S. Andler. Predicate path expressions. Proceedings 6-th ACM Symposium on Principles of Programming Languages, pages 226--236, Jan. 1979.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....I 2 ; Delta Delta Delta ; I n ) provides a set of services through interfaces I 1 ; I 2 ; I n . Any accesses or modifications to the data structures of M must be made through the interfaces. Examples of structured approaches are Monitor [Hoa74] abstract data types with Path Expressions [CH74, And79] or abstract expressions [AHV85] 21 Mediators [GC86] rendezvous based models [Geh84, GR86] remote procedure call models [BN84] and concurrent object oriented models [Ame87, YBS87, TS89, CK92, WKH92] There are two possible sources of concurrency and interactions among programs in such ....

S. Andler. Predicate Path Expression. In Proc. Sixth ACM Symposium on Principles of Programming Languages, pages 226--236, 1979.

....EVENT SPECIFICATION EXTENSIONS We have limited ourselves in the preceding to events that can be monitored efficiently by means of finite automata. But there are other composite events of interest that we may be able to capture efficiently as well. In particular, as in the case of path expressions [2, 6], we discuss here the notion of (unbounded) event counters. The term #F is used to mean the number of times event F has occurred. An event point can be specified using event equations. For example, #E #F 5) 0 occurs at any history point if the equation holds at that point. An event ....

S. Andler, "Predicate Path Expressions", Proceedings of the 6th ACM Symposium on Principles of Programming Languages, 1979, 226-236.

....simultaneous, and alternative occurrences of processes, and process iteration. This proposal builds on work by Chittaro and Montanari [10] on modeling discrete processes. The set of constructors of the current version of the Macro Event Calculus is similar to the path expression operators of [3]. Originally developed for modeling operating system behavior, path expressions have been successfully used in several areas of Computer Science. In this paper, we show how their formalization within the Event Calculus can be usefully 47 Main Gas Safety disable Lighter Power Desired ....

....T . This de nition formalizes the core of the notion of process studied at length in [10, 22] which in turn extends the limited notion of macro events (essentially delayed sequencing) presented in [12] The constructors we included in this language are based on the path expression operators of [3] and on the process calculi operators found in [15, 21] Observe that a number of useful constructs are easily expressible with the language in De nition 4.1. In particular sequencing with arbitrary delay ( immediate sequencing ( non empty iteration ( and xed length iteration ( n ....

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S. Andler. Predicate path expressions. In Proceedings of the 6th ACM Symposium on Principles of Programming Languages, 1979.

....for the server. The object expression repeats the Methods, Path and Ordering sections of the Server 1. An invokes method is only usually declared if the object will invoke the method in an unqualified fashion. 2. It was originally intended that APOSTLE would support predicate path expressions [Andler 79] however time did not allow us to implement them. 42 Object type (as it is going to deliver objects that implement the Server type) but adds a state section to provide an implementation of the job method. The job method simply does a wait for the service time of the job. The Path section ....

....mutual exclusion locks, etc. with monitor objects [Andrews 91] and if a regular object is used the resource acquisition object can be coded using these. A more desirable solution would be to allow concurrency control to be expressed declaratively using predicate path expressions (PPEs) Andler 79] or enabled sets [Tomlinson 89] for example. This is clearly superior to embedding concurrency control information into the get and put methods. 8.2 Modelling preemption MODSIM II models preemption by providing interruptible waits. Section 3.4.2 showed how these could be emulated in APOSTLE ....

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S. Andler, "Predicate Path Expressions", Proc. 6th ACM Symp. on the Principles of Programming Languages, San Antonio, Texas, 29-31 January 1979, pp. 226-236.

....M = I 1 ; I 2 ; 1 1 1 ; I n ) provides a set of services through interfaces I 1 ; I 2 ; I n . Any accesses or modifications to the data structures of M must be made through the interfaces. Examples of structured approaches are Monitor [Hoa74] abstract data types with Path Expressions [CH74, And79] or abstract expressions [AHV85] Mediators [GC86] rendezvous based models [Geh84, GR86] remote procedure call models [BN84] and concurrent object oriented models [Ame87, YBS87, TS89, CK92, WKH92] There are two possible sources of concurrency and interactions among programs in such models: ....

S. Andler. Predicate Path Expression. In Proc. Sixth ACM Symposium on Principles of Programming Languages, pages 226--236, 1979.

....to execute an operation on an object is permitted to continue. Several languages employ the concept of guards, in one form or another, in their synchronisation mechanisms: CSP [15] Synchronising Resources (SR) 4] Ada [1] Guide [10] Mediators [13] DRAGOON [12] and Predicate Path Expressions [2] are the best known examples. Scheduling predicates improve upon these previous mechanisms by having more expressively powerful guards. 1.2 Structure of Report This report is structured as follows: Section 2 presents a brief overview of the different object models which can be commonly found in ....

....In this generalised form, this formula looks unwieldy. For a concrete example of this with n = 2, the reader is referred back to the Shortest Job Next scheduler with FIFO sub ordering, as shown in Figure 4. 7. 3 Path Expressions It has been shown elsewhere [16] that Predicate Path Expressions [2] can be implemented in terms of synchronisation counters. Since we have already shown in Section 7.1 that synchronisation counters are simply a restricted form of scheduling predicates, it follows that Predicate Path Expressions are also subsumed by scheduling predicates. 8 Efficient ....

Sten Andler. Predicate Path Expressions. In Sixth Annual ACM Symposium on Principles of Programming Languages, pages 226--236, San Antonio, Texas, 1979.

....an operation s behavior, particularly, its synchronization condition. Rather than specifying the processes, a data oriented model describes the data in a system and how operations on the data behave. Specifications using data oriented models, such as LTAM [Lamport 89] Predicate Path Expressions [Andler 79] and the Actors Model [Agha 86, Agha Hewitt 87] localize the synchronization conditions for individual objects or operations. However, like the process models, these do not scale well; they provide a semantic model rather than a specification language. Instead of specifying systems directly in ....

Sten Andler. Predicate Path Expressions. In Sixth Annual ACM Symposium on Principles of Programming Languages, pages 226-236. San Antonio, TX, 1979.

....the total number of invocations for each operation of the object that have actually arrived at the object, have started execution and have terminated execution, etc. Synchronisation counters are quite common and can be found in numerous synchronisation mechanisms [DDR 91] MWBD91] CGM91] And79] GW91] Cou94] Usually, there are five counters for each operation of an object. These are: 1 arrival(Op) total number of invocations to execute operation Op that have arrived at this object. wait(Op) current number of invocations that are waiting to execute Op. start(Op) total number of ....

....If A is a read style operation and B is a write style operation then it is clear that the above path expression implements the basic readers writer policy. The basic Path Expressions mechanism has spawned a number of variations including Open Path Expressions [CK80] and Predicate Path Expressions [And79] 1.5 Eiffelk In the Eiffelk language [Car93] objects are either process or passive. Passive objects are local to the process object in which they were created. Process objects have their own thread which both schedules pending invocations and services them. There is no concurrency within a ....

Sten Andler. Predicate Path Expressions. In Sixth Annual ACM Symposium on Principles of Programming Languages, pages 226--236, San Antonio, Texas, 1979.

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S. Andler. Predicate path expressions. Proceedings 6-th ACM Symposium on Principles of Programming Languages, pages 226--236, Jan. 1979.

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