The reference to "this namespace" is without any reference in the sentence.
Best guess is the VML namespace, but could also be the SpreadsheetML og DocumentML mentionen in the sentence before

Clarify either by giving the excat name of the namespace in reference.

Page 4343
Line 3 Part 4
Section 6.1

Ed

Proposed Disposition of DIS 29500 Comment DK-0091 (Modified: 2007-12-05) Agreed; the following change will be made to Part 4, §6.1, page 4,343, line 4: This The urn:schemas-microsoft-com:vml namespace provides the base elements and attributes for defining shape primitives. Similar Comments: DE-0136 , GB-0478 , PT-0109 , US-0275