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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.



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