12466079
ACI1 constraints
Disuniication is the problem of deciding satissability of a system of equations and disequations w.r.t. a given equational theory. In this paper we study the disuni-cation problem in the context of ACI1 equational theories. We provide a characterization of the interpretation structures suitable to model the axioms in ACI1 theories. The satissability problem is solved using known techniques for the equality constraints and novel methodologies to transform disequation constraints into solved forms. We propose three solved forms, ooering an increasingly more precise characterization of the set of solutions. Two of them can be computed and tested in polynomial time. The novel results achieved open new possibilities in the practical and eecient manipulation of ACI1 constraints.
23168836
JSetL: a Java library for supporting declarative programming in Java
18295484
Embedding extensional finite sets in CLP
In this paper we review the definition of {log}1, a logic language with sets, from the viewpoint of CLP. We show that starting with a CLP-scheme allows a more uniform treatment of the built-in set operations (namely, =, ∈ and their negative counterparts), and allows all the theoretical results of CLP to be immediately exploitable. We prove this by precisely defining the privileged interpretation domain and the axioms of the selected set theory. Then we define a non-deterministic procedure for checking constraint satisfiability based on the reduction of a given constraint to a collection of constraint in a suitable canonical form, which is provable to be sound and complete w.r.t. the given theory. Algorithms for trasforming each one of the set constraints the language provides (=, 6=, ∈ and 6∈) into their corresponding canonical forms are described in details. It is also shown that the resulting language is powerful enough to allow all the usual operations on sets (such as ⊆, ∪, etc.) to be effectively programmed in the language itself.
14836519
From Set to Hyperset Unification
In this paper we show how to extend a set unification algorithm— that is, an extended unification algorithm incorporating the axioms of a simple theory of sets—to hyperset unification (roughly speaking, to sets in which membership can form cycles). This result is obtained by enlarging the domain of terms (hence, trees) to that of graphs involving free as well as interpreted function symbols (namely, the set element insertion and the empty set), which can be regarded as a convenient denotation of hypersets. We present a hyperset unification algorithm that (nondeterministically) computes, for each given unification problem, a finite collection of systems of equations in solvable form whose solutions represent a complete set of solutions for the given unification problem. The crucial issue of termination of the algorithm is addressed and solved by the addition of simple nonmembership constraints. Finally, the hyperset unification problem in
3157847
Intensional Sets in CLP
We propose a parametric introduction of intensionally defined sets into any \(CLP(\mathcal \{D\})\) language. The result is a language \(CLP({\mathcal \{D\}})\), where constraints over sets of elements of \(\mathcal D\) and over sets of sets of elements, and so on, can be expressed. The semantics of \(CLP({\mathcal \{D\}})\) is based on the semantics of logic programs with aggregates and the semantics of CLP over sets. We investigate the problem of constraint resolution in \(CLP({\mathcal \{D\}})\) and propose algorithms for constraints simplification.
1003988
Solving Systems of Equations over Hypersets
A universe composed by rational ground terms ia characterized (both constructively and axiomatically), where the interpreted set constructs land •ith (the latter designating the element insertion operation) coexist with free Herbrand functors. Ordinary syntactic equivalence must be superseded by an equivalence relation ~. between trees labelled over a signature, that suitably reflects the semantics of vith. Membership (definable as "d E t =oo~ ( t vith d) ~ t") meets the non-well-foundedn,ess property characteristic of hyperset theory. An algorithm for solving the NP-eomplete unification problem pertaining to hollow hyperset terms is provided, and shown to be totally correct. An application to the matching of finite state automata is hinted at. Introduction With this paper we wish to contribute to the field of constraint logic programming mainly in two ways. First, by characterizing hyperseb both constructively and axiomatically ( cf. See. 2, 3); then, by specifying a procedure for normalizing constraints of the most basic kind over hypersets. Our procedure will be shown to always terminate and to give the proper results (cf. Sec. 4). A by-product of our constraint normalization procedure is an algorithm for solving a novel NP-complete unifictJtion problem pertaining to hypersets, which has direct applications on its own: it can be used, for instance, to determine whether two finite state automata characterize the same language (cf. See. 5). Hypersets of the kind we will propose are very intimately related to Aczel's nonwell-founded sets (ef. [1]), but they all have finite cardinality and height; moreover they are hybrid, in that their construction involves free Herbrand fun.etors. The finiteness restriction comes from our willingness to regard hypersets as tnstanees of an algorithmic data structure; the proposed hybridization comes from our goal to Q Until. tli Pi .. , Dip. di Inlonn.atica. Cono ltalia -40, 561~Piaa (1). do'fiertdi .uaipi.il ¢ U~ti•. tli Roma "L. Sa,ienza", Dip. di Inl. e Siat. Via Salaria, 113. 00198-Rom&. o.odeoe .. si.dis.uairo .. l.il 6 Uniw. tli Utli"e, Dip. di Matematica e Inlormatica. Via Zanon, 6. 33l~Udine (1). policrited!.i.1111iad.il • Uftiw. tli Parma, Dip. di Matematica. Via M. D'Azepo, 85/ A. -43l~P.vma (1). 1ro••iep~t.aat~ . 1111ipr . il
21945654
Designing Hypermedia Applications with Objects and Patterns
In this paper we present a software engineering approach for building hypermedia applications. Our approach combines the use of an object-oriented method with a system of design patterns for navigational and interface design. We first present the core activities in the Object-Oriented Hypermedia Design Method (OOHDM), namely conceptual design navigation design, abstract interface design and implementation, describing the modeling constructs we use to build high-level, abstract navigational and interface structures. Next we give the rationale for using design patterns in the process of building high quality hypermedia applications, and present some simple patterns solving recurrent design problems. We finally discuss some further issues.
14893766
Improving Web Information Systems with Navigational Patterns
In this paper we show how to improve the architecture of Web information systems (WIS) using design patterns, in particular navigational patterns. We first present a framework to reason about the process of designing and implementing these applications. Then we introduce navigational patterns and show some prototypical patterns. We next show how these patterns have been used in some successful WIS. Finally, we explain how patterns are integrated into the development process of WIS.
11116452
The object-oriented hypermedia design model
H ypermedia applications typically include complex information , and may allow sophisticated navigation behavior. The Object-Oriented Hypermedia Design Method (OOHDM) [4] uses abstraction and composition mechanisms in an object-oriented framework to, on one hand, allow a concise description of complex information items, and on the other hand, allow the specification of complex navigation patterns and interface transformations. In OOHDM, a hypermedia application is built in a four-step process supporting an incremental or prototype process model. Each step focuses on a particular design concern, and an object-oriented model is built. Classification, aggregation and generalization/specialization are used throughout the process to enhance abstraction power and reuse opportunities. Figure 1 summarizes the steps, products , mechanisms and design concerns in OOHDM. Domain Analysis In this step a conceptual model of the application domain is built using well-known object-oriented modeling principles [3], augmented with some primitives such as attribute perspectives (multiple-valued attributes, similar to HDM perspectives [1]). Conceptual classes may be built using aggregation and generalization/special-ization hierarchies. There is no concern for the types Abstract interface objects, responses to external events, interface transformations Running application
47231847
Enhancing a requirements baseline with scenarios
Scenarios are well recognized as an important strategy towards understanding the interface between the environment and the system, as well as a means to elicit and specify software behavior. We have a broader understanding of scenarios: for us, a scenario is an evolving description of situations in the environment. Our proposal is framed by Leite's (1995) work on a client-oriented requirements baseline, which aims at modeling the external requirements of a software system and its evolution. Scenarios start by describing the environmental situation, according to the main actions performed outside the software system. Scenarios also help the clarification of the interrelation between functional and non-functional requirements. We have validated our strategy and related representations based on case studies of a real situation.
38243163
Querying Hypermedia Applications in an Object-Oriented Framework