Alexander Borgida

Implementation of a compiler for a semantic data model: Experiences with taxis

The features of a compiler for the Taxis design language are described and discussed. Taxis offers an entity-based framework for designing interactive information systems and supports generalisation, classification and aggregation as abstraction mechanisms. Its features include multiple inheritance of attributes, isA hierarchies of transactions, metaclasses, typed attributes, a procedural exception-handling mechanism and an iteration construct based on the abstraction mechanisms supported Developing a compiler for the language involved dealing with the problems of efficiently representing and accessing a large collection of entities, performing (static) type checking and representing isA hierarchies of transactions.

TORUS: A step towards bridging the gap between data bases and the casual user

Abstract This paper describes TORUS, a natural language understanding system that serves as a front end to a data base management system in order to facilitate communication with casual users. The system employs a semantic network to store knowledge about a data base of student files. This knowledge is used to find the meaning of each input statement, to decide what action to take with respect to the data base, and to select information that must be output in response to the input statement. A prototype version of TORUS has been implemented.

The TaxisDL Software Description Language

The purpose of the TaxisDL language is to express the conceptual design of an information system. The focus of the design process includes the data classes of the proposed system, the functions and transactions manipulating them, and the larger conceptual groupings of these actions into long-term activities, which we call scripts. The design of the language is based on ideas from semantic data models and formal specification languages.

Towards a Compositional Semantic Account of Data Quality Attributes

We address the fundamental question: what does it mean for data in a database to be of high quality? We motivate our discussion with examples, where traditional views on data quality are found to be unsatisfactory. Our work is founded on the premise that data values are primarily linguistic signs that convey meaning from their producer to their user through senses and referents. In this setting, data quality issues arise when discrepancies occur during this communication. We sketch a theory of senses for individual values in a relational table based on its semantics expressed using some ontology. We use this to offer a compositional approach, where data quality is expressed in terms of a variety of primitive relationships among values and their senses. We evaluate our approach by accounting for quality attributes in other frameworks proposed in the literature. This exercise allows us to (i) reveal and differentiate multiple, sometimes conflicting, definitions of a quality attribute, (ii) accommodate competing views on how these attributes are related, and (iii) point to possible new definitions.

Specification and Refinement of Databases and Transactions

The development process of data-intensive information systems passes through several stages from requirements modeling through conceptual design down to implementation. In DAIDA we used the language TDL for design specification and DBPL, a procedural database programming language with persistent values and transactions, for implementation. In focusing on the transformation from TDL to DBPL we discuss the relationship between the specification and various refinement steps that lead to efficient database programs. As a framework for transformations we use Abrial’ s Abstract Machine formalism. TDL-designs can be mapped into Abstract Machines, which are then the subject of refinement. The complete reification of TDL designs is illustrated by an example.

Some formal results about stratificational grammars and their relevance to linguistics

We present a formal model for stratificational linguistics, and examine its properties such as generative power, complexity of recognition and descriptional complexity. By relating stratificational grammars to control grammars and Szilard languages, we obtain a table of language families generated by stratificational grammars under several restrictions of linguistic interest. In the process, we show that context-sensitive control grammars with leftmost derivations are no more powerful than context-free ones, and, using this, resolve two open problems of Ginsburg and Spanier. Throughout the paper, formal results are interpreted in terms of their significance for linguistic theory and practice.

Measuring and Comparing Effectiveness of Data Quality Techniques

Poor quality data may be detected and corrected by performing various quality assurance activities that rely on techniques with different efficacy and cost. In this paper, we propose a quantitative approach for measuring and comparing the effectiveness of these data quality (DQ) techniques. Our definitions of effectiveness are inspired by measures proposed in Information Retrieval. We show how the effectiveness of a DQ technique can be mathematically estimated in general cases, using formal techniques that are based on probabilistic assumptions. We then show how the resulting effectiveness formulas can be used to evaluate, compare and make choices involving DQ techniques.

Properties of Information Modeling Techniques for Information Systems Engineering

ion mechanisms. These determine the proposed organization of an information base using a particular conceptual model. This is a fundamental concern for conceptual models because organizations that are natural and intuitive lead to more usable information bases which can be searched effectively and can grow without users losing track of their contents. Tools. If an information base is to scale up and remain useful for a long time, it needs tools which perform information base operations efficiently, also ones that support analysis of its contents, to give users confidence that they are correct and consistent. The reader may have noticed that the proposed characterization ignores the methodologies supported by a particular conceptual model. This omission is deliberate. All methodologies that have been proposed, including ones used in practice, are specific to particular uses one intends for an information base. For instance, using an information base for requirements engineering, e.g., [Coad89], calls for a very different methodology than, say, one used for data modeling [Batini92], or knowledge engineering in AI [Hayes-Roth83]. Properties of Information Modeling Techniques 31

Data and activities: Exploiting hierarchies of classes

We wish to briefly discuss recent work in conceptual modelling from a slightly different point of view in order to highlight the parallels between data and transactions, and then mention some benefits of this view. A time-honoured way of describing a system (portion of the world) is by positing a domain of objects and then inter-relating them through function and predicate symbols. The resulting description is a set of axioms in a FOPC. If the world is dynamic, one usually augments the description with the notion of time or state, in which case axioms can be divided naturally into “general laws” (heretofore constraints ) holding in all states, and state-specific “facts”. Given states, one then also has the ability to describe state transitions ( events ) as predicates on pairs of states or, as shown below, as objects in their own right.