Position Paper on Binary Interchange of XML W3C Timed Text Working Group Glenn Adams, Chair The Timed Text (TT) Working Group Charter [1] documents the mission of the WG as: "The mission of the Timed Text Working Group (TTWG) is to develop an XML based format used for the representation of streamable text synchronized with some other timed media, like audio and video. A typical application is real time captioning of movies on the Web (e.g. integrated in SMIL)." In addition, the working group has recently published a use cases and requirements public working draft for Timed Text Authoring Format 1.0 [2] in which the following requirement (R110) is stated: "The TT AF shall be capable of being transformed into an idealized streamable representation format." Due to the need to interoperate with binary encoded streaming audio and video formats (e.g., MPEG, Apple QuickTime, Microsoft Windows Media, and others), and due to the nature of these formats being both (1) highly compressed for maximum utilization of limited bandwidth and (2) of a streaming, possibly unbounded form where playback may commence at arbitrary points in the stream, it is presently part of the working group's activity to consider possible binary representations of XML such that the following delivery properties obtain: (1) minimum bandwidth utilization (translating to maximum compression) while still supporting other properties; (2) ability to stream as a sequence of distinct data access units, where presentation access units may or may not be co-terminus with data access units and may be presented in a different order than the order of delivery of data access units; (3) ability to commence playback at arbitrary points in stream within some reasonable constrained interval, e.g., +/- one data access unit; (4) ability to transmit and receive XML infoset items in partial subsets of an instance document's entire infoset; (5) ability to dynamically update a previously transmitted XML infoset item without retransmitting unaffected items; The TT WG encourages the workshop to actively consider the design and specification of mechanisms that meet the above requirements. I am prepared to represent the WG in order to further these aims. [1] http://www.w3.org/AudioVideo/TT/ttcharter20020901.html [2] http://www.w3.org/TR/2003/WD-tt-af-1-0-req-20030515/