1. research & development Towards a Versatile Contract Model to Organize Behavioral Specifications Philippe Collet 1, Alain Ozanne 2 and Nicolas Rivierre 2 1. University of Nice, I3S Laboratory, France 2. France Telecom R&D, France

2. research & development France Telecom Group title of document/date/author – p 2 Requirements: - Dependability : assembly validity (requirements satisfaction), - Robustness : diagnosis, failure repair, Context: Assembled Applications servicecomponent Locks : - Properties complexity : kinds: QoS (SLA..), behavior (service interaction…), … [Beugnard] formalisms: CQML, Quo, assertions, Behavior Protocol… - Dynamic evolutions Sound Composition

3. research & development France Telecom Group title of document/date/author – p 3 Motivations and Requirements A tool to improve the composition dependability A tool that deals with various properties and verifications means A tool compatible with the dynamic evolutions of architectures A tool conceptually as secure and explicit as real life contracts

4. research & development France Telecom Group title of document/date/author – p 4 Goal: a Contracting Framework A framework that contractually: P1 : Makes explicit the conformity of individual components with their specification Conformity P2 : Makes explicit, for a configuration of components, the compatibility of their specifications Compatibility P3 : Makes explicit the responsibilities of the components against their specifications Responsibilities P4 : Supports various specification formalisms and verification techniques Formalisms

5. research & development France Telecom Group title of document/date/author – p 5 Related Work Conformity Compatibility Responsibility Various formalisms Existing frameworks Goal J2EE

6. research & development France Telecom Group title of document/date/author – p 6 System Interface Contract assertion scope = interface ConFract: - Assertions associated with a component - Components conformity to assertions - Associated responsibility External Composition Contract assertion scope = components outside Internal Composition Contract assertion scope = composites inside

7. research & development France Telecom Group title of document/date/author – p 7 Contract Model Participant Clause Participant Clause Agreement Assumption Guarantee Assumption Clause Assumption Guarantee Clauses satisfaction + Agreement satisfaction => Sound Composition

8. research & development France Telecom Group title of document/date/author – p 8 Contract and Formalisms Generic Contract : Constraint description : Contract { Participants : * ; Clauses : { clause : responsible : ; assumption : guarantee : } * Agreement : { agreement : *} } On Observe : ( val : at : ; ) + Verify : P1 P3P2 P4 Component specification Contractual formalism

9. research & development France Telecom Group title of document/date/author – p 9 Behavior Protocols Expressions specifying sequences of communication events: Emitted and received method calls and returns of method calls On the interfaces of one component ("frame protocol") On the outside interfaces of an assembly of sub-components ("architecture protocol") Regular-like expressions : (?ppt.enable; !csp.setThrottle*; ?ppt.disable)* Tools are provided to check Implementation conformity Protocols compatibility (horizontal and vertical)

10. research & development France Telecom Group title of document/date/author – p 10 Application of Behavior Protocols (?ppt.enable; !csp.setThrottle*; ?ppt.disable)* ?sns.engineOn; (?sns.on; !ppt.enable; (?sns.accelerate + ?sns.brake + ?sns.off)*; !ppt.disable)* + ?sns.engineOff ?sns.engineOn; (?sns.on; !csp.setThrottle*; (?sns.accelerate + ?sns.brake + ?sns.off)*)* + ?sns.engineOff

11. research & development France Telecom Group title of document/date/author – p 11 Resulting Contract (1/2) Frame protocols as clauses : Contract : Participants :,, ;... Clause : responsible : assumption : On Observe : val : at entry ppt.*; Verify : runtimeCheck(speedCtrlFP); guarantee : On Observe : val : at entry csp.*; Verify : runtimeCheck(speedCtrlFP);... speedCtrlFP = (?ppt.enable; !csp.setThrottle*; ?ppt.disable)* pptcsp

12. research & development France Telecom Group title of document/date/author – p 12 Resulting Contract (2/2) Agreement : Contract : Participants :,, ;... Agreement : On Observe : val : at : entry.start Verify : verticalCheck (cruiseCtrlFP, parallelCheck (sensorCtrlFP, speedCtrlFP)) verticalCheck parallelCheck

13. research & development France Telecom Group title of document/date/author – p 13 Contract for Assertion-based Formalism float getResponseTime(float throttle) csp Clause : A = G = A = pre : throttle > 10 post : return > 0 Client side pre : throttle > 0 post : return > 10 Server side Agreement : return > 10 => return > 0 throttle > 10 => throttle > 0

14. research & development France Telecom Group title of document/date/author – p 14 Integration and Use Framework R1. Formalisms integrator R2.Domain specifier R3. User of the results of the contract evaluation RoleProvidesMechanismObtains R1Adapter (Plugin) : Formalism translator Integration to the framework core A contract builder and checker R2Specifications, SystemBuildingContracts R3-CheckingGarantuees / diagnosis Fractal System Pre/post conditions Example of use with an assertion translator : Guarantee Checking Observations Contractual Spec.Contract Building

15. research & development France Telecom Group title of document/date/author – p 15 Conclusion Operational contract model for components architecture Supports the expected properties provided that: Specifications can be translated in assumption-guarantee constraints Specifications have tools for checking conformity and compatibility Simple and pragmatic principles for software architects Future works : Vertical composition of contracts between consecutive levels of nesting (when the formalism supports it), Application to other architectural platforms (components, services…)

16. research & development France Telecom Group title of document/date/author – p 16 Questions