NorduNet 2008 Helsinki.April 2008 Olaf Owe, Cristian Prisacariu,, Gerardo Schneider, Oslo University Seif Haridi, Pablo Giambiagi, Swedish Institute of Computer Science Joseph C. Okika, and Anders P. Ravn, Aalborg University NorduNet3 Project Contract-Oriented Software Development for Internet Services

Why Contracts ? Collaboration across organizational domains presumes trust, but… When trust is insufficient, use contracts

SOA and contracts The consumer either trusts the provider… … or they sign a contract which: – Determines the rights and obligations of each signatory – Usually states how the contract is to be monitored – Specify functional but also extra-functional qualities of the service: e.g. security, performance

How ? Developers need language support to program services that are: – Distributed – Interoperable – Discoverable – Contract-aware

The Marketplace Language/Approach Aspect Web Services (WS-*) Semantic Web (*-S) Electronic Business (eb-*) InterfaceWSDLOWL-SebBSI FunctionalityWS-BPEL, WSOLOWL-S (IOPE), WSMO ebBPSS ProtocolWS-BPEL, WS-CDLWSMO, OWL-SebBPSS SecurityWS-SecurityOWL-SebCPA(SecurityPolicy) QoSWS-Policy WS-Trust WSOL WSLA OWL-S WSMO WSML ebCPP(XMLDSIG) ebCPA

Key Issues for Contracts Definition Feasibility checking Compatibility checking Conformance checking Monitoring C C Ø C 1 C 2 P |= C P || I(C)

COSoDIS Mission develop novel approaches to implement and reason about contracts in a service oriented architecture. design and give proof of usefulness of system modeling tools and programming language tools to empower SOA developers to deploy highly- dynamic, negotiable and monitorable Internet services.

Formal modeling of contracts develop a model of contracts in a SOA A minimum requirement is to combine QoS specification and behavioral models (essential to constrain protocol implementation and to enforce confidentiality). develop practical and efficient methods to enforce information flow properties of realistic code, including cryptographic protocol implementations. 1.Johs H. Hammer and Gerardo Schneider, On the definition and policies of confidentiality 2.Cristian Prisacariu and Gerardo Schneider, A Formal Language for Electronic Contracts 3.Pablo Giambiagi, Olaf Owe, Anders P. Ravn, and Gerardo Schneider, Language-Based Support for Service Oriented Architectures: Future Directions C

Deontic Logic The logic of obligation (ought-to), permission, and prohibition is based on propositional and modal logics. ought-to-do expressions consider names of actions: The Internet Provider ought to send a password to the Client ought-to-be expressions consider results of actions The average bandwidth ought to be more than 20kb/s Georg H. von Wright started to sustain a logic of actions We consider Obligation, Permission and Prohibition over actions only

Programming language support for contracts extend Creol with wrapper primitives for correct-by-construction wrapped code. contracts for QoS and confidentiality will be modeled as first-class entities develop techniques for constructing monitors from contracts. 1.A. Torjusen, Olaf Owe, and Gerardo Schneider, Towards integration of XML in the Creol object- oriented language 2.Olaf Owe, Gerardo Schneider, and Martin Steffen, Components, Objects, and Contracts P |= C P || I(C)

Reasoning about contracts extraction of models to facilitate reasoning about contracts. timing constraints will be mapped to timed automata using the Maude tools for model checking and exhaustive search. 1.Emilia Cambronero, Joseph C. Okika, and Anders P. Ravn, Analyzing Web Service Contracts - An Aspect Oriented Approach 2.Gordon Pace, Cristian Prisacariu, and Gerardo Schneider, Model Checking Contracts -a case study C Ø C 1 C 2

Web Service Analyses WS-BPELWS-CDL (Timed) Automata translation Timed Automata translation C Ø

Compatibility WS-BPELWS-CDL (Timed) Automata Timed Automata ? C 1 C 2

Contract Patterns and Case Studies establishing representative examples, equipping them with suitable contracts. distill some useful contract patterns provide corresponding verification patterns. 1.Zhenbang Chen, Zhiming Liu, Volker Stolz, Lu Yang, and Anders P. Ravn, A refinement driven component-based design 2.Sakyibea Darko-Ampem, Maria Katsoufi, and Pablo Giambiagi, Secure Negotiation in Virtual Organizations

Fitting it Together Applications Models WS-CDL Implement- ations. Creol, Java, etc WS-BPEL Platform Policies (Contract templates) Service-Level Agreement Contracts (e.g. CL) Verification certificates RV -> monitors | | | Logics.

Expected Results A modal logic for defining high level contracts Model checking tools for checking WS*-style contracts Larger Case Study? CoCoME Monitoring? C C Ø C 1 C 2 P |= C P || I(C)

Conclusion SOA is here to stay Independent development needs contracts Contracts must be checkable Checking tools are reaching maturity The challenge: Fit the pieces together