On the Formal Specification and Derivation of Relational Database Applications

The development of database applications is usually carried out informally. The derivation of database programs directly from formal specifications is a well known and unsolved problem. Most of the previous work in the area either tried to solve the problem too generally or was restricted to some trivial aspects, for example deriving the database structure and/or simple operations. This thesis describes an extension to the traditional database design process aimed at formalizing the development of (relational) database applications. Specifically, it gives a complete description of a general method for the specification of relational database applications using Z, as well as a comprehensive description of a set of rules on how to derive database programs from specifications which result from using the method. The method prescribes how to specify all the important aspects of relational database applications, which includes the definition of relations, the specification of constraints, and querying and updating of relations, including error handling. It also addresses more advanced features such as transactions, sorting of results, aggregate functions, etc. However difficult in general, deriving relational database applications directly from Z specifications written according to the method is not arduous. With appropriate tool support, writing formal specifications according to the method and deriving the corresponding relational database programs can be straightforward. Moreover, it should produce code which is standardized and thus easier to understand and maintain. An intrinsic part of the thesis is a prototype which was built to support the method. It provides a syntactic editor for the method and partially implements the mapping for a specific Relational Database Management System (RDBMS), namely the DBPL system

A Review of integrity constraint maintenance and view updating techniques

Two interrelated problems may arise when updating a database. On one hand, when an update is applied to the database, integrity constraints may become violated. In such case, the integrity constraint maintenance approach tries to obtain additional updates to keep integrity constraints satisfied. On the other hand, when updates of derived or view facts are requested, a view updating mechanism must be applied to translate the update request into correct updates of the underlying base facts. This survey reviews the research performed on integrity constraint maintenance and view updating. It is proposed a general framework to classify and to compare methods that tackle integrity constraint maintenance and/or view updating. Then, we analyze some of these methods in more detail to identify their actual contribution and the main limitations they may present.Postprint (published version

State-of-the-art on evolution and reactivity

This report starts by, in Chapter 1, outlining aspects of querying and updating resources on the Web and on the Semantic Web, including the development of query and update languages to be carried out within the Rewerse project. From this outline, it becomes clear that several existing research areas and topics are of interest for this work in Rewerse. In the remainder of this report we further present state of the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs; in Chapter 4 event-condition-action rules, both in the context of active database systems and in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks