Coursework Master’s Thesis Proposal

Coursework Master’s Coursework Master’s Thesis ProposalThesis Proposal

December 1999December 1999

University of South AustraliaUniversity of South Australia

School of Computer and Information ScienceSchool of Computer and Information Science

Student: David BennStudent: David Benn

Supervisor: Dan CorbettSupervisor: Dan Corbett

Implementing Conceptual Graph Processes Implementing Conceptual Graph Processes

David Benn, December 1999

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PlanPlan

• Conceptual Graphs

• Mineau’s Processes

• Implementing Processes

• Research Issues

• High-level Timeline

• References


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Conceptual GraphsConceptual Graphs• Sowa’s [1984] Conceptual Graphs (CGs)

represent knowledge via:– Concepts– Conceptual relations (relationships between

concepts)


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Conceptual GraphsConceptual Graphs• Sowa’s theory provides primitives to

model static knowledge.

• Permits modification of knowledge base (KB) via Canonical Formation Rules, e.g.– Copy– Join– Simplify


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Conceptual GraphsConceptual Graphsg1: [Feline: ](attr)[Carnivore]

g2: [Sitting]- (agent)[Cat: Elsie] (location)[Mat]

Join g1 and g2 to give g3

g3: [Sitting]- (agent)[Cat: Elsie]-

(attr)[Carnivore] (location)[Mat]

Feline

Cat Tiger Lion


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ProcessesProcesses• Dynamic updating of KB falls outside of

scope of theory.

• Mineau [1998] proposed processes as an extension to overcome this lack.

• Need arose from a R&D project to

capture knowledge about corporate

processes, e.g. fabrication of windows [Gerbe´, Keller & Mineau 1998].


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ProcessesProcesses

From [Gerbe´, Keller & Mineau 1998]

• Activity dependencies.• Inputs, outputs.• Precondition: before a

window can be assembled, a fabrication order must have been updated with frames and panes which conform to client order.

• Postconditions: when a frame is built, fabrication order is updated; likewise when a window pane is cut.


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ProcessesProcesses• [Gerbe´, Keller & Mineau 1998] outlined

a definition of processes in terms of activities and events but said nothing about mechanism.

• [Mineau 1998] introduced mechanism for processes in which:– Dynamic knowledge represented as state

transitions via pre and post conditions.– Applying postconditions consists of asserting

or retracting CGs in KB.


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ProcessesProcesses• Actors and demons are specialisations of

processes.– Actors take concepts and compute

individuals of pre-determined concept type. – Demons take concepts and return arbitrary

concept instances.– Processes take CGs as input and return

arbitrary CGs.

• Mineau emphasises simple process primitives which can be extended.


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Processes: mechanismProcesses: mechanism• A process consists of a rule set.

• Each rule is a pre/post condition pair.

• Process engine finds matching rule via preconditions and applies postconditions.

• Process takes ≥ 1 CG parameters, yields ≥ 1 CG outputs, asserts/retracts CGs.

process p (in g1...; out g2...) is { ri = prei;posti ,∀i ∈ 1,n[ ] }


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Processes: mechanismProcesses: mechanismA trivial algorithm:L0: int n = 1;

L1: while (n <= 10)

L2: n = n + 1;

Rule 0:

Pre0:[Line: L0](to_do)

Post0:[Integer: 1](value)[Variable:*n][Line: L0](done)[Line: L1](to_do)

[Mineau 1998] gives long partial definition for iterative factorial.

Following shows example rule set.

Trigger: [Line: L0](to_do)


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Processes: mechanismProcesses: mechanismRule 1a:

Pre1a:

[Line: L1](to_do)[Boolean: True]< ≤ >-

1-[Variable: *n] 2-[Integer: 10]

Post1a:

[Line: L1](done)[Line: L2](to_do)

actor

A trivial algorithm:L0: int n = 1;

L1: while (n <= 10)

L2: n = n + 1;


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Processes: mechanismProcesses: mechanismRule 1b:

Pre1b:

[Line: L1](to_do)[Boolean: False]< ≤ >-

1-[Variable: *n] 2-[Integer:

10]

Post1b:

[Line: L1](done)


L1: while (n <= 10)

L2: n = n + 1;


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Processes: mechanismProcesses: mechanismRule 2:

Pre2:

[Line: L2](to_do)

Post2:

[Variable: *n]-

(value)[Integer: *x]- < + >-

[Variable: *n] [Integer: 1]

[Line: L2](done)[Line: L1](to_do)


L1: while (n <= 10)

L2: n = n + 1;


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Implementing ProcessesImplementing Processes• “…there is only a theory which needs to

be refined, implemented, and applied.” [Mineau 1999b]

• Preliminary thoughts:– Need suitable way of expressing rules and processes

(i.e. a process language).

– Use Java for platform independence

– Use Notio framework [Southey & Linders 1999]• KBs, CGs, type lattices, CFRs, CGIF/LF reading/writing

– Use Mineau & Gerbe´’s [1997] contexts for rules.


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Digression: ContextsDigression: Contexts

[Human: Fred] (believes) [Statement: #]

[Entity: Earth]–(attr)[Shape: flat](attr)[Location: center_of_universe]

intention

extension

• Sowa [1984] introduced PROPOSITION concept type where referent is set of CGs.

• Mineau & Gerbe´ [1997] formalised contexts.• Intention constrains CGs in extension. (WoA)• Can be used to structure a KB.• Equations to extract graphs by intention, etc.• See Appendix A for overview of contexts.


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Research IssuesResearch Issues• How to represent processes

– Syntactically? Algorithmically?

– Can actors, demons, processes have one syntax & representation? Will latter be inefficient? (see p. 11)

• Retraction mechanism– (to_do) vs (done) in algorithm example– Erasure: replacing any CG with “blank”. [Sowa 1999]

• When should process engine stop?– Specify ≥ 1 rules upon which to stop?

– No more matching preconditions?

– Always run to completion or permit stop & restart?


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Research Issues (continued)Research Issues (continued)• Interaction with other systems (e.g. CharGer

[Delugach 1999]): CG import, export.• Behaviour of implementation vs original

conception. What has Mineau missed?• Applicability of process mechanism

– [Mineau 1998] only gave factorial as example.

– Needs to be demonstrated on more complex application, e.g. business processes, something more interesting?


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Other Research IssuesOther Research Issues• Automatic generation of rule sets. Difficult.• Soundness and completeness

– Do two postconditions conflict?

– [Mineau 1999a]: constraints on processes

• Conceptual Programming Environment– Logic and imperative programming.

– How does current work fit in with this goal (stated in [Mineau 1998])?

• Relationship to other work on dynamic CGs, dataflow languages, etc?

• Higher order processes?


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TimelineTimeline• Literature Review

(February, March)• Scope & features

(April)• Design & implement

(May, June, July)• Examples (August,

September)– Factorial– Business processes etc

• Write thesis (October, November)

Lit. Review

Scope

Implement

Examples

Write thesis


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ReferencesReferences[Delugach 1999] Delugach, H. CharGer: A Conceptual Graph Editor, [Accessed Online: December 1999], URL: http://www.cs.uah.edu/~delugach/CharGer/

[Gerbe´, Keller & Mineau 1998] Gerbe´, O., Keller, R., Mineau, G. Conceptual Graphs for Representing Business Processes in Corporate Memories. In Proceedings of the 6th International Conference on Conceptual Structures, pp. 401-415, 1998.

[Mineau & Gerbe´ 1997] Mineau, G. & Gerbe´, O. Contexts: A Formal Definition of Worlds of Assertions. In Proceedings of the 5th International Conference on Conceptual Structures, pp. 80-94, 1997.

[Mineau 1998] Mineau, G. From Actors to Processes: The Representation of Dynamic Knowledge Using Conceptual Graphs. In Proceedings of the 6th International Conference on Conceptual Structures, pp. 65-79, 1998.

[Mineau 1999a] Mineau, G. Constraints on Processes: Essential Elements for the Validation and Execution of Processes. In Proceedings of the 7th International Conference on Conceptual Structures, pp. 66-82, 1999.


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References (continued)References (continued)[Mineau 1999b] Mineau, G. E-mail correspondence from Guy Mineau to David Benn, 1st December, 1999.

[Southey & Linders 1999] Southey, F. & Linders, J.G., Notio — A Java API for developing CG tools. In Proceedings of the 7th International Conference on Conceptual Structures, 1999.

[Sowa 1984] Sowa, J., F. Conceptual Structures: Information Processing in Mind and Machine, Addison-Wesley, 1984.

[Sowa 1999] Sowa, J.F. et al, Conceptual Graph Standard, draft proposed American National Standard (dpANS) NCITS.T2/98-003, 1999. [Accessed Online: November 1999], URL: http://www.bestweb.net/~sowa/cg/cgdpansw.htm

[Sowa 2000] Sowa, J., F. Knowledge Representation: Logical, Philosophical, and Computational Foundations, Brooks/Cole, 2000.

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Coursework Master’s Thesis Proposal