摘要:

The field of software metrication can be divided between those program measurement techniques that are largely textual (e.g. the metrics of Halstead and his followers) and those that are more structural, i.e. based on thehierarchicaldecomposition structure of the underlying flow graph. We are concerned with the latter, but only from the ‘control flow’ perspective. (Note that structural metrics may also focus on the ‘data flow’ model, especially when attempting to measure module cohesion and coupling, but these are not of concern here.) The decomposition is of two varieties;sequenceandnesting, each extended recursively to the bottom-most level consisting of ‘prime flow graphs’, those that cannot be constructed from the sequence and nesting operations. These then play a role in the software metric theory not unlike that of prime numbers in arithmetic. We initiate a new method for generating the prime flow graphs, based more firmly on graph-theoretic techniques and classical enumeration theory than in previous work. The technique is rooted in a fundamental reformulation of the flow graph model itself, making use of the notation of a cubic graph. This approach offers new insights into the decompositional methodology and broad implications for the design of effective structural metrics based on that methodology. In particular, we are able to obtain wide-ranging software engineering applications, towards the comparison of individual hierarchical metrics, the generation and enumeration of the prime flow graphs, and the design of a test for flow graph primality.

DOI:10.1049/sej.1993.0030

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Software maintenance is an important area in practical software engineering that has been largely overlooked by many theoretical computer scientists. This paper gives an overview of formal techniques developed recently to aid the software maintenance process, and in particular reverse engineering and re-engineering. In the future, it is suggested that specifications, rather than programs, should be maintained. The described work provides a mathematical basis for a large collaborative project, which has also been investigating many other aspects of software maintenance.

DOI:10.1049/sej.1993.0031

出版商:IEE    

年代:1993

数据来源: IET

摘要:

We present a new framework integrating diverse aspects of cognitive complexity. Methods based on communication theory are used to compute a reasonable measurement of comprehensibility integrating the contribution of diverse aspects, such as control flow, data flow, modularity or even compliance with standards, in a single value. In contrast to most published metrics, our approach is based on document/programmer interaction, rather than on document structure. We model this interaction by an abstract noisy communication channel, where perturbations stemming from decoding errors are used for complexity quantification. This new approach conforms with approved programming heuristics as well as with empirical results.

DOI:10.1049/sej.1993.0032

出版商:IEE    

年代:1993

数据来源: IET

摘要:

It is becoming widely accepted that along with the formal specification of functional properties it is necessary, in some systems, to provide a specification of timeliness properties. Unfortunately, the main methods which seem to provide this form of requirement appear to be based solely on a global model of time, which we hold to be inappropriate for the specification of asynchronous distributed systems. This paper introduces a set of definitions for the Z specification language which enables timeliness properties to be represented formally. The toolkit provides a method of framing the temporal specifications, which enables these specifications to be looked at from multiple viewpoints; a feature which allows us to look at the time domain at different levels of abstraction, and to represent the effects of multiple unsynchronised clocks. A formal basis for the toolkit is given, together with justification for the features of the model of time that has been adopted.

DOI:10.1049/sej.1993.0033

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The paper presents exact schedulability analyses for real-time systems scheduled at runtime with a static priority pre-emptive dispatcher. The tasks to be scheduled are allowed to experience internal blocking (from other tasks with which they share resources) and (with certain restrictions) to release jitter, such as waiting for a message to arrive. The analysis presented is more general than that previously published and subsumes, for example, techniques based on the Rate Monotonic approach. In addition to presenting the relevant theory, an existing avionics case study is described and analysed. The predictions that follow from this analysis are seen to be in close agreement with the behaviour exhibited during simulation studies.

DOI:10.1049/sej.1993.0034

出版商:IEE    

年代:1993

数据来源: IET