Safe use of Meta Tags

It is common to find several ways of representing very similar
concepts in HTML Meta Tags. Yet, metadata authors may wish to
assert that various tags ought to be considered equivalent for
search purposes.

Toward this goal, some of us are trying out a mechanism where
an additional attribute is provided within the Meta element.
The attribute is a "Z" number (corresponding to registered
concepts in the Z39.50 Bib-1 Attribute Set, Use Attributes).
We are putting the Z attribute as the last part of a Meta
element, in the hope that it will be safely ignored by
processors that don't understand what it is. For example,

<title>My Very Own Web Page</title>
<meta NAME="GILS.Originator" CONTENT="U.S. Geological Survey" z="1005">
<link REL="schema.GILS"      HREF="elements.html#table_1">
<meta NAME="AUTHOR"          CONTENT="Eliot Christian" z="1005">
<meta NAME="dc.creator"      CONTENT="Eliot Christian" z="1002">
<link REL="schema.dc"        HREF="http://purl.oclc.org/metadata/dc/">

Is this safe?

Eliot Christian, US Geological Survey, 802 National Center, Reston VA 20192
echristi@usgs.gov  Office 703-648-7245  FAX 703-648-7112  Home 703-476-6134