XML Databases - DADML

Date:      Wed, 17 Mar 1999 17:10:18 +0100
From:      "E.L. Willighagen" <egonw@SCI.KUN.NL>
To:        XML-L@listserv.heanet.ie
Subject:   Re: Requirements for a Web-Based XML Yellow Pages

I agree on your requirements. About a year ago I developed DADML which does basically the same. Only this week I added some Perl support (XML::Parser) and posted the attached email.

That email (posted to Perl-XML listgroup) show how I addressed the issue of how to make information accessible through basic web-technologies.

It supports MIME (it was not specifically developed for XML docs), access of the information through http-servers, indexing and more.

Subject:    XML Databases
From:       "E.L. Willighagen" <egonw@sci.kun.nl>
Date:       Tue, 16 Mar 1999 09:51:05 +0100 (MET)

About a week ago someone asked about xml-databases serving up xml-docs. One responsoe was that a simple http-server is such a server. I disagree. Not totally, but to some extend: mostly a database is considered a structured set of data. The Internet is not. Of course, one can add structure making a HTML file with an url list.

However, DADML -a xml-language I wrote- can also add some structure to a WWW based database. In DADML anyone is able to make a Definition of how to Access a Database (DAD), what indexed items are available (optional), and the definition of a superdatabase. This superdatabase just points to dadml databases and is able to see them as one.

A working example can be found in the Dictionary on Organic Chemistry (1). If you point the browser to, for example, acetic acid (azijnzuur in Dutch), it will view you the result of a simple query, ie. something like SELECT * WHERE index = CAS-NUMBER & value=65-19-7.

This file (2) is made by Java-code, and was compiled from a super.xml (3) and two database.xml (4). Such a query-result can also made on-the-fly with a Perl-script using XML::Parser (great stuff, BTW). In this way the link to certain fields in some of the databases can be checked for availability.

Moreover, this combination of Perl, XML, and standard Web-technology greatly shows how good XML a standard is. How easy it it to serve up XML documents.

More information on DADML with documentation, the dictionary example, source codes and more can be found at (5).