AOSE-2003, Melbourne July 15 th 1 Agent Oriented modeling by interleaving formal and informal analysis Anna Perini 1, Marco Pistore 2,1, Marco Roveri 1, Angelo Susi 1 1 ITC - IRST Via Sommarive, 18, I-38050, Trento-Povo, Italy 2 DIT, University of Trento Via Sommarive, 14, I-38050, Trento-Povo, Italy

AOSE-2003, Melbourne July 15 th 2 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

AOSE-2003, Melbourne July 15 th 3 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

AOSE-2003, Melbourne July 15 th 4 AO Visual Modeling with Tropos Early Requirements Late Requirement Architectural Design Software development activities Actors in the organizational setting System Actor Sub-system Actors

AOSE-2003, Melbourne July 15 th 5 The example: Informal modeling Methodology Provides three Goal analysis Techniques: AND/OR decomp. Means-end analysis Contribution

AOSE-2003, Melbourne July 15 th 6 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)

AOSE-2003, Melbourne July 15 th 7 The Example: Formal modeling 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.actor=actor & Fulfilled(pp)) & … …… Goal Dependency OrchardsData …… 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

AOSE-2003, Melbourne July 15 th 8 The Example: Formal modeling 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.actor=actor & Fulfilled(pp)) & … …… Goal Dependency OrchardsData …… 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

AOSE-2003, Melbourne July 15 th 9 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

AOSE-2003, Melbourne July 15 th 10 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 The framework

AOSE-2003, Melbourne July 15 th 11 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 Model Assessment & Refinement

AOSE-2003, Melbourne July 15 th 12 Model Assessment & Refinement (2) Is It possible for the Advisor to perform historical data analysis ? FULFILLABLE HistoricalDataAnalysis Manage Pheromone trap plant Historical Data analysis Orchards historical Data Manage Pheromone trap plant Historical Data analysis Orchards historical Data Orchards Data Producer Manage Pheromone trap plant Historical Data analysis Orchards historical Data Orchards Data Producer Manage Pheromone trap plant Historical Data analysis Orchards historical Data Orchards Data Producer Manage Pheromone trap plant Historical Data analysis Orchards historical Data Orchards Data Producer Advisor Manage Pheromone trap plant Historical Data analysis Query Results

AOSE-2003, Melbourne July 15 th 13 Model Assessment & Refinement (3) Is It possible for the Advisor to perform historical data analysis without consulting the Producer? NONCRITICAL Producer FOR HistoricalDataAnalysis Manage Pheromone trap plant Historical Data analysis Monitoring Devices data Manage Pheromone trap plant Historical Data analysis Monitoring Devices data Advisor Manage Pheromone trap plant Historical Data analysis Query Results Manage Pheromone trap plant Historical Data analysis Monitoring Devices data Orchards historical Data Orchards Data Producer

AOSE-2003, Melbourne July 15 th 14 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

AOSE-2003, Melbourne July 15 th 15 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 DispenserReportAndOrder PlantPlan

AOSE-2003, Melbourne July 15 th 16 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

AOSE-2003, Melbourne July 15 th 17 Conclusion (2) Informal Model Natural Language Query High Level Lang. Query Formal Tropos Query Visual Results Graphical Editor Verification Engine Formal Tropos Results

AOSE-2003, Melbourne July 15 th 18 Future Work Informal Model High Level Lang. Query Formal Tropos Query Visual Results Graphical Editor Verification Engine (NuSMV) Formal Tropos Results MODELER THE TOOL Visual Query

AOSE-2003, Melbourne July 15 th 19 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

AOSE-2003, Melbourne July 15 th 20 References T-Tool: Tropos:

AOSE-2003, Melbourne July 15 th 21 LTL query formula Global Possibility F (  a:Advisor ( had:HistoricalDataAnalysis (had.actor = a  Fulfilled(had))))