FACS FACTS The Newsletter of the BCS Formal Aspects of Computing Science SIG Series 2 Vol 2 No1 May '91. Editorial 1 FACS Officers and Committee 2 FACS Reports 3 - 8 FACS Journal Contents 9 Refinement Workshop 10 LOTOS Papers 11 - 26 EATCS Contents 27-29 Notices 30-40 Forthcoming Events 41-50 Editor Jawed Siddiqi From now on we shall ensure that FACS FACTS like its sister publication the FACS journal will appear quarterly. Our target dispatch dates are the last days of the months of May, August, November and February. We are still having difficulty in obtaining "copy" for FACS FACTS, this might be b.ecause you are not sure what and when to send. FACS FACTS is an "open-newsletter" _ it welcomes contributions. The newsletter provides an excellent forum to get your early thoughts circulated and reviewed. So why not send us your draft research reports. You can also send notices of events like workshops and conferences. The submission dates are end of April, July, October and January. Jawed Siddiqi BCS-FACS Ofllcers (jenecal Iflcrnuers 1 , , Dr. A. J@remy J. Dick 'I' Chalrm~n: ,I Dr. D. John Cooke Bull Res@lIrch Department of Computer StudIes 68, Route de Versailles Loughborough UnIversIty of Technology 18430 Louveclennes I.OUGIIBOROUGII FRANCE LeIcestershire Tel: ~33 (I) 39 02 51 11 LEll 3TU FAX: ~33 (1) 39 02 49 77 Tel: (0509) 222616 E-mail: [email protected] FAX: (0509) 610815 E-mail: [email protected] Prof. Stephen J. Gold."ck Department of Computlno (Currently seconded to: Secretary: ImperIal Colleoe B. Tlm Denvlr 180, OUeen~ GlIte DTI 1 ITD Room 815 Praxis Systems Plc lIenslnoton IIlngsgate IIouse LONDON 20, H~nvers Street 66-14, Victoria Street BATII Sill 2Bt LONDON Tel: (011) 5895111 BAI IPX SWIE 6S11 Tel: (0225) 444700 FAX: (011) 581 8024 Tel: (011) 215 2353 FAX: (0225) U5205 E-mail: [email protected] E-maIl: [email protected] E-mail: [email protected] Dr. Richard J. Hltchell Treasurer: Department of ComputIng Or. ROQer G. Stone Brighton Polytechnic Oepa.rtment of Computer Studies Houlsecoomb Loughborough University of Technology BRIGHTON LOUGHBOROUGII Sussex I.elcesterohlre BN2 4GJ LEll 3TU Tel: (0213) 588641 lel: (0509) 222616 FAX: (0213) 571701 FAX: (0509) 610815 E-mail: [email protected] [-mall: [email protected] Roger Shaw Newsletter Editor: Performance Technology Group Dr. Jawed I. A. Slddlql Lloyds Reglster of Shipping Department of Computer Studies Lloyds Register IIouse School of Computing and Hanagement 29, Nellesley Road Sheffield City Polytechnic CROYDON 'DO Nn, f-)U S'l CRO 2AJ SIIEFFIEJ.D Tel: (081) 681 4818 Sl1 .".,D E-mail: [email protected] Tel: (0742) 120911 (direct: 5331551 m.g: 533153) [-mall: [email protected] Prof. Dan Simpson PUbllcIty: Department of Computing Dr. Brlan O. Honahan Brlohton Polytechnic Dr.partment of Computer Science Houlsecoomb The University of Hanchester Oxford Road BRIGIITON HIINCIIES1ER Sussex HI3 9PL BN2 4GJ Tel: (0213) 600900 ext: 2273 Tel: (061) 215 6131 FAX: (0213) 681752 FAX: (061) 215 6280 E-mail: [email protected] E-mail: bqm~uk.ac.man.cs Dr. Davld Till Specialist Groups Hanagement Committee Representative: Department of Computer Science Davld Blyth City University INCORD Ltd Northampton Square 15 Sherwood Avenue LONDON Ferndown ECIV OIlB WIHBORNE Tel: (011) 253,4399 Dorset FAX: (Dl1) 490 5028 01122 8JS E-mail: [email protected] Tel: (0202) 89683~ FAX: (0202/ 894834 Stephen Webster Department of Computing and Coonltlon Bournemouth Polytechnic Fern Barrow Dorset BCS-FACS Meeting on LOTOS 11 September 1990 A meeting on LOTOS, organised by the BCS-FACS group and sponsored by British Telecom, was held at Imperial College on 11 September 1990. LOTOS, Language Of Temporal Ordering Specification, has been adopted as . an International Standard for the specification of the behaviour of distributed, concurrent information processing systems; this meeting was put on with the intention of disseminating information about the nature of the language itself, the availability of support tools and the experience of some of those who are now using LOTOS in earnest. The day began with a tutorial on the language, presented by Ken Turner of Stirling University; no previous knowledge of the language was assumed, and the speaker gave a very comprehensible and gently humorous introduction to all aspects of the notation. The other talk before lunch was given by Paul Tilanus of Netherlands PTT Research. His topic was Tools for LOTOS, and he gave us an overwiew of the current state of play. Much of the work reported here was partly sponsored by the Esprit project LOTOSPHERE, currently the largest project working on LOTOS development; it was noted that the work on tools within LOTOSPHERE took as input tools created within the earlier SEDOS project. The speaker identified various phases in the specification life cycle and discussed the tools which would usefully support those phases. \ He mentioned text editors and syntax-directed editors for specification preparation, tools for syntax and static semantic analysis, simulators which allow the specifier to step through possible behaviours of the system to be specified, tools to perform correctness-preserving transformations or alternatively to check that proposed transformations are indeed correctness-preserving, "compilers" which can produce executable prototypes from a specification by taking note of additional comments which resolve non-deterministic aspects of the specification, and tools for automatic test generation and selection. At present, tools exist in each of the categories described here, but they are research products rather than production quality tools an~ in general are not yet able to handle specifications of the size encountered in industrial environments. The proceedings resumed after lunch with a talk by Robert Booth of British Telecom entitled Experience of using LOTOS for 051. Again the speaker was describing work done as part of the LOTOSPHERE project, specifically on the OSI Specification and Implementation Task. The aims of this Task are to use LOTOS in practice together with the methodology and tools developed in LOTOSPHERE; the application area is OSI Transaction Processing, chosen because this is a service which could be exploited widely for data processing, whilst being a complex standard not yet fully developed. < The work has a definitely industrial focus, aiming to employ technologies which can be used immediately in industry. Experience of such use should lead to refinement of the LOTOSPHERE methodology. Technology transfer and the building of confidence in the new techniques are important aims. Some facets of the LOTOSPHERE method are: LOTOS as a wide-spectrum language used to describe systems at many different levels of abstraction, identification and description of specification structuring styles such as constraint-oriented and state-oriented, transformation methods for moving from one style to another, simulation and testing, compilation and prototyping, the creation of a library of compiled LOTOS fragments .. Experience gained suggests that the notation has good expressive power within its intended field of application, though the inability to express timing constraints is felt to be a potential problem area. The ACT ONE component is found to be cumbersome for describing the kinds of data strucures needed in this Task. Testing is given a high profile by industrial users, but the speaker felt that simulation was a soft option, and in some cases had encouraged specifiers to modify their specifications in order to be executable. Tool performance is felt to be inadequate at present, that is to say, too slow on life-size specifications. The need is felt for some kind of module mechanism to be introduced into the language. Clazien Wezeman, also of British Telecom, then gave a talk on Conformance Testing and LOTOS. She discussed the idea of conformance, a concept which is inherently more complex than the notion of correct implementation for sequential systems since it has to take account of the possible reduction of non-determinism in an implementation. She contrasted the informal specification/informal conformance scenario with its formal counterpart. She stressed the need for testing even when formal specification and formal development techniques were used, and the main part of her talk was concerned with a method, known as CO-OP, which derives a formal description of a tester for a given system. The derivation is compositional, which is to say that given a system described as a composition of two simpler behaviours, then the tester for the composed system is itself composed from testers for the simpler behaviours. Further research will investigate the relation between this work and the ISO conformance testing Standard, will address the problem of test selection (even though we may be able to derive a formal description of a suitable tester we cannot in general exercise all possible behaviours), and will apply the method to life-size examples. Again the work reported here has taken place under the LOTOSPHERE umbrella, though it derives from earlier work in the Alvey FORMAP project. 4 Tommaso Bolognesi, of CNR-CNUCE Pisa, then spoke about Timed LOTOS: which way to go? As mentioned earlier, there is a felt need for the ability to express timing constraints. Many proposals for new features in LOTOS to satisfy this need have been put forward, but none has been universally welcomed as the definitive answer to the problem. The motivation behind these efforts is to provide realistic specification of time-dependent behaviour, and some formal basis for performance analysis. Any new features to be introduced must be sufficiently expressive and perspicuous; for example, specifiying explicitly the passing of time, represented by 'tick' events, is very tedious. An undesirable but predictable side effect of new timing features would be a more complex underlying theory, and consequent loss of analytic power.