Lexical functional grammar and generalized phrase structure grammar

1. Dr.VMS
LFG and GPSG

2. LFG-GPSG
 In LFG one parses sentences and builds up
functional structures, in GPSG sentences are
parsed and translated into formulas of intentional
logic, hardly anyone knows how to generate from
f-structures or from logical formulas

3. LFG
 Lexical Functional Grammar arose in the late
1970’s through the collaboration of Joan Bresnan
(a linguist) and Ronald Kaplan
 Lexical Functional Grammar emphasizes analysis
of certain phenomena in lexical and functional
terms,

4. LFG-Lexical Functional Grammar
 Two levels of structure c and f
 C-structure (tree)
 LFG c-structures adopt the X-bar model of
capturing head-dependent relations, and treat
‘functional’ elements such as Determiners,
Complementizers and Inflections as co-heads of
lexical elements such as Nouns and Verbs. LFG
c-structures however are subject to the lexical
integrity principle which states that minimal c-
structure elements are whole words, not part of
words or empty categories.

5. C Structure

6. F structure
 F-structure (representation of grammatical
functions)
 F-structures capture functional information
and are sets of paired attributes and values
in an attribute-value matrix. Attributes are
morpho-syntactic features (derived from
lexical entries) such as TENSE or
NUMBER, or grammatical functions such as
SUBJECT and OBJECT

7. F Structure

8. Generalized Phrase Structure
Grammar
 Developed by Gazdar, Klein, Pullum and Sag (1985).
 GPSG is confined to be context-free (CF)
 CF phrase structure rules help to efficient parsing in
GPSG
 GPSG divides phrase structure rules into immediate
dominance (ID) rules and linear precedence (LP)
rules
 GPSG provides for a high level, compact
representation of language
 GPSG consists of
 ID-rules, metarules, LP-rules, feature cooccurrence
restrictions (FCRs), and feature specification defaults
(FSDs).

9. GPSG categorisation
Featur
e
Domain Meaning
aux
case
compl
dass
decl
gen
inf
num
pers
prefix
{plus, minus}
{nom, acc,
dat}
{nil, 'zu'}
{plus, minus}
{strong,
mixed,
weak}
{masc, fem,
ntr}
SET OF
VERBS
{sg, pl}
{1, 2, 3}
modals, auxiliaries
nominative, accusative,
dative
complementizer
sub. clause starting with
'dass'
adjective declension
gender
infinitive of a verb
number
person
prefix agreement: verb to
sepref

10. GPSG categorisation
Feature Domain Meaning
prfst
pron
slash
subcat
top
vform
vpos
{sep,
att,
insep,
nopref}
{plus,minus}
SET OF
CATEGORIES
{1, ..., n}
{plus, minus}
{bse,
fin,
psp,
pas }
{first, end}
prefix status: separated
attached
inseparable
no prefix
personal pronoun
slash feature for gap handling
subcategorization of verb
topicalized (fronted)
bare infinitival verb form
finite verb
past participle verb
passive verb
verb-initial or verb-final

11. Pronunciation
 phonology and phonetics which is concerned with
pronunciation.
 Pronunciation of characters in isolation and
combinations
 Regular and irregular pronunciation need
considerations
 some words have the same pronunciation with
different meanings such as "weak" and "week".
Computers cannot differentiate between the two
words

12. Morphology
 structure of words in their written (graphemic) form and
spoken (phonemic) form. It has two forms namely inflection
and derivation.
 Inflection:
 It is related to the grammatical function of words of the
same part of speech;
 e. g. the paradigm of the verb play as:
 Play, plays, played, playing
 Derivation:
 It is related to the production of new words of different parts
of speech;
 e. g. nation - (a noun )
 national- (an adjective )
 nationalize- ( a verb )

13. Morphological Analyser
 A morphological analyzer can extract the base
forms from inserted documents in computers.
 The applications which are achieved in this
respect are:
 a: hyphenation (segmenting words into their
morphs),
 b: spelling correction,
 c: stemming which reduces the related words as
possible. The problem of such computational
programs is the input which should be very broad.
Other forms of application are parsing and
generating natural language utterances in written

14. Syntax
 concerned with the structure of sentences
 Syntax analysis checks the text for
meaningfulness comparing to the rules of formal
grammar.
 Sometimes word order of some kinds of structure
causes misleading-
 Eg. I saw her with a telescope.

15. Semantics
 deals with the meanings of words, phrases and
sentences.
 Single word may have several meanings
 Eg. Chip, well, covers,
 “hot ice-cream” would be rejected by semantic
analyzer based on probability

16. Pragmatics
 deals with the meanings of utterance depending
on the context.
 Interpretation plays crucial role in understanding
the meaning
 Eg. I am waiting
 Can be identified as:
 a.an ordinary fact,
 b. a promise and
 c.a threat.