Week3 Conceptual Dependency

Artificial Intelligence – CS364Artificial Intelligence – CS364Knowledge RepresentationKnowledge Representation

Lectures on Artificial Intelligence – CS364Lectures on Artificial Intelligence – CS364

Conceptual DependencyConceptual Dependency

20th September 2005

Dr Bogdan L. Vrusiasb.vrusias@surrey.ac.uk

ContentsContents• Definition of Conceptual Dependency Grammar

• Building blocks

• Advantages and disadvantages

• Exercises

Concepts and RepresentationConcepts and Representation• A number of authors in AI have addressed the question of

the 'concept'-based organisation of knowledge and we use two examples to illustrate this:

– Firstly, we consider a verb-oriented organisation of knowledge proposed by Schank: Conceptual Dependency Grammar.

– Then we go on to discuss a highly nominalised system proposed by Sowa: Conceptual Graphs.

Conceptual DependencyConceptual Dependency• Conceptual dependency (or CD) is a theory of how to

represent the meaning of natural language sentences in a way that:

– First, facilitates for drawing inferences from the sentences.

– Second, the representation (CD) is independent of the language in which the sentences were originally stated.

Conceptual Dependency TheoryConceptual Dependency Theory• Schank's (1975) Conceptual Dependency Theory was developed as

part of a natural language comprehension project.

• Schank's claim was that sentences can be translated into basic concepts expressed as a small set of semantic primitives.

• Conceptual dependency allows these primitives, which signify meanings, to be combined to represent more complex meanings.

• Schank calls the meaning propositions underlying language "conceptualisations".

Conceptual Dependency TheoryConceptual Dependency Theory• Schank’s project is the ‘representation of meaning in an

unambiguous language-free manner’ (1973:187).

• ‘Any two utterances that can be said to mean the same thing, whether they are in the same or different languages, should be characterised in only one way by the conceptual structure’ (1973:191)

• Towards a representation ‘in terms that are as interlingual and as neutral as possible’ (ibid.)

CD Building BlocksCD Building Blocks• CD theorists argue that

– "the CD representation of a sentence is built not out of primitives corresponding to the words used in the sentence, but rather out of conceptual primitives that can be combined to form the meanings of words in any particular language"

• Building Blocks– Primitive conceptualizations (conceptual categories)

– Conceptual dependencies (diagrammatic conventions)

– Conceptual cases

– Primitive acts

– Conceptual tenses

Primitive ConceptualizationsPrimitive Conceptualizations• Schank emphasises analysis of a sentence/utterance at the

conceptual level or to analyse conceptualisation.

• Conceptual dependency theory of four primitive conceptualizations:

– actions (ACT: actions)

– objects (PP: picture producers)

– modifiers of actions (AA: action aiders)

– modifiers of objects (PA picture aiders)

Concept can beConcept can be• An abstract or concrete object that invokes an image

– "cars" are concrete objects– "gravity" is an abstract concept

• An object (nominal) produces a picture (PP)

• Something an animate object does.– "running" is an action

• A modifier that modifies an object or an action.• A modifier that specifies an action or a nominal.

– "blue" is a PA modifier (e.g. A blue car)– "quickly" is a AA modifier (e.g. He quickly run)

Conceptual DependenciesConceptual Dependencies• Conceptual categories (PP, ACT, PA and AA) relate to each other in

specified ways. These relations are called dependencies by Schank.

• In a dependency relation, one partner or item is dependent and the other dominant or governing.

• A governor dependent is a partially ordered relationship– A dependent must have a governor and is understood in terms of the

governor– A governor may or may not have dependent(s) and has an independent

existence– A governor can be a dependent

• PP and ACT are inherently governing categories.• PA and AA are inherently dependent.

Conceptual DependenciesConceptual Dependencies• For a conceptualisation to exist, there must be at least two

governors:– E.g. Sally stroked her fat cat

PP: Sally, cat, her [Sally]

ACT: stroke

PA: fat

Governors: Sally, stroke, cat

Dependent: PP (cat) on ACT (stroke)

PA (fat) on PP (cat)

PP (cat) on PP (her[Sally])

Building CD graphsBuilding CD graphs• E.g. Sally stroked her fat cat

– Sally and stroking are necessary for conceptualisation: there is a two-way dependency between each other:

Sally stroke

– Sally’s cat cannot be conceptualised without the ACT stroke it has an objective dependency on stroke

Sally stroke cat. O

Building CD graphsBuilding CD graphs• E.g. Sally stroked her fat cat

– The concept ‘cat’ is the governor for the modifier ‘fat’:

Sally stroke cat fat

– The concept PP(cat) is also governed by the concept PP(Sally) through a prepositional dependency:

Sally stroke cat POSS-BY

fat Sally[her]

Conceptual CasesConceptual Cases• Dependents that are required by an ACT are called Conceptual

Cases:

• There are four main conceptual cases:

– Objective Case (O)

– Recipient Case (R)

– Instrumental Case (I)

– Directive Case Relation (D)

Conceptual CasesConceptual Cases– Objective Case (O): "John took the book"

oPP [John] PP [book]o

ACT [took]

Conceptual CasesConceptual Cases– Recipient Case (R): "John took the book from Mary"

PP [John]

PP [book]

PP [Mary]

ACT [took]

Conceptual CasesConceptual Cases– Instrumental Case (I): "John ate the ice cream with a spoon"

IPP [John]

PP [John]

ACT [eat]

PP [ice cream]

PP [spoon]

ACT [do]

Conceptual CasesConceptual Cases– Directive Case Relation (D) "John drove his car to London from

Guildford"

PP [John] ACT [do]

ACT [drove]PP [car]

PP [London]

PP [Guildford]

POSS-BY

PP [John]

Prepositional DependencyPrepositional DependencyConsider the following sentences:

Possessione.g. "This is Sally’s cat": Cat

POSS-BY Sally

Locatione.g. "Sally is in London": London

LOCSally

Containmente.g. "The glass contains water": Water

CONTGlass

Primitive ACTsPrimitive ACTsPrimitive Act Elaboration

ATRANS Transfer of an abstract relationship such as possession ownership or control (give)

PTRANS Transfer of the physical location of an object (go)

PROPEL Application of a physical force to an object (push)

MOVE Movement of a body part of an animal by that animal (kick)

GRASP Grasping of an object by an actor (grasp)

INGEST Taking in of an object by an animal to the inside of that animal (eat)

EXPEL Expulsion of an object from the object of an animal into the physical world (cry)

MTRANS Transfer of mental information between animals or within an animal (tell)

MBUILD Construction by an animal of new information of old information (decide)

CONC Conceptualise or think about an idea (think)

SPEAK Actions of producing sounds (say)

ATTEND Action of attending or focusing a sense organ towards a stimulus (listen)

Primitive ACTsPrimitive ACTse.g. I gave a book to Sally

PP [I]

PP [Sally]

PP [book]

PP [I]o

RACT [gave]

RATRANS

Conceptual TensesConceptual Tenses• Any conceptualisation can be modified as a whole by a

conceptual tense.

• John took the book (John took) can be denoted by looking at the lemma take (from which the past tense took was derived):

John ATRANSp

Conceptual TensesConceptual Tenses

Symbol Elaborationp Past

f Future

t Transition

ts Start Transition

tf Finished Transition

k Continuing

? Interrogative

/ Negative

nil Present

delta Timeless

c Conditional

"John will be taking the book":

"John is taking the book":

John taking

John ATRANSk

John taking

John ATRANSf

Summarising CD Building BlocksSummarising CD Building BlocksE.g. I took a book from Sally

• Primitive conceptualizations (conceptual categories):– Objects (Picture Producers: PP): Sally, I, book

• Conceptual dependencies (diagrammatic conventions):– Arrows indicate the direction of dependency– Double arrow indicates two way link between actor and action

• Conceptual cases:– "O" indicates object case relation– "R" indicates recipient case relation

• Primitive acts:– ATRANS indicates transfer (of possession)

• Conceptual tenses:– "p" indicates that the action was performed in the past

Sallyo

RATRANS

Semantic Nets Vs CDSemantic Nets Vs CD• Semantic Nets only provide a structure into which nodes

representing information can be placed.

• Conceptual Dependency representation, on the other hand, provides both a structure and a specific set of primitives out of which representations of particular pieces of information can be constructed.

Advantages of CDAdvantages of CD• The organisation of knowledge in terms of the primitives

(or 'primitive acts') leads to a fewer inference rules.

• Many inferences are already contained in the representation itself.

• The initial structure that is built to represent the information contained in one sentence will have holes in it that have to be filled in:– holes which will serve as attention focusers for subsequent

sentences.

Disadvantages of CDDisadvantages of CD• CD requires all knowledge to be broken down into 12 primitives:

sometimes inefficient and sometimes impossible.

• CD is essentially a theory of the representation of events: though it is possible to have an event-centred view of knowledge but not a practical proposition for storing and retrieving knowledge.

• May be difficult or impossible to design a program that will reduce sentences to canonical form. (Probably not possible for monoids, which are simpler than natural language).

• Computationally expensive to reduce all sentences to the 12 primitives.

ExercisesExercises• Please create the conceptual dependency representation of

the following sentences:– John ran

– John is a Doctor

– John’s Dog

– John pushed the cart

– Bill shot Bob

– John ate the egg

– John prevented Mary from giving a book to Bill

Solution 1Solution 1• "John ran" (Schank and Colby 1973)

John PTRANSp

Solution 2Solution 2• "John is a doctor" (Schank and Colby 1973)

John doctor

Solution 3Solution 3• "John’s Dog" (Schank and Colby 1973)

POSS-BY

Solution 4Solution 4• "John pushed the cart" (Schank and Colby 1973)

oJohn carto

PROPELp

Solution 5Solution 5• "Bill shot Bob" (Schank and Colby 1973)

RBill bulleto

PROPELp

health(-10)

Solution 6Solution 6• "John ate the egg" (Schank and Rieger 1974).

INSIDE

John eggoINGEST

Solution 7Solution 7• "John prevented Mary from giving a book to Bill" (Schank

and Rieger 1974).

pJohn DO

ATRANS

ClosingClosing

• Questions???

• Remarks???

• Comments!!!

• Evaluation!

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