[uf-discuss] multi-word tags

Andy Mabbett andy at pigsonthewing.org.uk
Tue Sep 25 06:12:01 PDT 2007

The rel-tag spec says:

        Spaces can be encoded either as + or %20.

(I think that "can" ought to be an RFC2119 "SHOULD", BTW; other specs
may similarly need to have RFC2119 applied more rigorously).

However, I see sites, in the wild, using dashes (hyphens) and others
which encode spaces as underscores (e.g. del.icio.us; Wikipedia and
other MediaWiki sites). See previously-compiled evidence, at:


Indeed, pages on the microformats wiki use hyphens in URLs which would
seem suitable for use as tag spaces:

        existing rel values

Operator, for example, regards:




as three distinct tags, and does not discard them as duplicates (see
test page at <http://www.westmidlandbirdclub.com/tag-test.htm> ).

What do other parsers and implementations do? Should the spec be
altered, so that the above, and:


are all deemed equal?

Likewise, for that matter:


This might be achieved by saying that spaces in tags SHOULD be encoded
as encoded as either + or %20, but that parsers MUST treat dashes and
underscores as spaces.

Or we could simply say that spaces in tags SHOULD be encoded as encoded
as +, %20, - or _

Andy Mabbett

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