A Database Interface for File Updates.

Serge Abiteboul, Sophie Cluet, Tova Milo: A Database Interface for File Updates. SIGMOD Conference 1995: 386-397

@inproceedings{DBLP:conf/sigmod/AbiteboulCM95,
  author    = {Serge Abiteboul and
               Sophie Cluet and
               Tova Milo},
  editor    = {Michael J. Carey and
               Donovan A. Schneider},
  title     = {A Database Interface for File Updates},
  booktitle = {Proceedings of the 1995 ACM SIGMOD International Conference on
               Management of Data, San Jose, California, May 22-25, 1995},
  publisher = {ACM Press},
  year      = {1995},
  pages     = {386-397},
  ee        = {http://doi.acm.org/10.1145/223784.223854},
  crossref  = {DBLP:conf/sigmod/95},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}

Abstract

Database systems are concerned with structured data. Unfortunately, data is still often available in an unstructured manner (e.g., in files) even when it does have a strong internal structure (e.g., electronic documents or programs). In a previous paper, we focussed on the use of high-level query languages to access such files and developed optimization techniques to do so. In this paper, we consider how structured data stored in files can be updated using database update languages.

We introduce the notion of structuring schemas as a mean of providing a database view on structured data residing in a file. A structuring schema consists of a grammar together with semantic actions (in a database language). We argue that updates on files can be expressed conveniently using high-level database update languages that work on the database view of the file. The key problem is how to propagate an update specified on the database (here a view) to the file (here the physical storage).

As a first step, we propose a naive way of update propagation: the database view of the file is materialized; the update is performed on the database; the database is ``unparsed'' to produce an updated file. For this, we develop an unparsing technique. The problems that we meet while developing this technique are related to the well-known view update problem. The technique relies on the existence of an inverse mapping from the database to the file. We show that the existence of such an inverse mapping results from the use of restricted structuring schemas.

The naive technique presents two major drawbacks. It is inefficient: it entails intense data construction and unparsing, most of which dealing with data not involved in the update. It may result in information loss: information in the file, that is not recorded in the database, may be lost in the process. The major contribution of this paper is a combination of techniques that allows to minimize both the data construction and the unparsing work.

Copyright © 1995 by the ACM, Inc., used by permission. Permission to make digital or hard copies is granted provided that copies are not made or distributed for profit or direct commercial advantage, and that copies show this notice on the first page or initial screen of a display along with the full citation.

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