Abstract
We explore different approaches to modelling external choice as a reactive process in a UTP semantics with discrete time. The standard definition of external choice cannot be simply reused in a timed semantics, since it can introduces behaviours which are not prefix-closed and urgent events which occur instantly. We first examine unstable states and urgent events in different semantics for CSP. We present the semantics for a simple timed reactive UTP language and describe the difficulties of adding external choice. We define two new process operators; strict choice, which never engages in urgent events and lazy choice, which can delay urgent events. We briefly discuss two potential modifications to the language model; a lazy semantics, in which termination is not unstable, and a semantics in which unstable states can be observed. Finally, we give a more detailed treatment to strict choice, expressing it as a reactive design and stating its algebraic laws.
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References
Bryans, J., Canham, S., Cavalcanti, A., Sampiao, A., Santos, T., Woodcock, J.: CML Definition 2. Public Document. Deliverable Number: D23.3, Version: 1.0, COMPASS Project, University of York, March 2013
Butterfield, A., Gancarski, P., Woodcock, J.: State visibility and communication in unifying theories of programming. In: Theoretical Aspects of Software Engineering, pp. 47–54 (2009)
Cavalcanti, A., Woodcock, J.: A tutorial introduction to CSP in unifying theories of programming. In: Cavalcanti, A., Sampaio, A., Woodcock, J. (eds.) PSSE 2004. LNCS, vol. 3167, pp. 220–268. Springer, Heidelberg (2006)
Hoare, C.A.R.: Communicating Sequential Processes. Intl. Series in Computer Science. Prentice Hall (1985)
Hoare, C.A.R., He, J.: Unifying Theories of Programming. Series in Computer Science. Prentice Hall (1998)
Lowe, G., Ouaknine, J.: On timed models and full abstraction. Electr. Notes Theor. Comput. Sci. 155, 497–519 (2006)
Roscoe, A.W.: The Theory and Practice of Concurrency. Prentice-Hall Series in Computer Science. Prentice-Hall (1998)
Sherif, A.: A Framework for Specification and Validation of Real-Time Systems using Circus Actions. PhD thesis, Center of Informatics - Federal University of Pernambuco, Brazil (2006)
Wei, K., Woodcock, J., Cavalcanti, A.: Circus time with reactive designs. In: Wolff, B., Gaudel, M.-C., Feliachi, A. (eds.) UTP 2012. LNCS, vol. 7681, pp. 68–87. Springer, Heidelberg (2013)
Woodcock, J., Cavalcanti, A.: A concurrent language for refinement. In: Butterfield, A., Pahl, C. (eds.) IWFM 2001: 5th Irish Workshop in Formal Methods. BCS Electronic Workshops in Computing, Dublin, Ireland, July 2001
Woodcock, J., Cavalcanti, A.: The semantics of \({circus}\). In: Bert, D., Bowen, J.P., Henson, M.C., Robinson, K. (eds.) ZB 2002. LNCS, vol. 2272, pp. 184–203. Springer, Heidelberg (2002)
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Canham, S., Woodcock, J. (2015). Three Approaches to Timed External Choice in UTP. In: Naumann, D. (eds) Unifying Theories of Programming. UTP 2014. Lecture Notes in Computer Science(), vol 8963. Springer, Cham. https://doi.org/10.1007/978-3-319-14806-9_1
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DOI: https://doi.org/10.1007/978-3-319-14806-9_1
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