Task models and problem solving methods can be specified informally or formally. In recent years various approaches have formalized their notion of task model or problem solving method. Most modelling approaches concentrate on the form of a task model or problem solving method rather than on their precise semantics; a formalisation is often only a syntactical formalisation. A more precise definition of the semantics requires explication of the control of a system's behaviour. In this paper temporal semantics is defined for a compositional modelling approach to task models and problem solving methods. The semantics is a description of a compositional system's behaviour; a temporal approach provides a means to describe the dynamics involved. The formalisation of the semantics is based on compositional three-valued temporal models. The compositional structure of information states, transitions and reasoning traces provides a transparant model of the system's behaviour, both conceptually and formally.

The specification and management of requirements is widely considered to be one of the most important yet most problematic phases in software engineering. In some applications, such as in safety critical areas or knowledge-based systems, the construction of a requirements domain theory is regarded as an important part of this phase. Building and maintaining such a domain theory, however, requires a large investment and a range of powerful validation and maintenance tools. The area of `theory refinement' is concerned with the use of training data to automatically change an existing theory so that it better fits the data. Theory refinement techniques have not been extensively used in applications because of the problems in scaling up their underlying algorithms. In this paper we describe an environment for validating and maintaining a requirements domain theory written in a customised form of many-sorted logic. The environment has been used for several years to maintain a theo...

In this paper we describe a tools environment which automates the validation and maintenance of a requirements model written in many-sorted first order logic. We focus on: a translator, that produces an executable form of the model; blame assignment functions, which input batches of mis-classified tests (i.e. training examples) and output likely faulty parts of the model; and a theory reviser, which inputs the faulty parts and examples and outputs suggested revisions to the model. In particular, we concentrate on the problems encountered when applying these tools to a real application: a requirements model containing air traffic control separation standards, operating methods and airspace information. 1. Introduction A unifying theme in the research areas of knowledge engineering, requirements engineering and formal methods is the construction and validation of requirements models represented as formal systems (using languages such as RML [7]). Within the knowledge based system communi...

Acknowledgement I would like to take this opportunity to express my sincere gratitude to those who assisted me, in one way or another, with my Ph.D. in the last four years. First and foremost, I would like to thank my Honor's Year Project and Ph.D. advisor Dr. Dong Jin Song for his never-ending enthusiasm, guidance, support, encouragement and insight throughout the course of my post graduate study. His diligent reading and insightful and constructive criticism of early drafts and many other works made this thesis possible. To my fellow students, Chen Chunqing, Sun Jun and my cousin Feng Yuzhang- your friendship, collaboration and funny chit chat gave me inspiration and helped me go through the long and sometimes not-so-smooth ride of Ph.D. study. To my former lab mates Dr. Sun Jing and Dr. Wang Hai- for your suggestions on all aspects of research works and generous hospitality. I am indebt to Dr. Bimlesh Wadha and Dr. Khoo Siau Cheng for the valuable comments on an early draft of this thesis. Dr. Wadha, in particular, carefully reviewed the entire thesis and corrected many language errors. I am sincerely grateful to her for the time and effort put into this. I am also grateful to the external examiner and many anonymous reviewers who reviewed this thesis and previous publications that are part of this thesis and provided critical comments, which contributed to to the clarification of many of the ideas presented in this thesis.