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1.
This paper presents a new model for passing messages in communicating stream X-machine systems (CSXMS). The components are
stream X-machines with ε-transitions, acting simultaneously. The states are partitioned into processing and communicating
states. Passing messages between the X-machines involves only communicating states. A communication matrix is used as a common
memory. It is shown that a structured way of using channels, namely via select constructs with guarded alternatives and terminate clause, may be implemented. An automatic scheme for writing concurrent programs in an Ada-like style, starting from a CSXMS,
is proposed.
Received December 1999 / Accepted in revised form January 2001 相似文献
2.
Stream X-machines have been used in order to specify a range of systems. One of the strengths of this approach is that, under
certain well-defined conditions, it is possible to produce a finite test that is guaranteed to determine the correctness of
the implementation under test (IUT). Initially only deterministic stream X-machines were considered in the literature. This
is largely because the standard test algorithm relies on the stream X-machine being deterministic.
More recently the problem of testing to determine whether the IUT is equivalent to a non-deterministic stream X-machine specification has been tackled. Since non-determinism can be important for specifications,
this is an extremely useful extension. In many cases, however, we wish to test for a weaker notion of correctness called conformance. This paper considers a particular form of non-determinism, within stream X-machines, that will be called quasi-non-determinism.
It then investigates the generation of tests that are guaranteed to determine whether the IUT conforms to a quasi-non-deterministic stream X-machine specification. The test generation algorithm given is a generalisation of that
used for testing from a deterministic stream X-machine.
Received November 1999 / Accepted in revised form December 2000 相似文献
3.
Marian Gheorghe 《Formal Aspects of Computing》2000,12(6):459-472
Stream X-machines are a general and powerful computational model. By coupling the control structure of a stream X-machine
with a set of formal grammars a new machine called a generalised stream X-machine with underlying distributed grammars, acting as a translator, is obtained. By introducing this new mechanism a hierarchy of computational models is provided.
If the grammars are of a particular class, say regular or context-free, then finite sets are translated into finite sets,
when ?k, = k derivation strategies are used, and regular or context-free sets, respectively, are obtained for ?k, * and terminal derivation strategies. In both cases, regular or context-free grammars, the regular sets are translated into non-context-free
languages. Moreover, any language accepted by a Turing machine may be written as a translation of a regular set performed
by a generalised stream X-machine with underlying distributed grammars based on context-free rules, under = k derivation strategy. On the other hand the languages generated by some classes of cooperating distributed grammar systems
may be obtained as images of regular sets through some X-machines with underlying distributed grammars. Other relations of
the families of languages computed by generalised stream X-machines with the families of languages generated by cooperating
distributed grammar systems are established. At the end, an example dealing with the specification of a scanner system illustrates
the use of the introduced mechanism as a formal specification model.
Received September 1999 / Accepted in revised form October 2000 相似文献
4.
Tudor Bălănescu 《Formal Aspects of Computing》2000,12(6):473-484
Some conditions relating to the automata involved in the W-testing method are discussed. It is also shown how to use the
method for reduced automata instead of minimal automata. New design test conditions (weak output distinguishable, strong test-complete and output delimited type) are considered for the generalised stream X-machines (stream X-machines with basic functions replaced by relations and having as output strings of symbols rather than single
symbols). It is proved that testing methods similar to those already developed for ordinary deterministic stream X-machines
may be applied for generalised stream X-machines with output delimited types. A particular case of generalised stream X-machine
with output delimited type is the X-machine with output delimiter, which produces outputs having a distinct right end character.
Received October 2000 / Accepted in revised form January 2001 相似文献
5.
X-machines were proposed by Holcombe as a possible specification language and since then a number of further investigations
have demonstrated that the model is intuitive and easy to use as well as general enough to cater for a wide range of applications.
In particular (generalised) stream X-machines have been found to be extremely useful as a specification method and most of
the theory developed so far has concentrated on this particular class of X-machines. Furthermore, a method for testing systems
specified by stream X-machines exists and is proved to detect all faults of the implementation provided that the system meets
certain initial requirements. However, this method can only be used to generate test sequences from deterministic X-machine
specifications. In this paper we present the theoretical basis for a method for generating test sets from non-deterministic
generalised stream X-machines.
Received November 1999 / Accepted in revised form September 2000 相似文献
6.
针对在XML文档树模型中进行后兄弟节点查询时内存消耗大、匹配效率低等缺陷,提出一种基于XML数据流与栈的后兄弟查询算法。采用SAX解析器与结构连接方法,对XML文档中所有已知节点与后兄弟节点进行精确匹配并输出。结果表明,该算法具有适用范围广、占用系统资源少、匹配效率高等优势。 相似文献
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