Embedded Clauses in TAG

Embedded Clauses

We think that they have left.

COMP NP VP

S

V S-bar

NP VP

S

Embedded Clause

Matrix Clause

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

It seems that they have left.

COMP NP VP

S

V S-bar

NP VP

S

They seem to have left.

COMP

VP

V VP-bar

NP VP

S

They seem to have left.

COMP

VP

V VP-bar

NP VP

S

They seem e to have left.

NP VP

V S

NP VP

S

Two ways to represent that “seem” and “leave” share a subject.

Subj theyVerb seemComplement 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.

They try to leave.

COMP

VP

V VP-bar

NP VP

S

They(i) try PRO(i) to leave.

NP VP

V S

NP VP

S

Two ways to represent that “try” and “leave” share a subject.

Subj theyVerb seemComplement subj verb leave

PRO is an empty string, but not the same kind of empty string as e

Coindexing indicates that PRO refers to “they”.

“Seem” type verbs in TAG

S

John to be happy

V AP

NP VP V VP

VP

seem

Initial Tree

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”.

Adjunction site

S

NP VP

to be happy

V AP

VP

John

V VP

VP

seem

Adjunction site

to be happy

V AP

VP

S

NP VP

John

V VP

VP

seem

Adjunction

V VP

VP

seems

to be happy

V AP

S

NP

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

V S

NP VP

John tried

S

NP VP

TO VP

PRO leave

Adjunction site

These trees show the number of arguments for each verb:

“Try” has two arguments.

“Leave” has one argument.

Initial Tree

Auxiliary Tree

S

NP VP

TO VP

PRO leave

SAdjunction site

S

V S

NP VP

John tried

S

NP VP

TO VP

PRO leave

SAdjunction site

S

V S

NP VP

John tried

S

NP VP

TO VP

PRO leave

S

V

NP VP

John tried

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?