THE XML REVOLUTION - TECHNOLOGIES FOR THE FUTURE WEB

Document Structure Description 2.0

- a successor to DSD 1.0, a schema language developed in cooperation by BRICS and AT&T Labs Research.

DSD is designed to:

contain few and simple language constructs (based on familiar concepts, such as boolean logic and regular expressions)
be easy to understand, also by non-XML-experts
have more expressive power than other schema languages for most practical purposes

The central ideas in DSD 2.0:

a schema consists of a list of rules
for every element in the instance document, all rules are processed
rules can conditionally depend on the name, attributes, and context of the current element
rules contain declare and require sections
declare sections specify which content (sub-elements and character data) and attributes that are allowed for the current element
require sections specify extra restrictions on content and attributes
attribute values and element contents are described by regular expressions
rule conditions and extra restrictions are described by boolean logic

Main benefits, compared to XML Schema:

the complete language specification is only 15 pages (excluding examples)
no notion of type, rules are directly tied to element names (and no subtyping, substitution groups, or local definitions)
rules can be hierarchical by depending on attribute values and element context
DSD is 100% self-describing (so there is a complete "DSD for DSDs")
lots of non-essential features are removed or reduced to more basic and general constructs

DSD 1.0 was announced in November 1999. The spec for DSD 2.0 is now available!