More XMLMap: XML about Content (2/3) - exploring XML | WebReference

More XMLMap: XML about Content (2/3) - exploring XML

More XMLMap: XML about Content

DAV Searching and Locating

DAV Searching and Locating is a protocol that enables server-executed queries to locate resources based upon their property values and text content as expressed by the DAV data model. WebDAV and HTTP enable client-side searching by defining a simple set of mechanisms (the PROPFIND and GET methods) to locate those resources meeting client-defined criteria. These mechanisms can be inefficient, inadequate for some simple content based queries, and do not take advantage of the advanced querying and caching capabilities of modern storage systems.

The DASL Protocol will enable a HTTP/1.1 compliant scheme for server-side searching to address these limitations. DASL defines the syntax and semantics of a query and its search results, its scope, and how to discover the search capability of a resource.

Begun with great energy and optimism, work was never completed, and the IETF closed the working group due to lack of progress. However, there is still significant interest in having a protocol for searching WebDAV repositories, and there are several implementations of the existing DASL specification. In early 2002 there has been renewed interest in completing the DASL specification as an individual submission to the IETF.


With new content now popping up everywhere, keeping up-to-date with continuously changing Web sites became more and more of a challenge. New sites were created from frequent updates, such as bloggers, and combining content from different sources, like portals.

RSS was devised as a news syndication format. Syndication is the controlled distribution of information to a set of individuals known as subscribers. There exist as many explanations for the acronym RSS (RDF Site Summary, Rich Site Summary, Real Simple Syndication) as there are versions (0.90, 0.91, 0.92, 1.0, 2.0). The RSS file for this column lists the latest articles, along with a brief description. The file's location is registered with aggregators such as My Netscape, where users can pick their favourite Web channels and thereby receive a live table of contents.

Internet Content Exchange (ICE) is an attempt at automating the syndication process. Today commercial publishers have subscribers and syndicate information in print. Manufacturing companies provide manuals (for maintenance or operation) to individuals that have subscribed by virtue of purchasing products from the company. ICE is designed to facilitate electronic syndication of either of these kinds of information on the Web.

Largely driven by software companies like Vignette, the standard never evolved much from the initial implementations of those products. Either the business is too unusual to be captured by standard software, or not commercial enough to warrant much beyond the scope of RSS.

Content Description

The Semantic Web, or more precisely the lack thereof, is one of the design issues that Web-inventor Tim Berners-Lee identified 1998 as the biggest impediment to further Web growth. Search engines return more and more meaningless results because the Web is not sufficiently self-describing to filter out irrelevant data in any given context.

Meta-data in XML started out with the invention of Resource Description Framework (RDF), an attempt to standardize the way that statements, and relationships between statements and their authors, should be expressed. Being a dorado for graph theory specialists, RDF became the basis for many XML vocabularies in the Artifical Intelligence department, some of which are mentioned below.


Produced by Michael Claßen

Created: Feb 17, 2003
Revised: Feb 17, 2003