Components, objects, and contracts

ABSTRACT

Being a composite part of a larger system, a crucial feature of a component is its interface, as it describes the component's interaction with the rest of the system in an abstract manner. It is now commonly accepted that simple syntactic interfaces are not expressive enough for components, and the trend is towards behavioral interfaces.

We propose to go a step further and enhance components with deontic contracts, i.e., agreements between two or more components on what they are obliged, permitted, and forbidden to do when interacting. This way, contracts are modeled after legal contracts from conventional business or judicial arenas. Indeed, our work aims at a framework for e-contracts, i.e., "electronic" versions of legal documents describing the parties' respective duties.

We take the object-oriented, concurrent programming language Creol as starting point and extend it with a notion of components. We then discuss a framework where components are accompanied by contracts and we sketch some ideas on how analysis of compatibility and compositionality could be done in such a setting.

REFERENCES

• 1: COSDIS. www.ifi.uio.no/~gerardo/nordunet3, 2007.
• 2: Credo. www.cwi.nl/projects/credo/, 2006.
• 3: Creol. www.ifi.uio.no/~creol, 2007.
• 4: Einar Broch Johnsen , Olaf Owe, An Asynchronous Communication Model for Distributed Concurrent Objects, Proceedings of the Software Engineering and Formal Methods, Second International Conference, p.188-197, September 28-30, 2004 [doi>10.1109/SEFM.2004.6]
• 5: Einar Broch Johnsen , Olaf Owe , Ingrid Chieh Yu, Creol: a type-safe object-oriented model for distributed concurrent systems, Theoretical Computer Science, v.365 n.1, p.23-66, 10 November 2006 [doi>10.1016/j.tcs.2006.07.031]
• 6: Bertrand Meyer, Eiffel: the language, Prentice-Hall, Inc., Upper Saddle River, NJ, 1992
• 7: O. Owe, G. Schneider, and M. Steffen. Components, objects, and contracts. Technical Report 363, Dept. of Informatics, Univ. of Oslo, Norway, August 2007.
• 8: G. Pace, C. Prisacariu, and G. Schneider. Model checking contracts --- a case study. In ATVA'07, volume 4762 of LNCS, pages 82--97, 2007.
• 9: C. Prisacariu and G. Schneider. A formal language for electronic contracts. In FMOODS'07, volume 4468 of LNCS, pages 174--189, 2007.
• 10: WSLA. www.research.ibm.com/wsla/.

INDEX TERMS

Primary Classification:
  D. Software
  D.2 SOFTWARE ENGINEERING
        D.2.13 Reusable Software

Additional Classification:
  D. Software
  D.1 PROGRAMMING TECHNIQUES
      D.1.3 Concurrent Programming
      D.1.5 Object-oriented Programming

  F. Theory of Computation
  F.3 LOGICS AND MEANINGS OF PROGRAMS
      F.3.1 Specifying and Verifying and Reasoning about Programs

General Terms:
Verification

Keywords:
Creol, components, compositionality, contracts, deontic logic, interfaces, object-orientation