Nessun titolo diapositiva

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Agent Oriented modeling by interleaving formal
and informal analysis
Anna Perini1, Marco Pistore2,1, Marco Roveri1,
Angelo Susi1 1ITC - IRST Via Sommarive, 18,
I-38050, Trento-Povo, Italy perini,roveri,susi_at_i
rst.itc.it 2DIT, University of Trento Via
Sommarive, 14, I-38050, Trento-Povo,
Italy pistore_at_dit.unitn.it
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Introduction

• What
• Exploitation of Formal Techniques to guide and
  support the analyst while building and refining
  Conceptual Models
• Why
• Visual conceptual modeling is a core process in
  software development (RUP / AGILE)
• Weakness lack of a formal semantics
• Formal specifications languages provide a precise
  semantics
• Weakness require strong skills, often
  ineffective for discussing with the stakeholders
• How
• Defining a framework which uses diagrammatic
  models equipped with formal semantics
• Agent Oriented approach (TROPOS)
• Focus on Requisites specification

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Outline

• Introduction ?
• Tropos by Example
• Informal modeling via Informal Tropos
• Formal modeling via Formal Tropos
• The framework
• Model assessment and refinement
• Model validation
• Model evolution
• Conclusions Future Work

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AO Visual Modeling with Tropos
Software development activities
Early Requirements
Late Requirement
Architectural Design

Actors in the organizational setting
System Actor
Sub-system Actors
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The example Informal modeling

• Methodology
• Provides three
• Goal analysis
• Techniques
• AND/OR decomp.
• Means-end analysis
• Contribution

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Informal Analysis via Tropos

• Benefits
• Language ontology based on common sense
  (informal) components (actors, goals,
  dependencies )
• A graphical notation
• Reasoning mechanisms AND/OR goal decomposition,
  means-end analysis, goal contribution analysis,
  that allow to model the why domain and system
  requirements
• Weaknesses
• Static view of the model (no dynamics for the
  generation and achievement of goals, needs,
  dependencies )
• No temporal constraints (e.g., on the fulfillment
  of goals and dependencies)

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The Example Formal modeling

• A Formal Tropos specification consists of a
  sequence of class declarations such as actors,
  goals and dependencies, that represents the
  formal counterpart of the objects in the informal
  specification
• Extends a Tropos specification with annotations
  that characterize the valid behaviors of the
  model

• Actor Advisor
• Actor Producer
• Goal ManagePheromoneTrapPlant
• Goal Area Collection
• Actor Advisor
• Mode achieve
• Attribute mptp ManagePheromoneTrapPlant
• Creation Condition not Fulfilled(mptp)
• Fulfillment condition
• ? pp PlantPlan (pp.actoractor
  Fulfilled(pp))
• Goal Dependency OrchardsData

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The Example Formal modeling

• A Formal Tropos specification consists of a
  sequence of class declarations such as actors,
  goals and dependencies, that represents the
  formal counterpart of the objects in the informal
  specification
• Extends a Tropos specification with annotations
  that characterize the valid behaviors of the
  model

• Actor Advisor
• Actor Producer
• Goal ManagePheromoneTrapPlant
• Goal Area Collection
• Actor Advisor
• Mode achieve
• Attribute mptp ManagePheromoneTrapPlant
• Creation Condition not Fulfilled(mptp)
• Fulfillment condition
• ? pp PlantPlan (pp.actoractor
  Fulfilled(pp))
• Goal Dependency OrchardsData

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Formal Analysis via Tropos

• Benefits
• The introduction of the temporal dimension in
  Tropos Representation allow to produce scenarios
  to be validated by the stakeholders
• Domain representation can be Formally Verified
  (proof, counterexamples to correct the domain
  specification)
• Weaknesses
• Formal languages are expressive but yet hard to
  be understood (temporal constraints are expressed
  via a typed first-order linear time temporal
  logic LTL)
• Formal Results are hard to interpret in the
  informal setting

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The framework

• We propose a framework based on the idea of
  exploiting formal techniques to guide and support
  the analyst while building and refining a
  conceptual model
• The framework has to support
• Model assessment and refinement, against possible
  inadequacies
• Model validation, with the stakeholders, to end
  up with an agreed set of requirements
• Model evolution, maintaining its consistency,
  propagating changes, merging redundant
  information
• The framework will include a tool for
• an automatic translation from Informal to Formal
• visualization of the query results

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Model Assessment Refinement

• The Informal Analyst assesses the model against
  possible inconsistencies or redundancies or
  critical elements and eventually refines the
  informal model on the basis of the new answer of
  the Formal Analyst to his/her question

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Model Assessment Refinement (2)

• Is It possible for the Advisor to perform
  historical data analysis ?
• FULFILLABLE HistoricalDataAnalysis

Query
Results
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Model Assessment Refinement (3)

• Is It possible for the Advisor to perform
  historical data analysis without consulting the
  Producer?
• NONCRITICAL Producer FOR HistoricalDataAnalysis

Query
Results
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Model Validation

• The informal Analyst looks for relevant
  validation cases to be proposed to the
  stakeholder in order to drive the validation
  process and to end up with an agreed model

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Model Validation

• How does the Advisor usually operate? Is that
  he/she always satisfies the goal area collection
  after satisfying all its sub-goals, according to
  the following sequence area analysis via GIS,
  plant plan and finally dispenser report and
  order?
• FULFILL AreaAnalysisViaGIS THEN PlantPlan THEN
  DispenserReportAndOrder THEN AreaCollection

PlantPlan
DispenserReportAndOrder
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Conclusion

• Lightweight usage of Formal Methods
• Formal model is extracted automatically by an
  annotated informal model
• Formal model properties to be verified are
  obtained from queries in a user friendly language
• Witnesses and counter-examples are graphical

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Conclusion (2)
Informal Model
Graphical Editor
Natural Language Query
High Level Lang. Query
Formal Tropos Query
Verification Engine
Formal Tropos Results
Visual Results
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Future Work
Informal Model
Graphical Editor
Visual Query
MODELER
High Level Lang. Query
THE TOOL
Formal Tropos Query
Verification Engine (NuSMV)
Formal Tropos Results
Visual Results
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Future Work

• We are validating the framework respect to other
  software development activities
• We are now involved in the design of the tool
  that supports
• The build up of the modeler components
• The management of the informal diagram via graph
  rewriting techniques
• The high level language to temporal logic queries
  translator
• The implementation of visualization functions to
  show the formal results to the informal analyst

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References

• T-Tool http//sra.itc.it/tools/t-tool
• Tropos http//science.unitn.it/tropos

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LTL query formula

• Global Possibility
• F ( ? aAdvisor
• (? hadHistoricalDataAnalysis
• (had.actor a ? Fulfilled(had))))