A trajectory-based strict semantics for program slicing

We define a program semantics that is preserved by dependence-based slicing algorithms. It is a natural extension, to non-terminating programs, of the semantics introduced by Weiser (which only considered terminating ones) and, as such, is an accurate characterisation of the semantic relationship between a program and the slice produced by these algorithms.Unlike other approaches, apart from Weiser’s original one, it is based on strict standard semantics which models the ‘normal’ execution of programs on a von Neumann machine and, thus, has the advantage of being intuitive. This is essential since one of the main applications of slicing is program comprehension. Although our semantics handles non-termination, it is defined wholly in terms of finite trajectories, without having to resort to complex, counter-intuitive, non-standard models of computation. As well as being simpler, unlike other approaches to this problem, our semantics is substitutive. Substitutivity is an important property because it greatly enhances the ability to reason about correctness of meaning-preserving program transformations such as slicing.     

A web-based topology optimization program

The paper presents a web-based interface for a topology optimization program. The program is accessible over the World Wide Web at the address http://www.topopt.dtu.dk. The paper discusses implementation issues and educational aspects as well as statistics and experience with the program. Received September 29, 2000     

Polymorphic scenario-based specification models: semantics and applications

We present polymorphic scenarios, a generalization of a UML2-compliant variant of Damm and Harel??s live sequence charts (LSC) in the context of object-orientation. Polymorphic scenarios are visualized using (modal) sequence diagrams where lifelines may represent classes and interfaces rather than concrete objects. Their semantics takes advantage of inheritance and interface realization to allow the specification of most expressive, succinct, and reusable universal and existential inter-object scenarios for object-oriented system models. We motivate the use of polymorphic scenarios, formally define their trace-based semantics, and present their application for scenario-based testing and execution, as implemented in the S2A compiler developed at the Weizmann Institute of Science. We further discuss advanced semantic issues arising from the use of scenarios in a polymorphic setting, suggest possible extensions, present a UML profile to support polymorphic scenarios, consider the application of the polymorphic semantics to other variants of scenario-based specification languages, and position our work in the broader context of behavioral subtyping.     

A non-standard semantics for program slicing and dependence analysis

We introduce a new non-strict semantics for a simple while language. We demonstrate that this semantics allows us to give a denotational definition of variable dependence and neededness, which is consistent with program slicing. Unlike other semantics used in variable dependence, our semantics is substitutive. We prove that our semantics is preserved by traditional slicing algorithms.     

The graph topology for linear plants with applications to nonlinearrobust stabilization

The graph topology is defined for the set of finite-dimensional linear time-varying plants that are internally stabilizable by output feedback. This follows some earlier results of M. Vidyasagar et al. (1982) on time-invariant systems. Feedback connections of linear time-varying plants and general nonlinear time-varying controllers are considered, and it is shown that the graph topology is the weakest topology in which feedback stabilization is a robust property. Using this result, necessary and sufficient conditions for robust stabilizability of families of linear time-varying plants with parametric uncertainty are derived     

Mixed projection- and density-based topology optimization with applications to structural assemblies

Structural and Multidisciplinary Optimization - In this paper, we present a mixed projection- and density-based topology optimization approach. The aim is to combine the benefits of both...     

From algebraic semantics to denotational semantics for Verilog

This paper considers how the algebraic semantics for Verilog relates with its denotational semantics. Our approach is to derive the denotational semantics from the algebraic semantics. We first present the algebraic laws for Verilog. Every program can be expressed as a guarded choice that can model the execution of a program. In order to investigate the parallel expansion laws, a sequence is introduced, indicating which instantaneous action is due to which exact parallel component. A head normal form is defined for each program by using a locality sequence. We provide a strategy for deriving the denotational semantics based on head normal form. Using this strategy, the denotational semantics for every program can be calculated. Program equivalence can also be explored by using the derived denotational semantics. A short version of this paper appeared in Proc. ICECCS 2006: 11th IEEE International Conference on Engineering of Complex Computer Systems [48]. This work is partially supported by the National Basic Research Program of China (No. 2005CB321904), the National High Technology Research and Development Program of China (No. 2007AA010302) and the National Natural Science Foundation of China (No. 90718004). Jonathan Bowen is a visiting professor at King’s College London and an emeritus professor at London South Bank University.     

Projective topology on bifinite domains and applications

We revisit extension results from continuous valuations to Radon measures for bifinite domains. In the framework of bifinite domains, the Prokhorov theorem (existence of projective limits of Radon measures) appears as a natural tool, and helps building a bridge between Measure theory and Domain theory. The study we present also fills a gap in the literature concerning the coincidence between projective and Lawson topology for bifinite domains. Motivated by probabilistic considerations, we study the extension of measures in order to define Borel measures on the space of maximal elements of a bifinite domain.     

A metalogic programming approach: language,semantics and applications

Abstract

This paper presents a logic programming language of novel conception, called Reflective Prolog, which allows declarative metaknowledge representation and metareasoning. The language is defined by augmenting pure Prolog (Horn clauses) with capabilities of self-reference and logical reflection. Self-reference is designed as a quotation device (a carefully defined naming relation) which allows the construction of metalevel terms that refer to object-level terms and atoms. Logical reflection is designed as an unquotation mechanism (a distinguished truth predicate) which relates names to what is named, thus extending the meaning of domain predicates. The reflection mechanism is embodied in an extended resolution procedure which automatically switches the context between levels. This implicit reflection relieves the programmer from having to explicitly deal with control aspects of the inference process. The declarative semantics of a Reflective Prolog definite program P is provided in terms of the least reflective Herbrand model of P, characterized by means of a suitable mapping defined over the Herbrand interpretations of P. The extended resolution is proved sound and complete with respect to the least reflective Herbrand model. By illustrating Reflective Prolog solutions to an organic set of problems, and by discussing the main differences with respect to other approaches to logic metaprogramming, we show that the proposed language deploys, within its field of action, greater expressive and inferential power than those available till now. The interpreter of the language has been fully implemented. Because of its enhanced power, logic semantics and working interpreter, Reflective Prolog is offered as a contribution toward making the declarative approach of logic programming applicable to the development of increasingly sophisticated knowledge-based systems.     

Cellular topology and its applications in image processing

In this paper the interaction between Minkowski algebra, nondiscrete cellular topologies and some well known basic cellular image processing operations is investigated. It is shown that some useful topological measures can be extracted from these basic image operations and that these operations can be viewed from a nonalgebraic and purely topological point of view.     

UpStream: storage-centric load management for streaming applications with update semantics

This paper addresses the problem of minimizing the staleness of query results for streaming applications with update semantics under overload conditions. Staleness is a measure of how out-of-date the results are compared with the latest data arriving on the input. Real-time streaming applications are subject to overload due to unpredictably increasing data rates, while in many of them, we observe that data streams and queries in fact exhibit “update semantics” (i.e., the latest input data are all that really matters when producing a query result). Under such semantics, overload will cause staleness to build up. The key to avoid this is to exploit the update semantics of applications as early as possible in the processing pipeline. In this paper, we propose UpStream, a storage-centric framework for load management over streaming applications with update semantics. We first describe how we model streams and queries that possess the update semantics, providing definitions for correctness and staleness for the query results. Then, we show how staleness can be minimized based on intelligent update key scheduling techniques applied at the queue level, while preserving the correctness of the results, even for complex queries that involve sliding windows. UpStream is based on the simple idea of applying the updates in place, yet with great returns in terms of lowering staleness and memory consumption, as we also experimentally verify on the Borealis system.     

Algebraic semantics for natural language: some philosophy, some applications

Information processing, when performed by an intelligent agent, draws on a wide array of knowledge sources. Among them are world knowledge, situation knowledge, conceptual knowledge and linguistic knowledge. The focus in this paper will be on the semantic knowledge which is part of the general linguistic competence of any speaker of a natural language (NL).In particular, this knowledge contains ways of organizing the linguistic ontology, i.e. the collection of heterogeneous entities that make up the domain of discourse. The representation language that is proposed here to model this knowledge stresses the structural properties of the ontology. This approach has been persued under the name of algebraic semantics.The paper starts out by explaining the term "algebraic semantics" as it is used in logic. Two senses of "algebraic" are distinguished that are called here "conceptual" and "structural". These two senses of the algebraic method are then applied to NL semantics. The conceptual part is realized by the method of structuring the domains of linguistic ontology in various ways. Thus plural entities are recognized along with mass entities and events. The common outlook here is mereological or lattice-theoretical. Some applications to the study of plurals are given that are to show the usefulness of the algebraic approach. Finally, the ontology of plurals is addressed, and comments are made on some relevant discussion of mereology in recent philosophical work. In sum, it is contended that the algebraic perspective while being of interest in semantics and philosophy proper, also fits both the spirit and the practice of much work that has been done in the Artificial Intelligence (AI) field of knowledge representation.     

Some applications of small gain theorem to interconnected systems

Based on small gain theorem, decentralized control of interconnected systems is studied. Linear matrix inequality conditions are given for stabilizability of interconnected systems. Interconnections can be used to improve system robustness in the sense of small gain theorem. An example is given to illustrate the results. Finally, interconnected systems composed of symmetric subsystems are studied.     

Some applications of resultants to problems in computational geometry

Resultants were originally developed in the 18th and 19th centuries to solve certain simple algebraic problems. Here we shall present some applications of resultants to several important problems in computational geometry, including the implicitization, inversion, and intersection of parametric rational polynomial curves and surfaces.This paper was first delivered orally at the International Conference on Engineering and Computer Graphics in Beijing, China, held in August 1984     

Some applications of resultants to problems in computational geometry

Resultants were originally developed in the 18th and 19th centuries to solve certain simple algebraic problems. Here we shall present some applications of resultants to several important problems in computational geometry, including the implicitization, inversion, and intersection of parametric rational polynomial curves and surfaces.     

Attributing semantics to personal photographs

A major bottleneck for the efficient management of personal photographic collections is the large gap between low-level image features and high-level semantic contents of images. This paper proposes and evaluates two methodologies for making appropriate (re)use of natural language photographic annotations for extracting references to people, location and objects and propagating any location references encountered to previously unannotated images. The evaluation identifies the strengths of each approach and shows extraction and propagation results with promising accuracy.

Bringing semantics to Web services

A key element to realizing the Semantic Web is developing a suitably rich language for encoding and describing Web content. Such a language must have a well defined semantics, be sufficiently expressive to describe the complex interrelationships and constraints between Web objects, and be amenable to automated manipulation and reasoning with acceptable limits on time and resource requirements. A key component of the Semantic Web services vision is the creation of a language for describing Web services. DAML-S is such a language it is a DAML+OIL ontology for describing Web services that a coalition of researchers created with support from DARPA.