T

tag

        See part of speech tagging.

        As TAG, it is also an acronym for Tree-Adjoining Grammar. TAGs were not mentioned elsewhere in COMP9414, but are mentioned here just in case you run into them in a book somewhere. 

tagged corpus

    See part of speech tagging.

tense

    The tense of a verb or a sentence relates to the time when the action or state described by the verb or sentence occurred/occurs/will occur. The main contrast with tense is between past, present and future. Most verbs in English indicate the past/present distinction by inflection (a few, like "set", are invariant in this respect). Thus "break" and "breaks" are the present tense forms of the verb "break", and "broke" is the past tense form. The future tense is constructed, in English, by using the auxiliaries "shall" and "will" with the verb - "it will break", for example. Here is a list of the six major tense forms:

    Form Example Meaning

    present He drives a Ford The "drive" action occurs in the present, though

    it suggests that this is habitual - it may have

    occurred in the past and may continue in the future.

    simple past He drove a Ford The action occurred at some time in the past.

    simple future He will drive a Ford The action will occur at some time in the future.

    past perfect

    or pluperfect He had driven a Ford At some time in the past, it was true to say

    "He drove a Ford".

    future perfect He will have driven a Ford At some point in the future, it will be true to say

    "He drove a Ford".

    See also participle.

    Contrast tense, mood and aspect.

term

        Used in the logical form language to describe constants and expressions that describe objects.

        Used in FOPC to refer to a class of objects that may be defined, recursively, as follows:

            a constant is a term;

            a variable is a term;

            a function f applied to a suitable number of terms t1, t2, ..., tn is a term: f(t1, t2, ..., tn). 

        Used to refer to certain types of Prolog language constructs 

terminal symbol

    A terminalsymbol of a grammar is a symbol that can appear in a sentence of the grammar. In effect, a terminalsymbol is a word of the language described by the grammar.

    See also non-terminal symbol and context-free grammar.

the

    The word the gives rise to an important NL quantifier written as THE in Allen or as the or the1 in the Prolog notation used in COMP9414 assignments. Thus the dog barks has logical form:

    (THE d1 : (DOG1 d1) (BARKS1 d1)) (Allen), or

    the(d1 : dog1(d1), barks1(d1)) (COMP9414)

    Here d1 is the variable over which THE quantifies.

    This is also written as (BARKS1 <THE d1 DOG1>) in Allen's notation, and as barks1(the(d1, dog1)) in the Prolog notation.

thematic role

    = semantic case.

theme

    Term used for the noun phrase that follows the verb in an active voice, indicativesentence in English. Also referred to as the object or sometimes the victim.

third person

    One of the choices for the person feature. A sentence is "in the third person" if the subject of the sentence is neither the speaker nor the person(s) addressed, as in "she likes pizza" and "they like pizza".

    "she", "he", "it", and "they" are third-person pronouns, as are "her", "him", and "them". Other words with the third-person feature include "hers", "his", "theirs", "their", "herself", "himself", "itself" and "themselves".

top-down parser

    A parser that starts by hypothesizing an S (see start symbol) and proceeds to refine its hypothesis by expanding S using a grammar rule which has S as its left-hand side (see rewriting process, and successively refining the non-terminals so produced, and so on until there are no non-terminals left (only terminals).

    See also predictive parser.

transitive

    A verb that can take a single syntactic object, like eat, as in "He ate the pizza". Sometimes transitive verbs appear without their object, as in "He ate slowly" - the distinguishing characteristic of transitive verbs is that they can take an object (unlike intransitive verbs, and they cannot take two objects, as ditransitive verbs can. See also subcategorization.

trigram

    A trigram is a triple of things, but usually a triple of lexical categories. Suppose that we are concerned with three lexical categories L1, L2 and L3. The term trigram is used in statistical NLP in connection with the conditionalprobability that a word will belong to L3 given that the preceding words were in L1 and L2. This probability is written Pr(L3 | L2 L1), or more fully Prob(wi ∈ L3 | wi–1 ∈ L2 & wi–2 ∈ L1). For example, in the phrase "The green flies", given that The is tagged with ART, and green with ADJ, we would be concerned with the conditional probabilities Pr(N | ADJ ART) and Pr(V | ADJ ART) given that flies can be tagged with N and V. See also bigram and n-gram.

U

unrestricted grammar

    See Chomsky hierarchy.

V

V

    symbol used in grammar rules for a verb.

var feature

    A feature used as part of the logical form generationsystem described in lectures. It is used to provide a "discourse variable" that corresponds to the constituent it belongs to. It is useful in handling certain types of modifiers - for example, if we have a ball b1 and it turns out to be red, then we can assert (in the logical form for "red ball") that the object is both red and a ball, by including &(ball1(b1), red1(b1)). Grammar rules, once augmented to handle logical forms, usually give explicit instructions on how to incorporate which var feature. For example, the rule for intransitive VPs:

    VP(var(?v), sem(lambda(A2, ?semv(?v, A2))) →

        V(subcat(none), var(?v), sem(?semv))

    indicates that the VPs var feature is derived from that of its V subconstituent and shows how the feature (?v) is also incorporated into the sem of the VP.

    var features are described in Allen on page 268 ff.