Some operations on database universes

Operations such as integration or modularization of databases can be considered as operations on database universes. This paper describes some operations on database universes. Formally, a database universe is a special kind of table. It turns out that various operations on tables constitute interesting operations on database universes as well.

Operations on (ordered) interval sets

Intervals play an important role in various kinds of database-applications in practice, for example in historical, spatial, and temporal databases. As a consequence, there is a practical need for a clear and proper treatment of various useful operations on intervals and interval sets in a database context. However, the semantics of some important operations on interval sets are not always treated or not treated very clearly in the literature; e.g., often they are defined in an algorithmic rather than a declarative manner. Moreover, implementation proposals are often not as straightforward as they could be. This paper presents a declarative treatment of various operations on interval sets, also introducing some new notions (such as ordered interval sets, their visible points, and their surface). Then the paper formally ?links? such (mathematical) intervals to their database representations. Finally the paper provides straightforward translations from these formal database representations to standard SQL, without the need for SQL extensions.

Some operations on database universes

Operations such as integration or modularization of databases can be considered as operations on database universes. This paper describes some operations on database universes. Formally, a database universe is a special kind of table. It turns out that various operations on tables constitute interesting operations on database universes as well.

A general treatment of dynamic constraints

This paper introduces a general, formal treatment of dynamic constraints, i.e., constraints on the state changes that are allowed in a given state space. Such dynamic constraints can be seen as representations of "real world" constraints in a managerial context. The notions of transition, reversible and irreversible transition, and transition relation will be introduced. The link with Kripke models (for modal logics) is also made explicit. Several (subtle) examples of dynamic constraints will be given. Some important classes of dynamic constraints in a database context will be identified, e.g. various forms of cumulativity, non-decreasing values, constraints on initial and final values, life cycles, changing life cycles, and transition and constant dependencies. Several properties of these dependencies will be treated. For instance, it turns out that functional dependencies can be considered as "degenerated" transition dependencies. Also, the distinction between primary keys and alternate keys is reexamined, from a dynamic point of view.

A framework and a tool to generate e-business options

In early stages, many organizations started to use the internet in more or less ad hoc and experimental ways. After this first stage of learning and experimentation there often arises a need for more systematic approaches to identify, order, and assess e-business options. This paper addresses this need and presents a framework as well as a tool supporting this framework, helping management to generate and order e-business options for their organization. The framework consists of two parts. The first part covers the identification of the dimensions of e-business options. Six dimensions are identified: external stakeholders groups, stakeholder statuses, channel strategies, communication modes, products/service groups, and product/service statuses. Users of this framework can apply these dimensions given the specific characteristics of the organization at hand. Subsequently, these dimensions are combined, generating, in many cases, a multitude of potential e-business options. The second part of the framework supports the process of ordering this large set of generated potential e-business options given certain criteria. This can be accomplished by ordering the dimensions as well as the elements along each distinguished dimension. Some of these elements are company-independent, while others are company-dependent. The framework is illustrated by a case study as a running example. We also offer a design of a tool supporting our framework. The framework focuses on e-business options between an organization and its current or new external stakeholders: possible internal e-business applications are excluded in this paper. The framework can be used as a tool for practitioners, such as consultants or managers, to generate e-business options for a company. They can use it -for example- in workshops to support idea-generation with respect to e-business planning in a creative and structured way. The framework also contributes to theory by providing a method that systematically offers new possibilities for using the internet. After the identification and the ordering of e-business options, the generated and ordered options have to be assessed and selected; this paper however, only focuses on the generating and ordering process.

Federation views as a basis for querying and updating database federations

This paper addresses the problem of how to query and update so-called database federations. A database federation provides for tight coupling of a collection of heterogeneous component databases into a global integrated system. This problem of querying and updating a database federation is tackled by describing a logical architecture and a general semantic framework for precise specification of such database federations, with the aim to provide a basis for implementing a federation by means of relational database views. Our approach to database federations is based on the UML/OCL data model, and aims at the integration of the underlying database schemas of the component legacy systems to a separate, newly defined integrated database schema. One of the central notions in database modelling and in constraint specifications is the notion of a database view, which closely corresponds to the notion of derived class in UML. We will employ OCL (version 2.0) and the notion of derived class as a means to treat (inter-)database constraints and database views in a federated context. Our approach to coupling component databases into a global, integrated system is based on mediation. The first objective of our paper is to demonstrate that our particular mediating system integrates component schemas without loss of constraint information. The second objective is to show that the concept of relational database view provides a sound basis for actual implementation of database federations, both for querying and updating purposes.

Teaching and practicing RE for agility

During the development of an information system, requirements might constantly change. The practice of Information Systems Engineering clearly evolved because of the adoption of agile methods. However, after practice and theory of agile development, teaching agile development should follow. We have to let our students experience agile development and to teach them how to deal with it, not only in theory but also in practice. E.g., in practice it is difficult to keep everything consistent in a constantly changing situation. Also, for students it is (very) strange that something which is judged good in an earlier stage might be judged wrong in a later stage. In this paper, we describe how we simulate agility in our course and how we let the students experience constantly changing requirements, and how we teach them how to handle that. And because of a sudden pandemic (COVID), we were forced to teach all this on-line, with all its educational restrictions (e.g., no personal meetings, limited human interaction/dynamics, etc.).</p