Computational language: week 9 Finish finite state machines FSA’s for modelling word structure Declarative language models knowledge representation and inheritance non-monotonic or ‘default’ inheritance and lexical knowledge representation multiple inheritance DATR: a lexical knowledge representation language

Finite State Automata Deterministic FSAs An FSA whose recognition behaviour is fully determined by the state it is in and the input symbol it is looking at

Finite State Automata Deterministic FSAs An FSA whose recognition behaviour is fully determined by the state it is in and the input symbol it is looking at Non-deterministic FSAs An FSA with decision points

Finite State Automata Deterministic FSAs Non-deterministic FSAs An FSA with decision points Self-loop may be in a particular state Arcs may have ε transitions

Finite State Automata Formal language Set of strings Finite symbol set, alphabet

Finite State Automata Formal language Set of strings Finite symbol set, alphabet L(m) = {baa!, ba!, baaa!,…} “formal language characterised by m” m = model L = formal language

Finite State Automata Formal language Set of strings Finite symbol set, alphabet L(m) = {baa!, ba!, baaa!,…} A formal language models a fragment of a natural language

Finite state transducers and word structure FSA for word structure Handles the morphotactics Arc labels drawn from sets of lexical classes Lexical entries and affixes in the lexicon Achieve morphological recognition

Finite state transducers and word structure Finite State Transducers for morphological parsing distinction between surface level and lexical level lexical level includes basic stem and morphosyntactic features cat +N+PL -> cats

Finite state transducers and word structure Finite State Transducers for morphological parsing distinction between surface level and lexical level lexical level includes basic stem and morphosyntactic features cat +N+PL -> cats FST: maps one of set of symbols onto another

Finite state transducers and word structure Finite State Transducers for morphological parsing distinction between surface level and lexical level lexical level includes basic stem and morphosyntactic features cat +N+PL -> cats FST: maps one of set of symbols onto another c:c a:a t:t +N:εPL:s

Finite state transducers and word structure Finite State Transducers for morphological parsing Boundary markers: ^ morpheme boundary # word boundary

Finite state transducers and word structure Finite State Transducers for morphological parsing Boundary markers: ^ morpheme boundary # word boundary c:c a:a t:t +N:εPL:^s#

Finite state transducers and word structure Finite State Transducers for morphological parsing Boundary markers: ^ morpheme boundary # word boundary c:c a:a t:t +N:εPL:^s# g:g o:e o:e s:s e:e +N:εPL:#

Knowledge representation Linguistic knowledge Linguistic facts Relations between linguistic facts Computable

Knowledge representation Linguistic knowledge Linguistic facts lexicon Relations between linguistic facts Computable

Knowledge representation Linguistic knowledge Linguistic facts lexicon Relations between linguistic facts inference default inference Computable

Knowledge representation Linguistic knowledge Linguistic facts lexicon Relations between linguistic facts inference default inference Computable DATR Prolog

Knowledge representation and the lexicon Inheritance hierarchy

Knowledge representation and the lexicon Inheritance hierarchy A graphical representation of how facts or properties are shared amongst entities

Knowledge representation and the lexicon Inheritance hierarchy

Knowledge representation and the lexicon Inheritance hierarchy

Knowledge representation and the lexicon Inheritance hierarchy

Knowledge representation and the lexicon Default inheritance hierarchy

Knowledge representation and the lexicon Default inheritance

Knowledge representation and the lexicon Default inheritance

Knowledge representation and the lexicon Default inheritance

Knowledge representation and the lexicon Default inheritance

Knowledge representation and the lexicon DATR, lexical knowledge representation language Inference and default inference Compiled in Prolog Developed by Evans and Gazdar Network Morphology

Knowledge representation and the lexicon DATR demonstration

Lexical knowledge representation Summary Inheritance Inference rules Formalism Computable