Introduction
You may wish to start at the About MDDL page.

The Market Data Definition Language (MDDL) has been developed by the Financial Information Services Division (FISD) of the Software and Information Industry Association (SIIA). MDDL is an extensible Markup Language (XML) derived specification, which facilitates the interchange of information about financial instruments used throughout the world’s markets. MDDL helps in mapping all market data into a common language and structure to ease the interchange and processing of multiple complex data sets.

MDDL was launched on 17 January 2001 at the offices of Merrill Lynch, in the presence of some 50 participants from about 35 different FISD member companies. The first release of MDDL was made on 02 November 2001 at the World Financial Information Conference in London. MDDL continued to progress at a dizzying pace through August 2003. With completion of its primary objectives in early 2007, MDDL is now ready for implementation and refinement.

MDDL facilitates the interaction of information between exchanges and other sources, vendors and redistributors, and consumers of market data. “Market data” includes information and statistics about an exchange, the economy in general and other related economic and business factors. MDDL also includes commodity, cash, and foreign exchange components that fall outside the typical realm of simple pricing for securities.

The common market data terminology embraced by MDDL permits the providers to clearly state the nature and origin of market data elements, thus removing ambiguity. The straightforward format of MDDL provides a convenient vehicle for exchanging this data amongst XML aware systems. A system of definitions has been developed that promotes clear understanding and standard interfaces for the securities data flow.