encoding unl expressions: some problems and proposals igor boguslavsky unl russia [email protected]
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Encoding UNL Expressions: Encoding UNL Expressions: Some Problems and ProposalsSome Problems and Proposals
Igor Boguslavsky
UNL Russia
GeneralsGenerals
UNL: an interlingua or not?No ambiguityUNL vs. natural language
– “at least as powerful as any NL”?– semantics vs. KB
Correct UNL vs. adequate UNL
Adequacy conditionsAdequacy conditions
An adequate UNL expression should:preserve the meaning of the source
text;be convenient for prospective
applications, including deconversion.
Possibility of inverse generation?Possibility of inverse generation?
Necessary but insufficient:invitation of the presidentmod(invitation, president)?
– the president invites somebody– somebody invites the president
Russian: He received the shower (= took the shower)
Tentative procedure Tentative procedure
How to develop a definite and common view on what UNL expressions are adequate?
1. UNL from LCs to UNLC
2. Comments from LCs to UNLC
3. Feedback from UNLC to LCs
4. Update of UNL by LCs
Universal WordsUniversal Words
HeadwordsRestrictionsAttributes
HeadwordsHeadwords
Multi-word UWsSupport verbs
Multi-word UWsMulti-word UWs
They should be avoided, if the their meaning is representable as a combination of meanings of words they are composed of:
UW to be avoided: «Ministery of foreign affairs»
UW to be preferred:mod(ministery.@entry, affair.@pl)
mod(affair.@pl,foreign)
Why so?Why so?
If any free word combination can be made a UW, one can never hope that other partners will have matching UWs in their dictionaries.
Appropriate multi-word UWsAppropriate multi-word UWs
Non-compositional phrases:– «look for(agt>thing,obj>thing)»– «look like(aoj>thing,obj>thing)»
A convenient compromiseA convenient compromise
To account for the fact that a phrase is considered as denoting a single concept, the UNL expression can be enclosed in a scope:
mod:01(ministery.@entry, affair.@pl)
mod:01(affair.@pl,foreign)
Another possibility (Ch. Boitet)Another possibility (Ch. Boitet)
Postulate one UW having the internal structure:«mod(ministery,affair.@pl)_mod(affair.@pl,
foreign)»
Restrictions in UW/KB Restrictions in UW/KB
(1) Semantic function
(2) Knowledge Base function
(3) Argument frame function
(1) Semantic function(1) Semantic function
Restricting the meaning - needed, in particular, to ensure
– disambiguation of the head word – selection of the translation equivalent
(2) KB function(2) KB function
Locating the UW in the KB - needed, in particular, to ensure
– choice of a nearest UW in the case the direct equivalent is absent in the UW dictionary (replacement ability)
– semantic inference
(3) Agrument frame function(3) Agrument frame function
Presenting the argument frame.
Correlation between the semantic Correlation between the semantic and the KB functionsand the KB functions
Semantically- and KB-oriented restrictions do not necessarily coincide:
– semantic restriction: book(icl>thing)
– KB restriction: titmouse{(icl>bird)}
How to selectHow to select semantic semantic restrictionsrestrictionsSeptember{(icl>month>date)} answer(icl>do) (for cases like answer
questions) – answer(icl>be) (for cases like answer expectations) – answer(icl>thing) (for cases like know the answer)
Ru: zhenit’sja – marry(agt>male),
vyxodit’ zamuzh – marry(agt>female).
VERY IMPORTANT!VERY IMPORTANT!
Semantic restrictions should effectively distinguish the meaning we restrict from all other relevant meanings of the same English headword.
They should NOT be equally applicable to more than one meaning.
They should be easily understandable.
ExampleExample
operator - all the meanings denote a thing
WRONG (in the sense ‘inadequate’): – operator(icl>thing)
CORRECT – operator(icl>human)– operator(icl>abstract thing)
Relations useful for Relations useful for disambiguationdisambiguationicliofequ ant (disappeared from the specs?)
– poor(icl>bad): poor quality– ??? poor(icl>having little money)
• “having little money” is a bad UW
– poor(ant>rich): poor people
Needs to be emphasized againNeeds to be emphasized again
UNL News1: build global knowledge– build(agt>thing,obj>thing)
Does not differentiate between different meanings of the headword:– build a railway (a house):
build(agt>thing,obj>concrete thing)– build plans (knowledge):
build(agt>thing,obj>abstract thing)
KB functionKB function
UW: SeptemberMD: September{(icl>month>date)}
What remains unclear-1:What remains unclear-1:
KB semantics. Links between related concepts of different semantic categories are missing. There is no way to express the relationship between “dance” (as a verbal concept) and “dance” (as a nominal concept)), “government” and “governmental”, etc. – dance({icl>do(}agt>person{)}) – dance(icl>action{>event})
What remains unclear-2:What remains unclear-2:
Status of UWs within the restrictions:propose(agt>thing,gol>thing,obj>thing)
– They proposed to the president that a special committee should be set up
«set up» does not fall under «thing». But where then?
What is an argument-1?What is an argument-1?
A is an argument of L --> A is integral to the meaning of L.
What is an argument-2?What is an argument-2?
A is semantically obligatory: L cannot be semantically defined without A being mentioned.
A is not always syntactically obligatory: it can remain unmentioned in a sentence.
Example: Example: buybuy
buy has 4 arguments: a buyer, an object, a seller, the money paid.
All of them are semantically obligatory: “buying” cannot exist without any of them.
None of them is syntactically obligatory:– I bought a book (the seller and the money are not
mentioned).– To buy is more pleasant than to sell (no
arguments are mentioned).
Semantic roles vs. predicate-Semantic roles vs. predicate-argument relationsargument relations UNL does not mark predicate-argument
relations in a systematic way.Assumption: arguments can be reliably
identified based on their semantic role.
It does not work. Why?It does not work. Why?
Too many «difficult» cases. Only a part of semantic relations between the words can be reliably interpreted in terms of semantic roles.
Too many mismatches. Assignment of semantic roles cannot be done in a consistent way (especially in the UNL multi-lingual and multi-cultural environment).
The reason:The reason:
Numerous mismatches in the representation of the same or similar phenomena are rooted in the fundamental impossibility of a consistent interpretation of ALL argument relations in terms of a fixed SMALL number of semantic roles.
ExamplesExamples
Nothing (obj) prevents the members (ben) from discussing (gol) this problem– why beneficiary (ben)?– why finite state (gol)?
protect nature from pollution (?) familiarize students with India (?)
Difference between arguments Difference between arguments and non-arguments-1and non-arguments-1Any nominal concept can have a
purpose, e.g. – a stone for driving nails
Therefore {pur>uw} is assigned to UW «thing» and is inherited by all UWs lying below.
Difference between arguments Difference between arguments and non-arguments-2and non-arguments-2Purpose is NOT an argument of “stone”:
a stone has no obligatory conceptual link with the purpose.
Purpose IS an argument of “method”: a method cannot exist without a purpose.– a method for calculating taxes
Another example: Another example: borrowborrow
– X borrows Y from Z for W = • Z owns Y, • X makes Z to give him Y,• X promises Z to give Y back after W
expires
– borrow cannot exist without 4 participants: agent, object, source, duration
Difference between arguments Difference between arguments and non-arguments-3and non-arguments-3Each action has a certain duration.
Therefore {dur>time} is assigned to UW «do» and is inherited by all UWs lying below.
Besides this, borrow has a semantic argument with the role ‘duration’
Argument vs. non-argumentArgument vs. non-argument
(1) John borrowed money for 3 years– Argument W: term of the loan. John
promised to return money after 3 years
(2) John has been borrowing money for 3 years– Non-argument: the situation ‘John is
borrowing money’ lasted for three years (the term of each loan is not specified)
Why important? - For semantic Why important? - For semantic processingprocessing(1) can answer the question on the terms of
the loan - (2) cannot do so.mod(invitation, president)
– the president invites somebody (arg. 1)– somebody invites the president (arg. 2)– the invitation has an unspecified connection with
the president (non-arg.)NB: the specs do not allow to draw this
distinction!
Why important? - For Why important? - For deconversiondeconversionThe arguments and non-arguments are
very often encoded differently:– dur: Ru «borrow on 3 years» vs. during 3
years – rsn: afraid of darkness, tremble with fear not:
*afraid because of darkness – scn: In [scn] this country the relations
between the nations are based on [scn-arg] mutual respect
How to differentiate?How to differentiate?
The distinction between the arguments and the non-arguments should be drawn both in the UWs and in UNL expressions.
Proposal for UWsProposal for UWs
Restrictions corresponding to arguments should be systematically and exhaustingly represented in KB.
They can either be included into the UW, or be inherited from upper concepts.
Proposal for UWsProposal for UWs
They should be formally opposed to non-argument restrictions.
One of the ways: capitalization. – thing{(and>thing,…,pur>uw,…)} – method(icl>abstract thing,Pur>uw) – do{and>do,…,dur>period,…)}– borrow(icl>do,…Dur>period)
Another possibility: – dur vs. dur.@A
Proposal for UNL expressionsProposal for UNL expressions
Mark argument relations (Ch. Boitet): – @A, @B, @C…
relation for (1):– dur.@A(borrow, year)
relation for (2):– dur(borrow, year)
Sample UW dictionary entrySample UW dictionary entry
Current UW: responsible(aoj>thing,obj>thing)
It is proposed to introduce a comment:
responsible (Aoj>thing,Obj>thing,Gol>*);he (aoj) is responsible to me (gol) for his
actions (obj) (example)
;IB_Ru, 29/11/02 (author and date)
Comments in MDComments in MD
Not only for illustrating argument frames, but also for clarifying concepts.
Specs modification is needed.
AttributesAttributes
Dictionary of attributes (explanation of the attribute, examples)
Procedure for introduction new attributes should be set up.
Issues concerning KBIssues concerning KB
Adjectival concepts
Adjectival concepts: mod vs. aojAdjectival concepts: mod vs. aoj
Two major classes of adjectives: – (aoj>thing) vs. (mod<thing)
Specs: “For an adjectival concept, (aoj>thing) or (mod<thing) should be attached to the Basic UW. (aoj>thing) is for expressing a predicative concept, whereas (mod<thing) is for expressing restrictive concept”.
We should distinguish between:We should distinguish between:
(a) a syntactic property: whether the adjective is used predicatively (Greeks are wise) or attributively (the wise Greeks);
(b) a semantic property: what does the adjective mean when used attributively:– restriction;– qualification.
Only (b) should interest us.
Restrictive vs. non-restrictive Restrictive vs. non-restrictive
Wise Greeks diluted wine with water– restrictive: Those Greeks who were wise
diluted wine with water. Silly ones didn’t.– non-restrictive (qualificative): Greeks were
wise. They diluted wine with water. Non-attributive (predicative) adjective
does not restrict the noun:– Greeks are wise.
AdjectivesAdjectives
Some adjectives can only be restrictive:– Many dogs have curly hair
Some adjectives can only be non-restrictive:– Get those damned dogs out of the room! – Dear colleagues!
Most of the adjectives can be both restrictive and non-restrictive.
Non-adjectivesNon-adjectives
The old people in the street were very tired.– Those who were in the street were tired;
others were not tired.– The old people were very tired. They were
in the street.There is no UW to which a restriction
can be assigned!
What is more…What is more…
In some languages restricive vs. non-restrictive interpretations of relative clauses are marked by punctuation (English, Spanish).
RestrictiveRestrictive
No commas are allowed:
– The old people who came a long way were tired.
– Los viejos que habían venido de muy lejos estaban cansados.
Non-restrictiveNon-restrictive
Commas are needed:
– The old people, who came a long way, were tired.
– Los viejos, que habían venido de muy lejos, estaban cansados.
ProposalProposal
Renounce from the division of adjectives into (aoj>*) and (mod<*).
In order to account for this difference, introduce two attributes (@restr, @non-restr) which can be added to any modifier (an adjective, a prepositional phrase, a clause), if the author wishes to mark the restrictive or non-restrictive interpretation.
Why attributes are better than Why attributes are better than restrictions?restrictions?Attributes reflect the point of view of the
speaker in the current situation and not the permanent property of the word.
Attributes are optional and may be not assigned, if the author does not wish to specify his point of view.
The strongest argumentThe strongest argument
The restrictive vs. non-restrictive opposition is relevant not only for adjectives but also for other types of noun modifiers.
These modifiers cannot be assigned restrictions but can easily take an attribute.