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Steps Towards Formal Verification of Agent-based E-Business Applications

Nick Szirbik & Gerd Wagner

Eindhoven University of Technology

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Problem: Coherence in Business Processes

• Enforcing linguistic coherence: avoiding miscommunication by speaking the same language and sharing a common understanding of its terms.

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Problem: Coherence in Business Processes

• Enforcing linguistic coherence: avoiding miscommunication by speaking the same language and sharing a common understanding of its terms.

• Enforcing normative coherence: commitments, claims, and norms.

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Problem: Coherence in Business Processes

• Enforcing linguistic coherence: avoiding miscommunication by speaking the same language and sharing a common understanding of its terms.

• Enforcing normative coherence: commitments, claims, and norms.

• Enforcing process integrity by – verifying the correctness of interaction protocols (based on

safety and progress properties) at design time, and by– checking interaction constraints and handling exceptions at

runtime.

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What is a Business Process?

• A business process is a social interaction process among agents/actors.

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What is a Business Process?

• A business process is a social interaction process among agents/actors.

• An interaction process is a temporally ordered set of events and actions, perceived and performed by agents, and following a set of rules, or protocol, that is governed by norms, and that specifies the type of the interaction process.

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What is a Business Process?

• A business process is a social interaction process among agents/actors.

• An interaction process is a temporally ordered set of events and actions, perceived and performed by agents, and following a set of rules that specifies the type of the interaction process.

• A social interaction process emerges from the behavior of the participating agents.

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What is a Business Process?

• A business process is a social interaction process among agents/actors.

• An interaction process is a temporally ordered set of events and actions following a set of rules that specifies the type of the interaction process.

• A social interaction process emerges from the behavior of the participating agents.

• The behavior of an agent may be specified by means of reaction rules.

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What is an agent?

• Biological and artificial systems that interact with their (natural or virtual) environment on the basis of their mental state, and exhibit some degree of autonomy, are called "agents".

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What is an agent?

• Biological and artificial systems that interact with their (natural or virtual) environment on the basis of their mental state, and exhibit some degree of autonomy, are called "agents".

• The most basic mental components of an agent are its perceptions of events (in the form of incoming messages) and its beliefs (or knowledge).

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What is an agent?• Biological and artificial systems that interact with their

(natural or virtual) environment on the basis of their mental state, and exhibit some degree of autonomy, are called "agents".

• The most basic mental components of an agent are its perceptions of events (in the form of incoming messages) and its beliefs (or knowledge).

• Further important components are – memory about past events and actions, – commitments towards other agents to perform certain actions, – claims against other agents, – goals and intentions.

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Agent-Object-Relationship (AOR) Modeling

• an agent-oriented extension of Entity-Relationship diagrams, or UML-style class diagrams.

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Agent-Object-Relationship (AOR) Modeling

• an agent-oriented extension of Entity-Relationship diagrams, or UML-style class diagrams.

• makes an ontological distinction between active and passive entities, that is, between agents and ordinary objects.

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Agent-Object-Relationship (AOR) Modeling

• an agent-oriented extension of Entity-Relationship diagrams, or UML-style class diagrams.

• makes an ontological distinction between active and passive entities, that is, between agents and ordinary objects.

• an entity is either an agent, an action event, a commitment/claim, or an ordinary object.

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An AOR Interaction Pattern Diagram

DepLibrary CentralLibrary

confBookReq(...)

requestBook(?ISBN)

deliverBook(...)Book

Loan

R2

isAvailable

deliverBook(...)

BookCopy

Book

Loan

isAvailable

BookCopy

FacultyMember requestBook(

?ISBN) R1

R3confBookReq(...)

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Reaction Rules

ON Event RECEIVE requestBook(?ISBN) FROM ?DepLib

IF Condition BookCopy.isAvailable(?ISBN, ?InvNo)

THEN Action SEND confBookReq(?ISBN)

Effect CREATE COMMITMENT TOWARDS ?DepLib TO deliverBook(?ISBN) BY tomorrow();

CREATE BELIEF Loan(?DepLib, ?ISBN, ?InvNo, today())

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A reaction rule as a Petri net transition

Rule

InMsg

Cond

OutMsg

Effect

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Our Approach to Formal Analysis:

• Start with an expressive AOR model.

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Our Approach to Formal Analysis:

• Start with an expressive AOR model.

• Reduce the rule-based behavior specifications to a classical Petri net.

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Our Approach to Formal Analysis:

• Start with an expressive AOR model.

• Reduce the rule-based behavior specifications to a classical Petri net.

• Apply classical analysis techniques (e.g. with Woflan) to catch errors.

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Restrictions for obtaining classical Petri nets:

• the event term consists of an atom without content parameters

• the state condition consists of zero or more (possibly negated) propositional variables

• the action term consists of an atom without content parameters

• the effect expression consists of zero or more (possibly negated) propositional variables

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Mapping R1,R2,R3 into Petri Net Transitions

CentralLibraryDepLibrary

R1

requestBook

isAvailable

requestBook

isAvailable

R2

comm/claim todeliverBook

Loan

deliverBook

confBookReq

R3

confBookReq