Revising Z: part II - logical development

This is the second of two related papers. In "Revising Z: Part I - logic and semantics" (this journal) we introduced a simple specification logic ZC comprising a logic and a semantics (in ZF set theory). We then provided an interpretation for (a rational reconstruction of) the specification language Z within ZC. As a result we obtained a sound logic for Z, including the basic schema calculus. In this paper we extend the basic framework with more sophisticated features (including schema operations) and we mount a critique of a number of concepts used in Z. We further demonstrate that the complications and confusions which these concepts introduce can be avoided without compromising expressibility

Branching: the Essence of Constraint Solving

This paper focuses on the branching process for solving any constraint satisfaction problem (CSP). A parametrised schema is proposed that (with suitable instantiations of the parameters) can solve CSP's on both finite and infinite domains. The paper presents a formal specification of the schema and a statement of a number of interesting properties that, subject to certain conditions, are satisfied by any instances of the schema. It is also shown that the operational procedures of many constraint systems including cooperative systems) satisfy these conditions. Moreover, the schema is also used to solve the same CSP in different ways by means of different instantiations of its parameters.Comment: 18 pages, 2 figures, Proceedings ERCIM Workshop on Constraints (Prague, June 2001

Revising Z: part I - logic and semantics

This is the first of two related papers. We introduce a simple specification logic ZC comprising a logic and a semantics (in ZF set theory) within which the logic is sound. We then provide an interpretation for (a rational reconstruction of) the specification language Z within ZC. As a result we obtain a sound logic for Z, including a basic schema calculus

Variadic genericity through linguistic reflection : a performance evaluation

This work is partially supported by the EPSRC through Grant GR/L32699 “Compliant System Architecture” and by ESPRIT through Working Group EP22552 “PASTEL”.The use of variadic genericity within schema definitions increases the variety of databases that may be captured by a single specification. For example, a class of databases of engineering part objects, in which each database instance varies in the types of the parts and the number of part types, should lend itself to a single definition. However, precise specification of such a schema is beyond the capability of polymorphic type systems and schema definition languages. It is possible to capture such generality by introducing a level of interpretation, in which the variation in types and in the number of fields is encoded in a general data structure. Queries that interpret the encoded information can be written against this general data structure. An alternative approach to supporting such variadic genericity is to generate a precise database containing tailored data structures and queries for each different instance of the virtual schema.1 This involves source code generation and dynamic compilation, a process known as linguistic reflection. The motivation is that once generated, the specific queries may execute more efficiently than their generic counter-parts, since the generic code is “compiled away”. This paper compares the two approaches and gives performance measurements for an example using the persistent languages Napier88 and PJama.Postprin

A temporal versioned object-oriented data schema model

AbstractThis paper describes in a formal way a data schema model which introduces temporal and versioning schema features in an object-oriented environment. In our model, the schema is time dependent and the history of the changes which occur on its elements are kept into version hierarchies. A fundamental assumption behind our approach is that a new schema specification should not define a new database, so that previous schema definitions are considered as alternative design specifications, and consequently, existing data can be accessed in a consistent way using any of the defined schemas

Object-oriented views: a novel approach for tool integration in design environments (dissertation)

Object-oriented databases have been proposed to serve as the data management component of integrated design environments. One central database represents a bottleneck, however, requiring all design tools to work on the same information model and preventing the extensibility of the system over time. In this dissertation, I propose a view-based object server that successfully addresses these problems by supporting design views tailored to the needs of individual design tools.A view on an object-oriented schema corresponds to a virtual subschema graph with restructured generalization and property decomposition hierarchies. I present a methodology for supporting multiple view schemata, called MutliView. MultiView is anchored on the following four ideas: (1) the customization of individual classes using object algebra, (2) the integration of these derived classes into one global schema graoh, (3) the extraction of virtual and base classes from the global schema as required by the view, and (4) the generation of a class hierarchy for these selected view classes. MutliView's division of view specification into these well-defined tasks, some of which have been successfully automated, makes it a powerful tool for supporting the specification of views by non-database experts while enforcing view consistency.In this dissertation, I describe solutions for all four tasks underlying MultiView. For the first task, I have formulated class derivatin operators modeled after the well-known relational algebra operators. For the second task, I have developed a classification algorithm that automatically integrates derived classes into one global schema. For the third task, I have designed a view definition language that can be used to declaratively specify the view classes required for a particular view. For the last task, I have developed an algorithm that generates a complete, minimal and consistent view schema. I present proofs of correctness, complexity analysis, and numerous illustrative examples for all algorithms.MultiView is applied to address the tool integration problem in a behavioral synthesis system. For this purpose, I first develop a unified design object model for behavioral synthesis. I then formulate customized design views of this model tailored to the needs of particular design tools. The resulting system allows the design tools to work on their view of the information model, while MultiView assures the consistent integration of the diverse design data into one object model

Inductive-data-type Systems

In a previous work ("Abstract Data Type Systems", TCS 173(2), 1997), the last two authors presented a combined language made of a (strongly normalizing) algebraic rewrite system and a typed lambda-calculus enriched by pattern-matching definitions following a certain format, called the "General Schema", which generalizes the usual recursor definitions for natural numbers and similar "basic inductive types". This combined language was shown to be strongly normalizing. The purpose of this paper is to reformulate and extend the General Schema in order to make it easily extensible, to capture a more general class of inductive types, called "strictly positive", and to ease the strong normalization proof of the resulting system. This result provides a computation model for the combination of an algebraic specification language based on abstract data types and of a strongly typed functional language with strictly positive inductive types.Comment: Theoretical Computer Science (2002

BSML: A Binding Schema Markup Language for Data Interchange in Problem Solving Environments (PSEs)

We describe a binding schema markup language (BSML) for describing data interchange between scientific codes. Such a facility is an important constituent of scientific problem solving environments (PSEs). BSML is designed to integrate with a PSE or application composition system that views model specification and execution as a problem of managing semistructured data. The data interchange problem is addressed by three techniques for processing semistructured data: validation, binding, and conversion. We present BSML and describe its application to a PSE for wireless communications system design

Model Theory and Entailment Rules for RDF Containers, Collections and Reification

An RDF graph is, at its core, just a set of statements consisting of subjects, predicates and objects. Nevertheless, since its inception practitioners have asked for richer data structures such as containers (for open lists, sets and bags), collections (for closed lists) and reification (for quoting and provenance). Though this desire has been addressed in the RDF primer and RDF Schema specification, they are explicitely ignored in its model theory. In this paper we formalize the intuitive semantics (as suggested by the RDF primer, the RDF Schema and RDF semantics specifications) of these compound data structures by two orthogonal extensions of the RDFS model theory (RDFCC for RDF containers and collections, and RDFR for RDF reification). Second, we give a set of entailment rules that is sound and complete for the RDFCC and RDFR model theories. We show that complexity of RDFCC and RDFR entailment remains the same as that of simple RDF entailment