Murray was a founding member of the WG and, due to industry churn, holds the record for representing the largest number of different organizations: SoftQuad, Grif, Muzmo, CNGroup, and Veo.
Murray's involvement with XML extends well back before its birth; he was involved in the W3C in its very early days, and was a leader among those lobbying the W3C to bless some sort of SGML-on-the-Web effort. He gets quite a bit of credit for XML's making a prominent splash at the WWW6 conference in April 1997.
The history is even longer than that; Murray was heavily involved in the Davenport group, a clear ancestor of the XML WG in that it included Eve Maler, Dave Hollander, and Jon Bosak as chair.
Finally, although Murray would probably demur, his long and close relationship with Yuri Rubinsky makes me think of him as as representing Yuri's voice in the process.
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