1. A method of distributing market data over a network from a sender to a plurality of receivers, the method comprising: (a) creating at a computer device in real time and on a per message basis a plurality of extensible templates that each that defines a variable length message structure and includes at least one delimiter that is used to identify a repeated group of information and a field outside of a repeating group that specifies the number of occurrences of the group; (b) building at a computer device a plurality of market data messages that each include variable length fields separated by delimiters and an identification of one of the plurality of extensible templates that defines the message structure used in the message; (c) disseminating by the sender a first one of the plurality of extensible templates; and (d) disseminating by the sender a first market data message that identifies and is structured in accordance with the first one of the plurality of extensible templates, wherein the plurality of receivers receive the first market data message over the network, wherein the plurality of extensible templates are changed on-the-fly so that attributes can be added and deleted.
2. The method of claim 1 , wherein at least one delimiter is used to identify a repeated group in a template.