Version numbers in namespaces considered harmful
The various flavours of RSS offer a variety of namespace requirements:
| URL | RSS version |
|---|---|
http://my.netscape.com/rdf/simple/0.9/ |
0.9 |
| (default) | 0.91, 0.92, 0.94 |
http://purl.org/rss/1.0/
|
1.0 |
http://backend.userland.com/rss2 |
2.0 |
In my opinion, it is a grave mistake to include a version number
in a namespace URI. The function of a namespace is to prevent
accidental collisions between names defined by different people
(or organizations) when two XML vocabularies are combined in one
document. The version number of the format can be specified
separately (as indeed all the RSS versions do, as an attribute
of their root element). If the 0.9 spec had only used
http://netscape.com/1999/rss as its namespace
(following the lead of
http://www.w3.org/1999/xhtml) then all
the versions could have used the same namespace.
Why do I care, you ask? Because if you use actual XML tools like XSLT to manipulate RSS feeds, then the fact that there are three or four namespaces in use for essentially the same elements makes the whole thing more complicated. Where I might have had
<xsl:template match="/rss:rss/rss:channel">...
I better be prepared for more complicated expressions like
<xsl:template match="/*/*[lname()=channel]">...
(to allow for any root element, and to ignore the namespace of
the channel element). This clutters the XSLT file
and makes it harder to maintain—and probably also less
efficient. Sigh.
This is not unique to RSS, by the way—I had all sorts
of hassle with early ve4sions of SVG tools which were caught out
by the ever-changing SVG namespace URL. They finally settled on
the quite-sane http://www.w3.org/2000/svg.