you add examples in the course of working on your grammar and want to make the snapshot later, you can do so using the grammar you turned in for Lab 7.)


Basic definitions

Common sources

There are many sources of tense and/or grammatical aspect, i.e., possible forms of contributing elements:

Basic Approach

Implementation Specifics


Replace the lexical type hierarchy for finite and nonfinite verbs with lexical rule types (if not already done).

For English, I expanded the hierarchy under form, adding nonfin (nonfinite) with subtypes base (for infinitival forms) and prespart (for present participle forms):

nonfin := form.
base := nonfin.
prespart := nonfin.

Then I wrote lexical rules for finite and nonfinite verbs that specify the FORM values. These lexical rules will function as supertypes for lexeme to word rules and so inherit from lexeme-to-word-rule defined in matrix.tdl.

finite-verb-lex-rule := lexeme-to-word-rule &

nonfinite-verb-lex-rule := lexeme-to-word-rule &
[ DTR.SYNSEM.LOCAL.CAT.HEAD verb & [FORM nonfin]].

I also wrote a rule that defines English infinitival forms (base).

base-verb-lex-rule := nonfinite-verb-lex-rule &

Define tense and aspect values

Define values for the features TENSE and ASPECT in a hierarchy. The specific values possible for these features need to be defined in klingon.tdl. The TENSE and ASPECT features themselves are defined in matrix.tdl as features of the type tam (which is itself the value of the feature E, declared for the type event, i.e., the value of INDEX on verbs). Each particular language may have a different set of values and a different hierarchy. Some languages have more general, and some more specific, contrasts, e.g., [past]/[nonpast] vs. [[farpast/past]/recentpast]/[present/nearfuture/...].

For English, I defined the following tense hierarchy:
nonfuture := tense.
nonpast := tense.
past := nonfuture.
present := nonpast & nonfuture.
future := nonpast.

For English, I defined the following aspect hierarchy:
perfective := aspect.
imperfective := aspect.
progressive := imperfective.
nonprogressive := imperfective.
habitual := nonprogressive.
generic := nonprogressive.

Associate tense and aspect with appropriate forms

Lexically specified

General approach: If aspect is defined on the lexical entries themselves define the aspect directly on the verbs.



If tense and/or aspect is conveyed by inflection on the verb:

General approach: Define the value of tense/aspect in the lexical-rule that licenses the verb.



If tense and/or aspect is conveyed by an auxiliary plus verb form:

General approach: Define the verb forms that are required with the auxiliary including the aspect (or tense, if appropriate) they contribute. Define the auxiliary, including the tense (and/or aspect as appropriate) specifying the required verb type as a complement of the auxiliary. The auxiliary is treated as a head and the verb form as a complement. Their combination is then licensed by the grammar's head-complement rule.



If tense and/or aspect is conveyed by an element that looks like a particle, the implementation depends on the analysis of the particle-like element.

General approach:

Constrain the context for tense and/or aspect

What is necessary to appropriately constrain tense and aspect depends on the particular language.

Two typical scenarios:

Write up

Your write up should address the following phenomena. For each, be sure to include examples in IGT format from your test suite to illustrate your points. (Emily should be able to parse the examples as given to see for herself what your grammar is doing.)

  1. Describe the ways in which tense and aspect is marked in your language and which forms you chose to implement in your grammar.
  2. As best you can, describe the meanings associated with each tense/aspect distinction you implement.  (There might not be much information in your grammar on this point---the author may have just labeled the tense or aspects---but if you can find something, please report it.  We're curious because the terminology is so varied across different works.)
  3. Describe ways in which your language constrains the tense and aspect elements you implemented.
  4. Describe how you implemented tense and aspect in your grammar, including at least:
  5. What difficulties did you encounter (especially if you haven't yet been able to solve them)?
  6. Document what happened when you tested you implementation of tense and aspect, and anything you had to change in your grammar to get them working properly.

Submit your assignment

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ebender at u dot washington dot edu
Last modified: Fri Feb 18 2008 (LAP)