Bøger af Marcelo Arenas

Data exchange is the problem of finding an instance of a target schema, given an instance of a source schema and a specification of the relationship between the source and the target. Such a target instance should correctly represent information from the source instance under the constraints imposed by the target schema, and it should allow one to evaluate queries on the target instance in a way that is semantically consistent with the source data. Data exchange is an old problem that re-emerged as an active research topic recently, due to the increased need for exchange of data in various formats, often in e-business applications. In this lecture, we give an overview of the basic concepts of data exchange in both relational and XML contexts. We give examples of data exchange problems, and we introduce the main tasks that need to addressed. We then discuss relational data exchange, concentrating on issues such as relational schema mappings, materializing target instances (including canonical solutions and cores), query answering, and query rewriting. After that, we discuss metadata management, i.e., handling schema mappings themselves. We pay particular attention to operations on schema mappings, such as composition and inverse. Finally, we describe both data exchange and metadata management in the context of XML. We use mappings based on transforming tree patterns, and we show that they lead to a host of new problems that did not arise in the relational case, but they need to be addressed for XML. These include consistency issues for mappings and schemas, as well as imposing tighter restrictions on mappings and queries to achieve tractable query answering in data exchange. Table of Contents: Overview / Relational Mappings and Data Exchange / Metadata Management / XML Mappings and Data Exchange

This volume contains the proceedings of the 11th International Symposium on Database Programming Languages (DBPL 2007), held in Vienna, Austria, on September 23-24, 2007. DBPL 2007 was one of 15 meetings co-located with VLDB (the International Conference on Very Large Data Bases). DBPLcontinues to presentthe verybest workat the intersectionof database and programming language research. The proceedings include a paper based on the invited talk by Wenfei Fan and the 16 contributed papers that were selected by the programcommittee from 41 submissions. Every submission was reviewed by at least three members of the program committee. In addition, the program committee sought the opinions of additional referees, selected because of their expertise on particular topics. The ?nal selection of papers was made during the last week of July. We would like to thank all of the authors who submitted papers to the c- ference, and the members of the program committee for their excellent work. The program committee did not meet in person, but carried out extensive d- cussions during the electronic PC meeting. We are grateful to Andrei Voronkov for his EasyChair system that made it so easy to manage these discussions. Finally, we would also like to thank Christoph Koch and Gavin Bierman for their assistance and sound counsel, and the organizers of VLDB 2007 for taking care of the local organization of DBPL.

The problem of exchanging data between different databases with different schemas is an area of immense importance. Consequently data exchange has been one of the most active research topics in databases over the past decade. Foundational questions related to data exchange largely revolve around three key problems: how to build target solutions; how to answer queries over target solutions; and how to manipulate schema mappings themselves? The last question is also known under the name 'metadata management', since mappings represent metadata, rather than data in the database. In this book the authors summarize the key developments of a decade of research. Part I introduces the problem of data exchange via examples, both relational and XML; Part II deals with exchanging relational data; Part III focuses on exchanging XML data; and Part IV covers metadata management.