unification grammar
TRANSCRIPT
Unification Grammar
Trying to solve the same problems
Phrase structure rules
Transformational Grammar has PSRs
But it also needs features
And features may move
Or be copied
Transformational Grammars ALSO need MOVEMENT
PSRs, features, and movement
Unification Grammars
No movement
Phrase Structure Rules -- yes
Movement -- no
Just structure-sharing
Structure-sharing MEANS unification
And VERY complicated information IN words!
Attribute-value matrix
Head-driven Phrase Structure Grammar
HPSG
HPSG is the most popular Unification Grammar
Attribute-value matrix (AVM)
AVMs MODEL words
This is a model of a word
Very complex and structured
Words have ATTRIBUTES
For example PHON
PHON is phonological or sound-related information
Nobody cares about PHON
Unless they’re PHONologists!
SYNSEM is an attribute
SYNSEM is the syntactic and semantic information
We DO care about SYNSEM
LOCAL is an attribute
Forget about it for now
CATEGORY or CAT
CAT carries the syntactic features
What kind of word is it?
[She] is a noun
HEAD attribute is noun
Nominative CASE
CONTENT and CONTEXT is the semantic info
[She] is 3rd person
[She] is singular
[She] is feminine
[She] CONTENT
• PER 3rd
• NUM sing• GEND fem
HEAD attribute is verb
[walks][walks]
[walks] has VALENCE attributes
[walks][walks]
VALENCE is also known as SUBCAT
[walks][walks]
VALENCE/SUBCAT who cares?
[walks][walks]
VALENCE sounds more scientific
[walks][walks]
VALENCE means attract or repel
[walks][walks]
[walks] attracts a noun
[walks][walks]
[walks] attracts a subject
[walks][walks]
[walks] specifies information about the subject
[walks][walks]
[walks]
SUBJ<CAT|HEAD noun|CASE nominative CONT [1]|PER 3rd
NUM singGEND –
CONT|walker [1]
CONT of subject matches in CONT of the verb
SUBJ<CAT|HEAD noun|CASE nominative CONT [1]|PER 3rd
NUM singGEND –
CONT|walker [1]
If the verb takes [she] as a subject …
SUBJ<CAT|HEAD noun|CASE nominative CONT [1]|PER 3rd
NUM singGEND –
CONT|walker [1]
CONT [1] matches CONT of [she]
SUBJ<CAT|HEAD noun|CASE nominative CONT [1]|PER 3rd
NUM singGEND –
CONT|walker [1]
If the verb takes [she] as a subject
SUBJ<CAT|HEAD noun|CASE nominative CONT [1]|PER 3rd
NUM singGEND –
CONT|walker [1]
[She] CONTENT
• PER 3rd
• NUM sing• GEND fem
[She] CONTENT
• PER 3rd
• NUM sing• GEND fem
So when [walks] takes [she] …
SUBJ<CAT|HEAD noun|CASE nominative CONT [1]|PER 3rd
NUM singGEND –
CONT|walker [1]
This …
SUBJ<CAT|HEAD noun|CASE nominative CONT [1]|PER 3rd
NUM singGEND –
CONT|walker [1]
… becomes this
SUBJ<CAT|HEAD noun|CASE nominative CONT [1]|PER 3rd
NUM singGEND fem
CONT|walker [1]
[walks] VALENCE features and CONT features
Notice the structure-sharing
Usually marked with a number in a square
Why is it a number in a square?
Why not?
Who cares?
Could be a color
Or a funny shape – it doesn’t matter
The number in the square shows the structure-sharing
It shows the UNIFICATION
That’s it!
STRUCTURE A = [m _ t _ h]STRUCTURE B = [_ a _ c _]
Unify A and BWhat happens?A+B = [match]That’s it!
It looks complicated
STRUCTURE A = [s _ a _ e]STRUCTURE B = [_ h _ r _]
Unify A and BWhat happens?A+B = [share]But it’s basically very simple (and no movement)
Here’s some [walks] info again!
Notice the VALENCE specifications
[Walks] attracts a NP with nominative case
Walks attracts a NP with CONT [3rd,sing]
[she] has CASE nom
[she] has CONT 3rd, sing, fem
No problem
• She walks • That’s a good sentence
• What about this?• Her walks• Is that a good sentence?• No• Why?
Here’s [her]
[walks] attracts a NP[nom]
[her] is CASE acc (accusative)
The CONT of [her] is OK
But it is the wrong syntactic CATEGORY
Unification fails …
… if there is a mismatch
So don’t panic …
[walks][walks]
… when you see these complicated AVMs
[walks][walks]
It takes a bit of time …
[walks][walks]
You have to get used to it
[walks][walks]
But it’s basically very simple
[walks][walks]
And no movement
[walks][walks]
Don’T forget -- VALENCE features
[walks][walks]
VALENCE or SUBCAT
[walks][walks]
[walks] attracts a noun
[walks][walks]