In constraint-based program testing, symbolic execution is a technique which allows to generate test data exercising a given execution path, selected within the program to be tested. Applied to a set of paths covering a sufficient part of the code under test, this technique permits to generate automatically adequate test sets for units of code. As databases are ubiquitous in software, generalizing such a technique for efficient testing of programs manipulating databases is an interesting approach to enhance the reliability of software. In this work, we propose a relational symbolic execution algorithmto be used for testing of simple Java methods, reading and writing with transactional SQL in a relational database, subject to integrity constraints. This algorithm considers the Java method under test as a sequence of operations over a set of constrained relational variables, modeling both the database tables and the method variables. By integrating this relational model of the method and database with the classical symbolic execution process, the algorithm can generate a set of Alloy constraints for any finite path to test in the control-flow graph of the method. Solutions of these constraints are data which constitute a test case, including valid content for the database, which exercises the selected path in the method. A tool implementing the proposed algorithm is demonstrated over a number of examples.

This paper presents an experience report on the migration of a COBOL system of over 2 million lines of code. The main goal of this project was to migrate a legacy CODA-SYL database towards a relational platform, while preserving the functionalities of the legacy application programs.

The visualization of ontologies and metadata is a challenging issue with several applications not only in the Semantic Web but also in Software Engineering, Database Design and Artificial Intelligence. This paper aims at identifying and analyzing the more principal aspects of this problem, surveying some of the work that has been done so far, and at proposing novel ideas that are worth further research and investigation. In particular, it describes the main factors that determine whether an ontology diagram layout is satisfying or not and focuses on the visualization requirements of large-sized ontology diagrams.

System evolution most often implies the integration of legacy components, such as databases, with newly developed ones, leading to mixed architectures that suffer from severe heterogeneity problems. For instance, incorporating a new program in a legacy database application can create an integrity mismatch, since the database model and the program data view can be quite different (e.g. standard file model versus OO model). In addition, neither the legacy DBMS (too weak to address integrity issues correctly) nor the new program (that relies on data server responsibility) correctly cope with data integrity management. The component that can reconciliate these mismatched subsystems is the R/W wrapper , which allows any client program to read, but also to update the legacy data, while controlling the integrity constraints that are ignored by the legacy DBMS.This article describes a generic, technology-independent, R/W wrapper architecture, a methodology for specifying them in a disciplined way, and a CASE tool for generating most of the corresponding code.The key concept is that of implicit construct , which is a structure or a constraint that has not been declared in the database, but which is controlled by the legacy application code. The implicit constructs are elicited through reverse engineering techniques, and then translated into validation code in the wrapper. For instance, a wrapper can be generated for a collection of COBOL files in order to allow external programs to access them through a relational, object-oriented or XML interface, while offering referential integrity control. The methodology is based on a transformational approach that provides a formal way to build the wrapper schema and to specify inter-schema mappings.

Due to the current technological and economical context, there is an increasing need for cooperating information systems based on federated databases. Though the technical issues of these architectures have been studied for long, the way to build them has not triggered as much effort. This paper describes a general architecture, a methodology and a CASE environment intended to address the problem of providing users and programmers with an abstract interface to independent heterogeneous and distributed databases. The architecture comprise a hierarchy of mediators and a repository that dynamically transform actual data into a virtual homogeneous database and allow client applications to query it. The InterDB approach provides a complete methodology to define this architecture, including schema recovery through reverse engineering, database integration and mapping building. The methodology is supported by the DB-MAIN CASE tool that helps developers generate the mediators and their repository.

Accessing and managing data from several existing independent databases pose complex problems that can be classified into platform, DMS, location and semantic levels. This paper describes a general architecture, a methodology and a CASE environment intended to address the problem of providing users and programmers with an abstract interface to independent heterogeneous and distributed databases. The architecture comprises a hierarchy of mediators that dynamically transform actual data into a virtual homogeneous database. Each layer provides a certain kind of independence. The InterDB approach provides a complete methodology to define this architecture, including schema recovery through reverse engineering, database integration and mapping building. The methodology is supported by the DB-MAIN CASE tool that helps to generate the mediators and their repository.