Re: XML Query data model, algebra, and stuff

From: Peter F. Patel-Schneider (
Date: 10/12/01

With all apologies to John McCarthy, who should know better, this statement
is at best misleading, and at worst dangerously wrong.

  [[[ ... XML is isomorphic to the subset of Lisp data
     where the first item in a list is required to be atomic. ]]]
  --        1998: Advice for XML, W3 and ICE
  Fri, 07 May 1999 20:56:22 GMT

(I'm couching the differences below in terms of XML Infoset, as that is the
smallest reasonable definition of what is in an XML document.)

Lisp data is not just (standard) lists or ordered trees.  Lisp data can be
circular in many ways.

XML Infosets should (? actually I can't find any prohibition on this in the
infoset document) not be circular in any way.  XML Infosets have
considerable required structure, and many reserved names, and thus are not
just general trees.

Peter F. Patel-Schneider
Bell Labs Research

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