Jean Henrard

Database Design Recovery

The design of a software component, such as a database, is the trace of all the processes, products and reasonings that have led to the production of this artifact. Such a document is the very basis of system maintenance and evolution processes. Unfortunately, it does not exist in most situations. The paper describes how the design of a database or of a collection of files can be recovered through reverse engineering techniques. Recording the reverse engineering activities provides a history of this process. By normalizing and reversing this history, then by conforming it according to a reference design methodology, one can obtain a tentative design of the source database. The paper describes the baselines of the approach, such as a wide spectrum specification model, semantics-preserving transformational techniques, and a design process model. It describes a general procedure to build a possible DB design, then states the requirements for CASE support, and describes DB-MAIN, a prototype CASE tool which includes a history processor. Finally it illustrates the proposals through an example.

Program Understanding in Databases Reverse Engineering

The main argument of the paper is that database understanding (or reverse engineering) requires sophisticated program understanding techniques, and conversely. Database reverse engineering (DBRE) can be carried out following a generic methodology, one of the phases of which consists in eliciting all the implicit and untranslated data structures and constraints. Evidences of these hidden constructs can be found by analysing how the programs use and update the data. Hence the need for program analysis techniques such as searching for cliches, dependency analysis, program slicing and synthetic views. The paper explains how these techniques contribute to DBRE, and describes DB-MAIN, a programmable and extensible CASE environment that supports DBRE through program understanding techniques.

Database reverse engineering: from requirements to CARE tools

This paper analyzes the requirements that CASE tools should meet for effective database reverse engineering (DBRE), and proposes a general architecture for data-centered applications reverse engineering CASE environments. First, the paper describes a generic DBMS-independent DBRE methodology, then it analyzes the main characteristics of DBRE activities in order to collect a set of desirable requirements. Finally, it describes DB-MAIN, an operational CASE tool developed according to these requirements. The main features of this tool that are described in this paper are its unique generic specification model, its repository, its transformation toolkit, its user interface, the text processors, the assistants, the methodological control and its functional extensibility. Finally, the paper describes five real-world projects in which the methodology and the CASE tool were applied.

Strategies for data reengineering

This paper describes and analyzes a series of strategies to migrate data-intensive applications from a legacy data management system to a modern DMS. Considering two ways to migrate the data and three ways to propagate the corresponding perturbation to the program code, the paper identifies six reference strategies that provide different levels of quality and induce different costs. Three of them are discussed in detail and illustrated by the conversion of COBOL files into a SQL database.

Requirements for information system reverse engineering support

This paper proposes a general architecture for information systems (or data-centered applications) reverse engineering CASE environments. Recovering the specifications of such applications requires recovering first those of their data, i.e. database reverse engineering (DBRE). First, the paper describes a generic DMS-independent DBRE methodology, then it analyses the main characteristics of DBRE activities in order to collect a set of minimum or desired requirements. Finally, it describes the main features of an operational CASE tool developed according to these requirements. This study and these developments are being carried out as part of the DB-MAIN and DB-PROCESS projects.

Data Reverse Engineering using System Dependency Graphs

Data reverse engineering (DRE) is a complex and costly process that requires a deep understanding of large data-intensive software systems. This process can be made easier with the use of program understanding methods and tools. In this paper, we focus on the program slicing technique and we show how it can be adapted to support DRE. We present a DML-independent SDG construction approach involving the analysis of database operations as a first stage. We describe a tool based upon this approach and we report on two industrial DRE projects

Data dependency elicitation in database reverse engineering

Database reverse engineering (DBRE) attempts to recover the technical and semantic specifications of the persistent data of information systems. Dependencies between records (data dependency) form a major class that need to be recovered. Since most of these dependencies are not supported by the DBMS, (foreign keys are the main exception, at least in modern relational DBMS), they have not been explicitly declared in the database schema. Careless reverse engineering will inevitably ignore them, leading to poor quality conceptual schema. Several information sources can contribute to the elicitation of these hidden dependencies. The program source code has long been considered to be the richest, but also the most complex, of them. The authors analyze and compare, through their respective quality and cost, different program understanding techniques that can be used to elicit data dependencies.

A tool-supported method to extract data and schema from Web sites

This paper presents a tool-supported method to reengineer Web sites, that is, to extract the page contents as XML documents structured by expressive DTDs or XML Schemas. All the pages that are recognized to express the same application (sub)domain are analyzed in order to derive their common structure. This structure is formalized by an XML document, called META, which is then used to extract an XML document that contains the data of the pages and a XML Schema validating these data. The META document can describe various structures such as alternative layout and data structure for the same concept, structure multiplicity and separation between layout and informational content. XML Schemas extracted from different page types are integrated and conceptualized into a unique schema describing the domain covered by the whole Web site. Finally, this conceptual schema is used to build the database of a renovated Web site. These principles are illustrated through a case study using the tools that create the META document, extract the data and the XML Schema.

Structure elicitation in database reverse engineering

Recovering the semantic description of file and database structures is an important aspect of business application reverse engineering. It includes a particularly delicate activity, namely data structure extraction, i.e. finding the exact data structures and integrity constraints of the database. This process is made more complex than generally expected due to the fact that these structures and constraints often are not explicitly defined, but are translated into implicit constructs, controlled and managed through procedural code or user interface protocol for instance. This paper describes the problem of implicit structure elicitation. It proposes an analysis of this phenomenon, and of the techniques and heuristics that can be used in the elicitation. It develops a set of efficient techniques and a for the elicitation of one of the most common implicit construct, namely the foreign key. The paper also explains how DB-MAIN, a general-purpose database reverse engineering CASE tool, can help analysts elicit implicit constructs, and specifically foreign keys.

Migration of Legacy Information Systems

This chapter addresses the problem of platform migration of large business applications, that is, complex software systems built around a database and comprising thousands of programs. More specifically, it studies the substitution of a modern data management technology for a legacy one. Platform migration raises two major issues. The first one is the conversion of the database to a new data management paradigm. Recent results have shown that automated lossless database migration can be achieved, both at the schema and data levels. The second problem concerns the adaptation of the application programs to the migrated database schema and to the target data management system. This chapter first poses the problem and describes the State of the Art in information system migration. Then, it develops a two-dimensional reference framework that identifies six representative migration strategies. The latter are further analysed in order to identify methodological requirements. In particular, it appears that transformational techniques are particularly suited to drive the whole migration process. We describe the database migration process, which is a variant of database reengineering. Then, the problem of program conversion is studied. Some migration strategies appear to minimise the program understanding effort, and therefore are sound candidates to develop practical methodologies. Finally, the chapter describes a tool that supports such methodologies and discusses some real-size case studies.