Contextualization: an Abstraction Mechanism for Conceptual Modeling

1
Contextualizationan Abstraction Mechanism for
Conceptual Modeling
Joint work by Manos Theodorakis Anastasia
Analyti Nicolas Spyratos Panos
Constantopoulos Institute of Computer
Science FORTH-ICS Greece
2
Outline

• Why we need contexts
• Context definition
• Structuring the contents of a context
• Formal Theory
• Operations on contexts
• Applications
• Future Work
• Conclusions

3
Different Perceptions
Ontology of mechanic for house
Different Perceptions
Ontology of family for house
4
Other examples of context

• Distributed databases
• Travel agencies
• Anatomical map
• Natural language
• Ambiguity resolution
• Organization of large databases

5
Context features

• Viewing the information from different viewpoints
• Support for context-dependent meaning
• Viewing information at different levels of detail
• Modular design
• context-dependent reachability
• Support for synonyms, homonyms

6
Contextual Ontologies

• Organize in a single framework,
• several contextual representations
• Reasoning based on contextual representations

7
Our Definition of Context
Context
names of o
object o
reference of o (another context)
. . .
A context is a set of objects, in which each
object is associated with a set of names and
(possibly) a reference to an other context.
8
Example
c3
c1
Greeece o0
Dining o8
Crete, Kriti o3
Hotels o9
c0
Athens, Athina o5
Transportation o10
c10
Tourist Guide o1
History o16
Geography o2
Map o4
Geography o2
c5
c2
c14
Crete o3
c15
Attiki o6
c6
Map o7

• Support for synonyms, homonyms

• Object Sharing

• Context-dependent naming, referencing
• Viewing the information from different
  viewpoints
• Viewing information at different level of detail

9
Structuring the contents of a context

• attr(attr_obj,from,to)
• in(in_obj,from,to)
• isa(isa_obj,from,to)

c4
City o6
Village o7
o11
A o10
Chandax o8
Fortification o9
c5
c3
City o6
Village o7
Crete o4
o14
. . .
B o12
Heraklion o8
A o10
in
Airport o13
10
Attribution - Contextualization
Demographic Data o1
c1
related to o4
Persons o2
Places o3
c4
c3
c2
born in o11
Place o3
Person o2
Company o13
located in o14
Student o6
Foreign Country o6
works for o12
Employee o7
Domestic Location o7
no of years o16
Integer o15
isa
11
Generalization - Contextualization
c0
Organization o1
Hospital o2
isa
Refinement Relation
12
Classification - Contextualization
cd
. . .
c1
Schema 2 o2
Schema 1 o1
cin
. . .
. . .
Instance 1 o
Instance 2 o4
c

• The same set of objects can be classified
  under different schemas

• Several set of objects can be classified under
  the same schema

in
13
Context theory

• Formal definitions
• Model theory
• Set of sound complete inference rules.

14
Formal Definitions
Basic Sets O set of Objects CXT set of
Contexts N set of Names
Reference Paths RPc set of reference paths
starting from the objects of c
Contents of a context cnts(c)
Contextualized IB
15
Predicates - Functions
Predicates
Functions
16
Inference System
1. ISA Reflexivity
2. ISA Transitivity
3. Context Refinement
4. Refinement Reflexivity
5. Refinement Transitivity
6. Instance Upward Inheritance
17
Inference System
7. Inheritance of Built-in Information
8. Interaction between Generalization-Contextualiz
ation
9. Interaction between Classification-Generalizati
on-Contextualization
18
Refinement, Equivalence Relations
Refinement Relation
Equivalence Relation
19
Operations for Creating and Maintaining Contexts

• CreateCxt(ltcontentsgt)
• insert( o, N, c )
• deleteObj( o, c )
• deleteName( o, n, c )
• copyCxt( c )
• deepCopyCxt( c )

• Union
• Intersection
• Difference

20
Context Union
InfSys DSS
InfSys o10
Dinos, Xulouris o1
Head o2
Nick, Nikos o4
Dinos o6
c4
DSS o20
c5
InfSys o10
Dinos o6
c4
DSS o20
Head o2
Xilouris o1
21
Context Intersection
InfSys DSS
InfSys o10
Dinos, Xilouris o1
Head o2
InfSys o10
c/5
c4
DSS o20
Dinos o1
Dinos o6
DSS o20
Head o2
Head o2
Xilouris o1
c/4
Head o2
Xilouris o1
22
Context Difference
c1
Manos View o1
Dr_Xilouris o1
o4
DSS o20
InfSys o10
Nicolas View o2
Manos View y Nicolas View
o4
DSS o20
InfSys o10
Manos View o1
23
(No Transcript)
24
Constraint Well-definedness
c2
A o1
c1
A, B o1
G o3
A o2
C o6
o3
D o4
c3
B o1
E o5
C o2
A o6

• A context is called Well-defined iff
• There is a name path that uniquely identifies
  each object
• recursively contained in the context
• Acyclicity

Theorem Closure of well-definedness under Union,
Intersection and Difference
25
Applications

• Partial View Support
• Different people have different views of the same
  resources
• Different applications have different
  (goal-oriented) models of the same resources
• Cooperative work
• Workspaces Private, Group, Public
• Ontology Integration/Merging
• Web search
• Modelling of user interests/Reply based on query
  context

26
Applications (cont.)Pervasive computing

• Agent context
• Redefined contexts of agent situations
• Central Manager
• Collects Agent Contexts
• Reasons about them
• Maintains consistency

27
Future Work

• Extension of the web ontology languages RDF and
  OWL with contexts
• Querying and reasoning with
• contextualized RDF
• contextualized OWL

28
Conclusions

• A formal notion of context in information
  modeling
• Formal definition
• Core axioms
• Operations
• Supported features
• Partial views
• Relative semantics
• Modular design

29
Thank you!