ling 581: advanced computational linguistics lecture notes march 23rd
TRANSCRIPT
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LING 581: Advanced Computational Linguistics
Lecture NotesMarch 23rd
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Administrivia
• Welcome back!• Task 3 is due
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Homework Task
Treebank• There are 180487 VPs in the
Wall Street Journal section• Q: what kinds of verb
frames are attested?EVCA Project• Pick verbs that exist in EVCA
(evca93.index) and also in the PTB
• Produce a report that compares EVCA with what is present in the corpus
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Minimalist Syntax
From stochastic parsing to the (near) latest in syntax• Paper:
– Derivation by Phase (DbP) (Chomsky) – (manuscript 1999, published 2001)
• 4 files on usb drive– Reading Homework over Spring Break– dpb.pdf (the unlocked published version)
you may find the following notes very useful– JU_DbP_1.pdf (DbyP with inline notes from Juan Uriagereka)– JU_DbP_2.pdf (part 2)– Yoon_DbP.pdf (notes from James Yoon, UIUC)
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Software
• Code– GUI: (Tcl/Tk side) treeserver.tcl– GUI: (Prolog side) prolog_client.pl– Grammar: (GUI version) grammar8.pl
• What you need– Tcl/Tk wish
interpreter– Prolog SWI
Prolog– Command line (some) shell
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Processes
• Process #1run treeserver.tcl
under wish interpreter
– example:bash-3.2$ wish treeserver.tclConnection from 127.0.0.1channel closed
• Process #2run SWI-Prolog
– example:bash-3.2$ swiplWelcome to SWI-Prolog (Multi-threaded, 64 bits, Version
5.8.3)
?- [prolog_client, grammar8].% library(error) compiled into error 0.00 sec, 17,480 bytes% library(lists) compiled into lists 0.01 sec, 39,256 bytes% library(shlib) compiled into shlib 0.01 sec, 59,552 bytes% library(unix) compiled into unix 0.01 sec, 65,968 bytes% prolog_client compiled 0.01 sec, 134,368 bytes% grammar8 compiled 0.00 sec, 46,816 bytestrue.
chatter: uses sockets to communicate with Prolog side
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Example 1
• John likes Mary• Run in SWI Prolog window?- parse([john,like,mary]).Probe [v*] agrees with goal
[n mary]Probe [t] agrees with goal
[n john][c[c][t[n john][t[t][v[n john]
[v[v*][V[V like][n mary]]]]]]]
true ;false.
Click to see derivation steps
Tree display zoom slider
Agree(P,G) computationsdisplayedterminal parse output: same
as last step of GUI output
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Current Limitations• John likes Mary• Run in SWI Prolog window?- parse([john,like,mary]).Probe [v*] agrees with goal
[n mary]Probe [t] agrees with goal
[n john][c[c][t[n john][t[t][v[n
john][v[v*][V[V like][n mary]]]]]]]
true ;false.
Implementation limitations:1. No Spell-Out implemented (just
narrow syntax)T + v* f(phi,3-sg-f)+ V(like) = likes
2. No head movement/affix-hopping implemented (part of Spell-Out)input: awarded -> [ed,award]
3. No undo of displacement implemented(displacement is computed from base position)input:[be,ed,award,several,prizes]Several prizes are awarded
Note: not inflected
Spell-Out: implementation of simple inflectional morphology would be straightforwardParsing from final landing sites would require an additional computational mechanism
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Interacting with the Grammar• parse(List).
– Prolog List = input sentence1. Opens a socket connection to
display server2. Calls the definite clause grammar
(DCG) rule for a clause: c(Parse,List,[]).
3. Closes socket connection
• resetDisplay.1. Opens a socket connection to
display server2. Clears the display history for a
derivation3. Closes socket connection
• Components of parse(List) can be called separately– open_connection.– close_connection.– X(Parse,List,[]).
• X = grammar rule name
– useful when other DCG rules need to be called directly
• Implementation (prolog_client.pl)
parse(List) :-open_connection,c(Parse,List,[]),format('~p~n',[Parse]),close_connection.
use after each derivation
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Four Examples
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Example 1• There are likely to be awarded several
prizes• (note input lexme order)?-
parse([be,likely,there,be,ed,award,several,prizes]).
Probe [a!case ed] agrees with goal [n!case several prizes]
Probe [tdef] agrees with goal [n!case several prizes]
Probe [t!phi] agrees with goal [n!phi there]
Probe [t] agrees with goal [n several prizes]
[c[c][t[n there][t[t][v[v be][a[a likely][t[n there][t[tdef][v[v be][a[a ed][V[V award][n several prizes]]]]]]]]]]]
true ;false.
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Example 2• Several prizes are likely to be awarded• (note input lexeme order)?- resetDisplay.true.
?- parse([be,likely,be,ed,award,several,prizes]).
Probe [a!case ed] agrees with goal [n!case several prizes]
Probe [tdef] agrees with goal [n!case several prizes]
Probe [t] agrees with goal [n several prizes][c[c][t[n several prizes][t[t][v[v be][a[a
likely][t[n several prizes][t[tdef][v[v be][a[a ed][V[V award][n several prizes]]]]]]]]]]]
true ;false.
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Example 3• we expect there to be awarded several prizes
(note input lexeme order)
?- parse([we,expect,there,be,ed,award,several,prizes]).
Probe [a!case ed] agrees with goal [n!case several prizes]
Probe [tdef] agrees with goal [n!case several prizes]
Probe [v*!phi] agrees with goal [n!phi there]Probe [v*] agrees with goal [n several prizes]Probe [t] agrees with goal [n we][c[c][t[n we][t[t][v[n we][v[v*][V[V expect]
[t[n there][t[tdef][v[v be][a[a ed][V[V award][n several prizes]]]]]]]]]]]]
true ;false.
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Example 4• we expect several prizes to be awarded
(note input lexeme order)
?- parse([we,expect,be,ed,award,several,prizes]).
Probe [a!case ed] agrees with goal [n!case several prizes]
Probe [tdef] agrees with goal [n!case several prizes]
Probe [v*] agrees with goal [n several prizes]
Probe [t] agrees with goal [n we][c[c][t[n we][t[t][v[n we][v[v*][V[V expect]
[t[n several prizes][t[tdef][v[v be][a[a ed][V[V award][n several prizes]]]]]]]]]]]]
true ;false.
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Basic Computation• start with lexical array of syntactic
objects: {α,..,ω}• Merge “an indispensible operation of a
recursive system”• (external)
– two syntactic objects (SOs): α, β– create merged SO: {α, β}– label({α, β})=label(α) or label(β)
• (internal), implements Displacement– SOs: α and γ, γ properly contained in α – create SO: {α, γ}– label({α, γ})=label(α)
• Agree– active probe SO: α (active =
uninterpretable features), goal SO: β– match and delete uninterpretable features
of probe and goal• Convergent derivation: uninterpretable
features must be eliminated
copy
v*: φ, accN: φ, Case
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Basic Implementation (1)Definite clause grammar (DCG) (simplified)
V([V V N]) --> V(V), n(N).
V([V Verb]) --> [Verb].
features (V) features (N)– phonetic matrix: f(pmatrix,like) f(pmatrix,john)
– (takes an) argument: f(arg,+) f(arg,+)
– uninterpretable Case: f(case,_)
% (big V) verb classesbV(n('V',[],[V,N])) --> bV0(V), n0(N), {theta(V),theta(N)} report 'theta merge V & N'.bV0(n('V',[f(pmatrix,Verb),f(arg,+)],[])) --> [Verb], {transitive(Verb)}.bV0(n('V',[f(pmatrix,Verb),f(arg,+)],[])) --> [Verb], {unaccusative(Verb)}.bV0(n('V',[f(pmatrix,Verb)],[])) --> [Verb], {unergative(Verb)}.
transitive(like). transitive(expect).unergative(run). unaccusative(arrive).
n0(n(n,[f(pmatrix,BNoun)|Fs],[])) --> [BNoun], {bareNoun(BNoun,Fs)}.bareNoun(john,[f(phi,3-sg-m),f(case,_),f(arg,+)]).
variable
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Basic Implementation (2)
Definite clause grammar (DCG) (simplified)v([v N v]) --> n(N), v(v).
v([v v V]) --> v(v), V(V).
v([v*]) --> [].
– features (v*)• uninterpretable φ-features: f(phi,_-_-_)
• can value accusative Case: f(case,acc)
% v*/vPv(n(v,[],[N,V])) --> n0(N), {theta(N)}, v1(V) report 'theta merge N & v'.v1(n(v,[],[V,BV])) --> v0(V), bV(BV), {goals(BV,Goals),agree(V,Goals)} report 'merge v & V'.v0(n('v*',[f(phi,_-_-_),f(case,acc)],[])) --> [].
triggers Agree
f(phi,_-_-_)f(case,acc)
f(phi,3-sg-f)f(case,_)
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Basic Implementation (2)
f(phi,_-_-_)f(case,acc)
f(phi,3-sg-f)f(case,_)
• Agree(v*,N)
Operation: unification (Robinson, 1965)(match and instantiate unvalued features)Probe Goalf(phi,_-_-_) f(phi,3-sg-f)f(case,acc) f(case,_)
Uninterpretable/unvalued features (represented by variables) are eliminated
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Basic Implementation (3)
Definite clause grammar (DCG)T([T N v]) --> n(N), v(v).
T([T N v]) --> v(v), {N a goal}
T([T]) --> [].
– features (φ-complete T)• uninterpretable φ-features: f(phi,_-_-_)
• can value nominative Case: f(case,nom)
• EPP
t(n(t,[],[N,T])) --> n0(N), {nonarg(N)}, t1(T,_) report 'merge expl & T'. % EPP: (1) merget(n(t,[],[Goal,T])) --> t1(T,Goal) report 'move to spec-T’. % EPP: (2) move with maximize matching
t1(n(t,[],[T,V]),G) --> t0(T), v(V), {goals(V,Goals),agree(T,Goals), Goals = [G|_]} report 'merge T & v’.t0(n(t,[f(phi,_-_-_),f(case,nom)],[])) --> [].
triggers Agree
defective Tφ-incompletee.g. infinitivals
╳
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Putting it all together (1)
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Putting it all together (2)
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Putting it all together (3)
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Putting it all together (4)
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Putting it all together (5)
(EPP requirement)
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Putting it all together (6)Operation: Spell-Out (not currently implemented)“John likes Mary”only one copy of John is pronouncedbundleT + v* f(phi,3-sg-f)+ V (like) = likes
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A Worked Example
Consider the derivation of• several prizes are likely to be awarded (= 4(b)(ii))
awarded = award + -ed (adjectival participle)
?- parse([be,likely,be,ed,award,several,prizes]).Probe [a!case ed] agrees with goal [n!case several prizes]Probe [tdef] agrees with goal [n!case several prizes]Probe [t] agrees with goal [n several prizes][c[c][t[n several prizes][t[t][v[v be][a[a likely][t[n several prizes][t[tdef][v[v be][a[a ed][V[V award][n several prizes]]]]]]]]]]]
ϕ-incomplete: uninterpretable Number and Gender onlyuninterpretable Casemorphologically unrealized in English (cf. Icelandic)
-ed
Agree(a,N)-ed: φ, CaseN: φ, Case
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A Worked Example
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A Worked Example
Agree(a,N)-ed: φ, CaseN: φ, Case
Notation: !case means feature is unvalued
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A Worked Example
Agree(Tdef,N)Tdef: φN: φ, Case
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A Worked Example
(several prizes raises to subject position of embedded infinitival)
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A Worked Example
Agree(T,N)T: φ, NominativeN: φ, Case
Case for –ed also valuedbecause of earlier unification stepAgree(a,N)-ed: φ, CaseN: φ, Case
Matrix T
Unification presents an possible advantage: computation is more local
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Probing with multiple goals
(Chomsky 2001)compare with…
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A Worked Example
Spell-OutSeveral prizes are likely to be awarded
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Another Example
?- parse([be,likely,there,be,ed,award,several,prizes]).Probe [a!case ed] agrees with goal [n!case several prizes]Probe [tdef] agrees with goal [n!case several prizes]Probe [t!phi] agrees with goal [n!phi there]Probe [t] agrees with goal [n several prizes][c[c][t[n there][t[t][v[v be][a[a likely][t[n there][t[tdef][v[v be]
[a[a ed][V[V award][n several prizes]]]]]]]]]]]
Consider also the derivation of• There are likely to be awarded several prizes(= 4(b)(i))
pleonastic there: φ-incomplete (Person only)
Agree(a,N)-ed: φ, CaseN: φ, Case
Agree(T,N)T: φN: φ
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Another Example
Agree(a,N)-ed: φ, CaseN: φ, Case
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Examples
(Chomsky 2001)
• Examples (ECM):– (i) we expect there to be awarded several prizes– (ii) we expect several prizes to be awarded
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Example: we expect several prizes to be awarded
Prior Unification: locality advantage
Case
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Example: we expect several prizes to be awarded
Spell-OutWe expect several prizes to be awarded