Transcript Embedded Clauses in TAG

Embedded Clauses in TAG
Embedded Clauses
Matrix Clause
S
NP
VP
V
S-bar
Embedded Clause
S
COMP
We think that
NP
VP
they have left.
Linguistic Background
• Constraints
• Semantic roles
Embedded Clauses:
Constraints
• Main verbs are subcategorized for
– The complementizer (that, for, to, etc.) Nonfinite for-to
– We hoped for there to be no trouble.
• A word at the beginning of a subordinate clause that
identifies it as a complement
– The morphology of the embedded verb
• Finite: present or past tense
• Non-finite: infinitive, present participle, past
participle
Examples: Constraints imposed by the
main verb on the embedded verb
• “Say” requires a finite embedded clause:
– Sam said that Sue saw him.
– *Sam said Sue to see him.
– *Sam said that Sue seeing him.
• “that” is a complementizer that goes with finite
clauses. When it comes after a verb, it is
optional:
– Sam said Sue saw him.
– That he left is a problem.
– *He left is a problem.
• “That” is only optional after a verb.
Examples: Constraints imposed by the
main verb on the embedded verb
• “Expect” takes a finite clause or an infinitive, but
not a participle:
– We expect to see him.
– We expect that we will see him.
• Modal auxiliary verbs (will, would, may, might, can, could,
shall, should, etc) are always finite.
– *We expect seeing him.
• Might sound grammatical because “seeing him” can be a
noun phrase, and “expect” can occur with a noun phrase:
“We expect problems”
– *We expect seen him.
Finite embedded clauses
• Finite embedded clause
– I believe (that) it is snowing.
– Say, think, scream
• Finite with dummy subject
– It seems that they have left.
• Finite embedded question
– I wondered/asked whether/if it was snowing.
• Finite plus object
– We told them that it was snowing.
• Finite plus PP
– We said to them that it was snowing.
Non-finite embedded clauses
• Non-finite for-to
– We hoped for there to be no trouble.
• Non-finite: Raising to subject
– They seem (to us) to have left.
– Appear, continue
• Non-finite: Subject Equi
– They tried to leave.
– Intend, expect, plan, hope
• Non-finite: Raising to object
– We believe them to have left.
– consider
• Non-finite: Object Equi
– We persuaded them to leave.
– Convince, order, force, signaled
• Non-finite: promise
– We promised them to leave.
English Auxiliary Verbs
• Modal verbs: (will, would, can, could, shall, should, may,
might, and a few others)
– Invariant: don’t have a third person singular form.
– Only occur where you can have present or past tense. Don’t
occur in infinitives, gerunds, or participles:
•
•
•
•
I will go.
I would go.
I said I would go.
*I want to can go.
– Compare: I want to be able to go.
• *Canning go would make me happy.
– Compare: Being able to go would make me happy.
– The next verb must be an infinitive without “to”.
• I will have gone.
• I will be going.
• *I will going/gone/went/goes.
English Auxiliary Verbs
• “Have”
– Must be followed by a past participle:
• I have gone.
• *I have going/went/goes/go.
• Progressive “be”
– Must be followed by a present participle:
• I am going.
• *I am goes/went/go.
• Passive “be”
– Must be followed by a passive verb:
• The cookies were devoured.
• *The cookies were devouring/devours/devour.
Auxiliary verbs as main verbs
(for syntax; not for semantics)
• The auxiliary verb can impose constraints on the
main verb.
– Sam is sleeping/*slept/*sleeps.
• The main clause has to be finite (has a tense).
– Sam sleeps/slept.
– *Sam to sleep.
– *Sam sleeping.
• The auxiliary verb carries the tense, not the main
verb:
– Sam is sleeping.
– *Sam be sleeps.
S
NP
VP
V
Sam
VP
is
sleeping
S
NP
Sam
VP
V
VP
has
slept
Summary of constraints on
embedded clauses
• The main verb determines the tense and
morphology of the embedded verb.
• More than one embedded clause:
– Each verb determines the tense and
morphology of the next one:
• I think that Sam tried to sleep.
• “Think” requires “try” to be finite.
• “Try” requires “sleep” to be infinitive.
The car needs washed.
• In most dialects of English, “need” takes an infinitive as a
complement:
– The car needs to be washed.
– Sam needs to sleep.
• There are a few verbs that take passive participles as
complements:
–
–
–
–
We had them arrested by the police.
We got them arrested by the police.
They were arrested by the police.
They got arrested by the police.
• In Pittsburgh, “need” and “want” can take passive
participles as complements:
– The car needs washed.
– Do you want pushed?
Semantic Roles
• Syntax
– Word order
– Constituent structure
– Constraints: agreement, subcategorization,
case marking
– Semantic roles:
• Sue interviewed Sam.
• Sue is the interviewer.
• Sam is the interviewee.
Semantic Roles in Embedded
Clauses
• Sam tried to sleep.
– Sam is the agent of “try”
– Sam is the agent of “sleep”
– “Sam to sleep” is what was tried.
• Sam seemed to sleep.
– Sam is the agent of “sleep.”
– Sam is not an argument of “seem.”
– “Sam to sleep” is the only argument of
“seem”.
Just the facts
• How many semantic arguments does each
verb take:
– “Try” takes two.
– “Seem” takes one.
• Do the main clause and the embedded
clause share a subject?
– Yes. Both “seem” and “try” share their
subjects with the embedded verb.
How we know that the semantic role
assignments are different with Seem and Try
• The cat seems to be out
of the bag.
• There seems to be a
problem.
• That seems to be my
husband.
• The doctor seemed to
examine Sam.
• Sam seemed to be
examined by the doctor.
• The cat tried to be out of
the bag.
• *There tried to be a
problem.
• That tried to be my
husband.
• The doctor tried to
examine Sam.
• Sam tried to be examined
by the doctor.
Raising to subject
S
NP
S
VP
V
NP
S-bar
VP
V
VP-bar
S
COMP
It
seems that
NP
VP
VP
COMP
they have left. They seem to
have left.
S
NP
VP
V
VP-bar
Two ways to represent that
“seem” and “leave” share a
subject.
VP
COMP
They seem to
have left.
S
NP
VP
V
S
NP
They seem e
VP
to have left.
Subj
Verb
Complement
they
seem
subj
verb leave
Comparison
• Second method:
– Allow empty strings as terminal nodes in the tree.
– An empty string needs to take the place of the missing subject of the
lower clause.
– The empty string is linked to the subject of the main clause to show that
the main and embedded clauses share a subject.
– The tree represents: word order, constituent structure, grammatical
relations, semantic roles.
• First method:
– No empty strings in the tree.
– The tree represents only word order and constituent structure.
– Grammatical relations and semantic roles are represented in a separate
structure.
– Structure sharing in the representation of grammatical relations shows
that the two verbs share a subject.
• Is one method simpler than the other?
– No. Both methods have to represent word order, semantic relations,
grammatical relations, and semantic roles.
• People who argue that one is simpler are usually wrong – they don’t know
how to count steps in a derivation.
Two ways to represent that
“try” and “leave” share a
subject.
S
NP
VP
V
VP-bar
Subj
Verb
Complement
VP
COMP
They try to
they
seem
subj
verb leave
leave.
S
NP
PRO is an empty string, but not the same kind
of empty string as e 
VP
V
S
Coindexing indicates that PRO refers to “they”.
NP
They(i) try
VP
PRO(i) to leave.
“Seem” type verbs in TAG
VP
S
NP
VP
V
John
Adjunction site
AP
to be happy
Initial Tree
V
VP
seem
Auxiliary Tree
These trees represent the number of
arguments for each verb:
“Seem” has one argument, represented
as a VP.
“To be happy” has one argument, “John”.
S
NP
VP
V
AP
to be happy
John
VP
Adjunction site
V
seem
VP
S
NP
S
NP
V
VP VP
V
VP
seems V
Adjunction
VP
seem
AP
to be happy
VP
V
AP
to be happy
John
VP
John
This tree shows word order and
constituent structure.
It also shows that “John” is the
subject of “seem.”
It doesn’t show that “John” is the
subject of “to be happy.”
“Try” type verbs in TAG
S
S
NP
NP
VP
V
John
VP
TO
S
PRO
tried
Auxiliary Tree
Adjunction site
VP
leave
Initial Tree
These trees show the number of arguments for
each verb:
“Try” has two arguments.
“Leave” has one argument.
S
NP
VP
V
John
tried
S
S
NP
Adjunction site
VP
TO
PRO
VP
leave
Adjunction is only
allowed at the top S
node so as not to mess
up compositional
semantics:
After you put together
“try to leave” you don’t
want to have to take it
apart again by inserting
another verb like
“expected” as in:
John tried to expect to
leave.
Inserting “seem” into the
middle of the tree
doesn’t require you to
disassemble any of the
semantic pieces that
were already
assembled?
S
NP
VP
V
John
S
triedNP
VP
TO
PRO
VP
leave