23372292
A Calculus for Schemas in Z
The popularity and flexibility of the Z notation can largely be attributed to its notion of schemas. We describe these schemas and illustrate their various common uses in Z. We also present a collection of logical laws for manipulating these schemas. These laws are capable of supporting reasoning about the Z schema calculus in its full generality. This is demonstrated by presenting some theorems about the removability of schemas from Z specifications, together with outline proofs. We survey briefly models against which this logical system may be proven sound, and other related logics for Z.
6469757
Teaching Formal Methods in Context
The Software Engineering Programme at Oxford teaches formal methods as an integral part of its programme of professional education in software engineering. This paper explains how the methods are taught—in the context of emerging trends in software development, and in the context of existing practice—and how their use is promoted through course design and motivating examples.
14174107
Lifting in Z
Formal notations such as Z provide powerful support for writing clear specifications, and for undertaking proofs of properties of those specifications. In this paper, we explore one particular style of specification, with applications in control theory and real-time specification. The notation we define permits the accurate description of concepts in these fields without significant overhead or notational clutter. This notation has long been used by practitioners in these fields; we demonstrate that it may be defined within Draft Standard Z, and that the resulting specifications are amenable to proof.
265154
A Set-Theoretic Model for Real-Time Specification and Reasoning
Timed-trace formalisms have emerged as a powerful method for specifying and reasoning about concurrent real-time systems. We present a simple variant which builds methodically on set theory, and is thus suitable for use by programmers with little formal methods experience.
14876206
E-science experiences: software engineering practice and the EU DataGrid
The conduct of collaborative scientific study mediated by the internet -e-science - is giving rise to a new type of large distributed software project. This paper reports initial experiences of one such project: the European DataGrid. We record observations about the intended lifecycle and process, compared with actual practice. The paper explores the applicability of current software development practices from academic, commercial, and open source sectors in the context of such Grid projects.
34718551
Encoding W: A Logic for Z in 2OBJ
A prototype proof system for “\(\mathcal{W}\): A Logic for Z” has been produced using the 2OBJ metalogical theorem-prover. 2OBJ permits an encoding which is very similar in structure to that of \(\mathcal{W}\), and the details are presented here. Like \(\mathcal{W}\)the encoding assumes that all its inputs are well-typed. The structure of the encoding is enhanced by a meta-rule on the lifting of proof rules and tactics. There is some discussion of how tactics can make \(\mathcal{W}\)more easily usable.
5189033
Routing in grid graphs by cutting planes
In this paper we study the following problem, which we call the weighted routing problem. Let be given a graphG = (V, E) with non-negative edge weightswe ∈ ℝ+ and letN,N ≥ 1, be a list of node sets. The weighted routing problem consists in finding mutually disjoint edge setsS1,...,SN such that, for eachk ∈ {1, ...,N}, the subgraph (V(Sk),Sk) contains an [s, t]-path for alls, t ∈ Tk and the sum of the weights of the edge sets is minimal. Our motivation for studying this problem arises from the routing problem in VLSI-design, where given sets of points have to be connected by wires. We consider the weighted routing problem from a polyhedral point of view. We define an appropriate polyhedron and try to (partially) describe this polyhedron by means of inequalities. We describe our separation algorithms for some of the presented classes of inequalities. Based on these separation routines we have implemented a branch and cut algorithm. Our algorithm is applicable to an important subclass of routing problems arising in VLSI-design, namely to switchbox routing problems where the underlying graph is a grid graph and the list of node sets is located on the outer face of the grid. We report on our computational experience with this class of problem instances.
16635941
Packing Steiner trees: a cutting plane algorithm and computational results
In this paper we describe a cutting plane algorithm for the Steiner tree packing problem. We use our algorithm to solve some switchbox routing problems of VLSI-design and report on our computational experience. This includes a brief discussion of separation algorithms, a new LP-based primal heuristic and implementation details. The paper is based on the polyhedral theory for the Steiner tree packing polyhedron developed in our companion paper (this issue) and meant to turn this theory into an algorithmic tool for the solution of practical problems.
10076896
Agent Assistance for 3D World Navigation
This paper presents mechanisms and approaches to assist user navigation and exploration within 3-dimensional worlds. Specifically, we advocate the deployment of an agent based approach for dynamic system assistance and intervention. An algorithm has been developed, that produces a performance measure, which is employed by the intelligent agent to activate system interventions. We outline the importance of providing discrete navigational cues to users in order to increase their sense of immersion and their overall satisfaction while working within the 3D world. We present HADES - the Home of the Adaptive Environmental System, which is a 3-dimensional world within which the intelligent agent is immersed. The agent therefore has the ability to transform this 3D world into an intelligent environment. HADES reacts proactively to users' movements and offers navigational help indirectly. Indirect navigational support increases the user's satisfaction with his own performance and therefore endorses the user's sense of immersion.
14479325
Bus catcher: a context sensitive prototype system for public transportation users
In this paper we describe the architectural andfunctional characteristics of Bus Catcher, a contextsensitive prototype system for public transportation users.Bus Catcher assists mobile users in planning their busrides by providing timely and accurate information aboutcurrent bus locations and estimated arrival times. Acomplete report on the implementation together with apreliminary evaluation of the system is provided in thispaper.
16348358
Agent Chameleons: Virtual Agents Real Intelligence
Agent Chameleons provides virtual agents powered by real intelligence, delivering next generation autonomic entities that can seamlessly migrate, mutate and evolve on their journey between and within physical and digital information spaces.