System specifications are a series of statements that spell out the requirements of the system in question. The specifications are said to be consistent if there is an assignment of truth values to the variables in the expressions that makes all the expressions true.
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Proceedings of the 1977 annual conference on - ACM '77
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Lecture notes in electrical engineering
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ACM Transactions on Computational Logic
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Over the past decades, a common definition of the term system has eluded researchers and practitioners alike. We reviewed over 100 current and historical definitions of system in an effort to understand perspectives and to propose the most comprehensive definition of this term. There is much common ground in different families of definition of system, but there are also important and significant differences. Some stem from different belief systems and worldviews, while others are due to a pragmatic desire to establish a clear definition for system within a particular community, disregarding wider considerations. In either case, it limits the effectiveness of various system communities' efforts to communicate, collaborate, and learn from the experience of other communities. We discovered that by considering a wide typology of systems, Bertalanffy's General Systems Theory provides a basis for a general, self-consistent sensible framework, capable of accommodating and showing the relationships amongst the variety of different definitions of and belief systems pertaining to system. Emergence, the appearance of a new phenomenon or capability as a result of relation or interaction between objects, is key in differentiating between objects that are systems and those that are not. Hence we propose a family of definitions, related by the common theme of emergence, which is in line with both the realist and constructivist worldviews, and covers real and conceptual systems. We believe this better reflects the current scope of systems engineering and is required to support the aspirations expressed in INCOSE SE Vision 2025. Motivation There is a need to clarify the meaning and usage of the word system, because current differences in interpretation by individuals and communities are leading to miscommunication. As this term serves different and important purposes, misinterpretations should be avoided, because they can lead to potentially adverse consequences. Our effort is to synthesize a definition, or a family of definitions, which can be shared by all those who use the term system. A well-conceived definition should enable the following objectives: communicate the meaning of system more effectively across communities of research and practice to achieve common goals,
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System requirements define conditions and capabilities to be met by a system under design. They are a partial definition in natural language, with inevitable ambiguities. Formalisation concerns with the transformation of requirements into a specification with unique interpretation, for resolving ambiguities, underspecified references and for assessing whether requirements are consistent, correct (i.e. valid for an acceptable solution) and attainable. Formalisation and validation of system requirements provides early evidence of adequate specification, for reducing the validation tests and high-cost corrective measures in the later system development phases. This article has the following contributions. First, we characterise the specification problem based on an ontology for some domain. Thus, requirements represent a particular system among many possible ones, and their specification takes the form of mapping their concepts to a semantic model of the system. Second, we analyse the state-of-the-art of pattern-based specification languages, which are used to avoid ambiguity. We then discuss the semantic analyses (missing requirements, inconsistencies etc.) supported in such a framework. Third, we survey related research on the derivation of formal properties from requirements, i.e. verifiable specifications that constrain the system’s structure and behaviour. Possible flaws in requirements may render the derived properties unsatisfiable or not realizable. Finally, this article discusses the important challenges for the current requirements analysis tools, towards being adopted in industrial-scale projects.
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Computing Research Repository
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