What Is the

1
What Is the Context forContextual Vocabulary
Acquisition?

• William J. Rapaport
• Department of Computer Science Engineering
• Department of Philosophy
• Center for Cognitive Science
• NSF ROLE Grant REC-0106338

2
Outline

• People can figure out a meaning for a word from
  context
• What does context mean in this context?

3
Definition of CVA

• Contextual Vocabulary Acquisition def
• the acquisition of word meanings from text
• incidental
• deliberate
• by reasoning about
• contextual cues
• background knowledge
• Including prior word-meaning hypotheses, language
  knowledge
• without external sources of help
• no dictionaries
• no people

4
CVA From Algorithm to Curriculum

• Computational theory of CVA
• Based on
• algorithms developed by Karen Ehrlich (1995)
• verbal protocols (case studies)
• Implemented in a semantic-network-based
• knowledge-representation reasoning system
• SNePS (Stuart C. Shapiro colleagues)
• Educational curriculum to teach CVA
• Based on our algorithms protocols
• To improve vocabulary reading comprehension
• Joint work with Michael Kibby
• Center for Literacy Reading
  Instruction

5
People Do Incidental CVA

• We know more words than explicitly taught
• Average high-school grad knows 45K words
• ? learned 2.5K words/year (over 18 yrs.)
• But only taught 400/school-year
• 4800 in 12 years of school ( 10 of total)
• ? Most word meanings learned from context
• incidentally (unconsciously)
• How?

6
People Also Do Deliberate CVA

• Youre reading
• You understand everything you read, until
• You come across a new word
• Not in dictionary
• No one to ask
• So, you try to figure out its meaning from
  context
• How?
• guess? derive? infer? deduce? educe? construct?
  predict?
• our answer Compute it! Via inferential search
  of context/KB
• But what KB?

7
CVA as Cognitive Science

• Studied in
• AI / computational linguistics
• Psychology
• Child-language development (L1 acquisition)
• L2 acquisition (e.g., ESL)
• Reading education (vocabulary development)
• Thus far multi-disciplinary
• Not yet inter-disciplinary!

8
What does brachet mean?

9
(From Malorys 15th century Morte dArthur page
in brackets)

• There came a white hart running into the hall
  with a white brachet next to him, and thirty
  couples of black hounds came running after them.
  66
• People brachet animal? inanimate object?
  dont know.
• Computer brachet physical object
• (because only physical objects have color)
• As the hart went by the sideboard, the white
  brachet bit him. 66
• People brachet animal
• Computer brachet animal
• (because only animals bite)

10
Malory, continued

• 3. The knight arose, took up the brachet and
  rode away with the brachet. 66
• People brachet animal / small animal
• Computer brachet small animal
• (because picked up and carried)
• 4. A lady came in and cried aloud to King
  Arthur, Sire, the brachet is mine. 66
• People brachet pet / small, valuable animal
• Computer brachet small, valuable animal
• (because whats wanted is valuable)

11
Malory, continued

• There was the white brachet which bayed at him
  fast. 72
• People brachet dog
• Computer brachet hound (i.e., dog that hunts)
• (because only hounds, which are hunting dogs,
  bay)
• The hart lay dead a brachet was biting on his
  throat, and other hounds came behind. 86
• People brachet hound
• Computer brachet hound (i.e., dog that hunts)
• (because x and other y ? x is a y)

12
How (Not) to Teach CVAVague Strategies

• Clarke Nation 1980 a strategy (algorithm)
• Look at word context determine POS
• Look at grammatical context
• E.g., who does what to whom?
• Look at wider context
• E.g., for clues re causal, temporal,
  class-membership, etc.
• Guess the word check your guess

13
Vague strategies

• guess the word
• then a miracle occurs
• Surely,
• we computer scientists
• can be more explicit!

14
A More Precise, Teachable Algorithm

• Treat guess as a procedure call
• Fill in the details with our algorithm
• Convert the algorithm into a curriculum
• To enhance students abilities to use deliberate
• CVA strategies

15
Figure out meaning of word from what?

• context (i.e., the text)?
• Werner Kaplan 52, McKeown 85, Schatz Baldwin
  86
• context and readers background knowledge?
• Granger 77, Sternberg 83, Hastings 94
• context including background knowledge?
• Nation Coady 88, Graesser Bower 90
• Note
• context text ? context is external to
  readers mind
• Could also be spoken/visual/situative (still
  external)
• background knowledge internal to readers
  mind
• What is (or should be) the context for CVA?

16
Some Proposed Preliminary Definitions(to extract
order out of confusion)

• Unknown word for a reader def
• Word or phrase that reader has never seen before
• Or only has vague idea of its meaning
• Different levels of knowing meaning of word
• Notation X

17
Proposed preliminary definitions

• Text def
• (written) passage
• containing X
• single phrase or sentence several paragraphs

18
Proposed preliminary definitions

• Co-text of X in some text def
• The entire text minus X i.e., entire text
  surrounding X
• E.g., if X brachet, and text
• There came a white hart running into the hall
  with a white brachet next to him, and thirty
  couples of black hounds came running after them.
• Then Xs co-text in this text
• There came a white hart running into the hall
  with a white ______ next to him, and thirty
  couples of black hounds came running after them.
• Cf. cloze tests in psychology
• But, in CVA, reader seeks meaning or definition
• NOT a missing word or synonym Theres no
  correct answer!
• Co-text is what many mean by context
• BUT they shouldnt!

19
Proposed preliminary definitions

• The readers prior knowledge def
• the knowledge that the reader has when s/he
  begins to read the text
• and is able to recall as needed while reading
• knight picks up carries brachet ?? small
• Warnings
• knowledge ? truth
• so, prior beliefs is better
• prior vs. background vs. world, etc.
• See next slide!

20
Proposed preliminary definitions

• Possible synonyms for prior knowledge,
• each with different connotation
• Background knowledge
• Can use for information that author assumes
  reader to have
• World knowledge
• General factual knowledge about things other than
  the texts topic
• Domain knowledge
• Specialized, subject-specific knowledge about the
  texts topic
• Commonsense knowledge
• Knowledge everyone has
• E.g., CYC, cultural literacy (Hirsch)
• These overlap
• PK should include some CSK, might include some DK
• BK might include much DK

21
Steps towards aProper Definition of Context

• Step 1
• The context of X for a reader def
• The co-text of X
• the readers prior knowledge
• Both are needed!
• After reading
• the white brachet bit the hart in the buttock
• most subjects infer that brachets are (probably)
  animals, from
• That text, plus
• Available PK premise If x bites y, then x is
  (probably) an animal.
• Inference is not an enthymeme! (because )

22
Proper definition of context

• But (inference not an enthymeme because)
• When you read, you internalize the text
• You bring it into your mind
• Gärdenfors 1997, 1999 Jackendoff 2002
• This internalized text is more important than
  the actual words on paper
• Text Im going to put the cat out
• Misread as Im going to put the car out
• leads to different understanding of the text
• What matters is what the reader thinks the text
  is,
• Not what the text actually is
• Therefore

23
Proper definition of context

• Step 2
• The context of X for a reader def
• A single KB, consisting of
• The readers internalized co-text of X
• the readers prior knowledge

24
Proper definition of context

• But What is ?
• Not mere conjunction or union!
• Active readers make inferences while reading.
• From text a white brachet
• prior commonsense knowledge only physical
  objects have color,
• reader might infer that brachets are physical
  objects
• From The knight took up the brachet and rode
  away with the brachet.
• prior commonsense knowledge about size,
• reader might infer that brachet is small enough
  to be carried
• Whole gt S parts
• inference from internalized text PK ? new
  info not in text or in PK
• I.e., you can learn from reading!

25
Proper definition of context

• But Whole lt S parts!
• Reader can learn that some prior beliefs were
  mistaken
• Or reader can decide that text is mistaken
  (less likely)
• Reading CVA need belief revision!
• operation
• input PK internalized co-text
• output belief-revised integration of input,
  via
• Expansion
• addition of new beliefs from ICT into PK, plus
  new inferences
• Revision
• retraction of inconsistent prior beliefs together
  with inferences from them
• Consolidation
• eliminate further inconsistencies

26
Prior Knowledge
Text
PK1 PK2 PK3 PK4
27
Prior Knowledge
Text
T1
PK1 PK2 PK3 PK4
28
Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
29
B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
inference
P5
30
B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
T2
inference
P5
I(T2)
P6
31
B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
T2
inference
T3
P5
I(T2)
P6
I(T3)
32
B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
T2
inference
T3
P5
I(T2)
P6
I(T3)
33
Note All contextual reasoning is done in this
context
B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
P7
I(T1)
T2
inference
T3
P5
I(T2)
P6
I(T3)
34
Proper definition of context

• One more detail X needs to be internalized
• Context is a 3-place relation among
• Reader, word, and text
• Final(?) def.
• Let T be a text
• Let R be a reader of T
• Let X be a word in T (that is unknown to R)
• Let T-X be Xs co-text in T.
• Then
• The context that R should use to hypothesize a
  meaning for Rs internalization of X as it occurs
  in T def
• The belief-revised integration of Rs prior
  knowledge with Rs internalization of T-X.

35
This definition agrees with

• Cognitive-science reading-theoretic views of
  text understanding
• Schank 1982, Rumelhart 1985, etc.
• KRR techniques for text understanding
• Readers mind modeled by KB of prior knowledge
• Expressed in KR language (for us SNePS)
• Computational cognitive agent reads the text,
• integrating text info into its KB, and
• making inferences performing belief revision
  along the way
• When asked to define a word,
• Agent deductively searches this single,
  integrated KB for information to fill slots of a
  definition frame
• Agents context for CVA this single,
  integrated KB

36
Distinguishing Prior Knowledge from Integrated
Co-Text

• So KB can be disentangled as needed for belief
  revision or to control inference
• Each proposition in the single, integrated KB is
  marked with its source
• Originally from PK
• Originally from text
• Inferred
• Sources of premises

37
Some Open Questions

• Roles of spoken/visual/situative contexts
• Relation of CVA context to formal theories of
  context (e.g., McCarthy, Guha)
• Relation of I(T) to prior-KB e.g.
• Is I(Ti) true in prior-KB?
• It is accepted pro tem.
• Is I(T) a subcontext of pKB or B-R KB?
• How to activate relevant prior knowledge.
• Etc.

38
Summary

• People can figure out a meaning for a word from
  context, where
• Context belief-revised integration of
• readers prior knowledge, with
• internalized information from the text
• This clearer concept of relevant notion of
  context will help us
• evaluate other research
• develop our curriculum