G. Leduc and L. L'eonard. A timed lotos supporting dense time domain and including new timed operators. Formal Description Techniques, V:87--182, 1993.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....one. Although we could also have defined such a new operator ourselves we have not done so because adding new real time operators increases the complexity 17 of the semantics and can have subtle, unanticipated side effects. For instance, when a delay operator is added to an algebra like LOTOS [16], we note that it can interact with other operators in unfortunate ways. If such a delay is used as the second operand to the LOTOS disabling operator then the combined behaviour no longer enjoys the simple recursive definition normally possible by unwinding the disabling operator as a choice ....

G. Leduc and L. L'eonard. A timed LOTOS supporting a dense time domain and including new timed operators. In M. Diaz and R. Groz, editors, Formal Description Techniques, V, pages 87--102. North-Holland, 1992.

....of equivalences related to timed semantics is given. In Section 4, a simple but practical example is provided. Section 5 concludes this paper. We say that an action is urgent if the action must necessarily be executed at the current time. The urgency issue is mentioned in many papers including [11, 12]. 3 2. Definitions 2.1. Syntax The syntax of LOTOS T is defined as follows. Definition 1 Behaviour expressions of LOTOS T are defined as follows (the priority of operators are analogous to LOTOS) E : stop exit a; E a[P(t, E EI[A]I E E hide A in E p[gl, non temporal ....

G. Leduc and L. Lonard, "A timed LOTOS supporting a dense time domain and including new timed operators," in Formal Description Techniques, V, pp. 87-102, IFIP, North-Holland, 1993.

....and protocols requires timing mechanisms such as timeouts, watchdogs, delays and isochronous data transfers. In the last few years, many FDTs with constructs to model the above mechanisms have been proposed. These timed FDTs are mainly based on extensions of asynchronous process algebras, see [11, 7] for an overview. FDTs need supporting tools to allow automatic verification of requirements. ET LOTOS [8] is a timed extension of LOTOS that allows the modeling of real time behaviors. Kronos [12, 10] is a tool that checks whether a real time system described by a timed automaton (automaton ....

G. Leduc and L. L'eonard. A timed LOTOS supporting dense time domain and including new timed operators. In Formal Description Techniques V, pages 87--102. North-Holland, 1993.

....time and probability are not only worth for the expressiveness of the language, but also because they allow to study a wider and richer range of properties over the processes of the language. In the last years there have been several proposals for the inclusion of timed information in Lotos (e.g. [16, 11, 12]) using different approaches to introduce time; for example, in [12] the improved version of [11] an operator similar to that in [23] is used, denoting that an action is offered to the environment during a time interval, while in [16] actions are available only at a given point of time. ....

....to study a wider and richer range of properties over the processes of the language. In the last years there have been several proposals for the inclusion of timed information in Lotos (e.g. 16, 11, 12] using different approaches to introduce time; for example, in [12] the improved version of [11]) an operator similar to that in [23] is used, denoting that an action is offered to the environment during a time interval, while in [16] actions are available only at a given point of time. Moreover, these formalisms have been assessed in the specifications of a timed protocol [13, 18] These ....

G. Leduc and L. L'eonard. A timed LOTOS supporting a dense time domain and including new timed operators. In Formal Description Techniques V, pages 87--102, 1992.

....and should be added if possible; 3. Regarding real time aspects, ECSs must be kept simple in order to meet certification requirements. It is therefore likely that the real time aspects can easily be expressed using timed process algebras such as ATP [NS91, NS94] or timed versions of Lotos [BL91, LL92, QFA93] Although the objectives of the FLAIR study were probably too ambitious for the current state of the art in formal methods, the authors still believe that the FLAIR principles are sound: formal methods, verification techniques, and automatic code generation could be profitably introduced ....

Guy Leduc and Luc L'eonard. A Timed LOTOS Supporting a Dense Time Domain and Including New Timed Operators. In Michel Diaz and Roland Groz, editors, Proceedings of the 5th International Conference on Formal Description Techniques FORTE'92 (Lannion, France), pages 99--114. IFIP, October 1992.

....of the basic semantic rules, to study their relationships, as well as to propose, at some stage, alternative ways to express a particular feature. Initial inspiration for this work came from an in depth analysis of the temporal extension proposed by G. Leduc, namely Timed LOTOS as presented in [LL92], as well as of the one proposed by T. Bolognesi, namely T LOTOS as presented in [BL92] In particular, the debate between Timed LOTOS and T LOTOS has generated a discussion on whether or not observable actions are to be urgent. In [CdCS93] we proposed our own temporal extension of basic LOTOS, ....

....(and consequently a;bf0g;stop 6 iftg;a;bf0g;stop) as action a s in a;stop cannot be simulated by any action sequence of iftg;a;stop. 5 Conclusion Starting from an earlier experience with the design of RT LOTOS [CdCS93] and taking into account the proposals of G. Leduc, namely Timed LOTOS [LL92] and ET LOTOS [LL93b] three main contributions have been provided in the paper: 1. the definition of the latency operator 2. the proposal of different alternatives for expressing temporal exception handling 3. the definition of a weak equivalence for the basic model with time nondeterminism, ....

G. Leduc and L. L'eonard. A timed LOTOS supporting a dense time domain and including new timed operators. In Proc. Fifth Intern. Confer. on Formal Description Techniques (FORTE), Lannion, France, October 1992.

.... quantitative time requirements [BL92, LL93] Although it is not the main purpose of this paper to compare RT LOTOS with other proposals made within the LOTOS community, it is worth noting that the initial inspiration of RT LOTOS [CdCS93] came from an in depth analysis of both Timed LOTOS [LL92] and T LOTOS [BL92] Several assumptions and decisions made during the design of RT LOTOS have then been taken in order to preserve as much convergence as possible with the successor of Timed LOTOS, namely ETLOTOS [LL93] As a consequence, RT LOTOS and ET LOTOS feature several points in common ....

G. Leduc and L. L'eonard. A timed LOTOS supporting a dense time domain and including new timed operators. In Proc. 5th Intern. Confer. on Formal Description Techniques (FORTE'92), Lannion, France, October 1992.

....one. Although we could also have defined such a new operator ourselves we have not done so because adding new real time operators increases the complexity of the semantics and can have subtle, unanticipated side effects. For instance, when a delay operator is added to an algebra like LOTOS [16], we note that it can interact with other operators in unfortunate ways. If such a delay is used as the second operand to the LOTOS disabling operator then the combined behaviour no longer enjoys the simple recursive definition normally possible by unwinding the disabling operator as a choice ....

G. Leduc and L. L'eonard. A timed LOTOS supporting a dense time domain and including new timed operators. In M. Diaz and R. Groz, editors, Formal Description Techniques, V, pages 87--102. North-Holland, 1992.

....has been thoroughly studied. A sign of the interest of the work we present here is that ET LOTOS has been retained as the basis of the timed extension of LOTOS currently developed in the ISO#IEC JTC1#SC33 standardization committee [ISO98] ET LOTOS is an extended and improved version of [LeL93, Le # L94] In particular, the language presented in [Le # L94] has been enhanced and slightly modified to cover full LOTOS (i.e. LOTOS with data types) Among the other proposals that have inspired us, let us mention Real Time CSP [ReR88] TCCS [MoT90] and the Calculus of Real Time Systems ....

....in the semantics. Basically, in rule (H3) P## can be seen as a boolean function which must be verified on the domain [0, d ) However, computations of the same complexity must still be performed in the presence of the reverse persistency. A comparison with earlier proposals, like [LeL93] can be found in that paper. For example, hide g in g#t[SP(t) P# requires to verify that SP(t) is never true on [0, d ) It is not more complex than verifying that hide g in g x : s[SP#(x) P# , i.e. that SP#(x) is never true on #(s) In fact, such a level of complexity cannot be ....

Leduc, G., Le # onard, L. : A timed LOTOS supporting a dense time domain and including new timed operators. In : M. Diaz, R. Groz, eds., Formal Description Techniques, V. NorthHolland, Amsterdam, 1993, 87--102.

....is used to model many relevant systems. For completeness, we also provide an additional example of a token bucket al..gorithm in [Le # L98] In this paper we present the theoretical aspects of ET LOTOS and the detailed study of its semantics. ET LOTOS is an extended and improved version of [LeL93, Le # L94] In particular, the language presented in [Le # L94] has been enhanced and slightly modified to cover full LOTOS (i.e. LOTOS with data types) It is the basis of the timed extension of LOTOS currently developed in the ISO#IEC JTC1#SC33 standardization committee [ISO98] It has been ....

Leduc, G. and Le # onard, L. : A timed LOTOS supporting a dense time domain and including new timed operators. In : M. Diaz, R. Groz, eds., Formal Description Techniques, V, North-Holland, Amsterdam, 1993, 87--102.

....appear regularly. This situation reflects the diversity of the philosophies envisaged about the way time should be introduced in the FDTs, and the variety of the options explored in order to realize them. An overview and synthesis may be found in [NiS 92] a classification is also proposed in [LeL 93] But questions thus arise: are all the choices equally valuable What are the advantages and disadvantages of each one What are the improvements a given formalism would require We think that the most instructive way to get pieces of answers to these questions is simply to try to apply these ....

G. Leduc, L. Lonard, A timed LOTOS supporting a dense time domain and including new timed operators. in: M.Diaz, R.Groz eds., Formal Description Techniques V, (North-Holland, Amsterdam, 1993), 87-102.

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G. Leduc, L. Lonard, A timed LOTOS supporting a dense time domain and including new timed operators, in: M. Diaz, R. Groz, eds., Formal Description Techniques, V (North-Holland, Amsterdam, 1993) 87-102.

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G. Leduc and L. L'eonard. A timed lotos supporting dense time domain and including new timed operators. Formal Description Techniques, V:87--182, 1993.

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