London
MDDL Meeting Report, May 18, 2001
Market
Data Definition Language (MDDL)
Twenty-five
people turned out for an MDDL working meeting hosted by Reuters.
Progress has been made on both the MDDL vocabulary and technical
architecture. The deadline for the delivery of the initial DTD/Schema
for global equities, mutual funds and indices is the FISD working
meeting on June 22.
The
two primary data
dictionary documents (domains and descriptors)
have been updated and posted on the web. FISD members are in the
process of reviewing the documents (particularly the asset class
domain for equities and the indicators domain for indices) for
completeness and accuracy. The Vocabulary Committee is also required
to create a data field map (identifying which descriptors must
be associated with which domain class) and a data relationship
map (identifying which descriptors can also be attributes of other
descriptors).
The
deadline for submitting the revised data dictionary and data maps
(for equities and indices) to the technical committee is June
15.
The
technical committee has taken another step forward in producing
an element-centric
approach to MDDL. This example is best viewed as
a tree, e.g. using Extensibility's "XML Instance".
A
major design rule here is that "<XXX><value>yyy</value></XXX>"
can be represented by the shorthand "<XXX>yyy</XXX>"
so long as "<value>" is the only child of "<XXX>".
This is the mechanism by which elements with text content can
be extended without resorting to mixed content. Properties are
inherited. For example, if an element does not contain a specific
"currency" element, then it inherits the currency of
the nearest ancestor with a "currency" element. The
existence of a "current" child overrides any inherited
currency. The same is true for other properties.
There
is more than one way to write the same information, so different
variations are used in different sections of the document. The
structure of this document is not representative of an actual
document, because some odd structures have been used to demonstrate
how inheritance and overriding of properties works. This is a
first draft for industry reaction. More input is needed from the
vocabulary committee on the details of the information being represented.
The
deadline for development of the draft DTD/Schema is June 22.