DJ's Weblog

Here are two or three, er, thoughtbites, that I’ve come across over the past few days and that have stayed with me. I just thought I’d share them here as it’s the weekend and often a good time to think about things.

Open thinking about deep-linking

Tim Bray’s strawman defence of the principle that ‘deep linking’ on the web isn’t illegal. It’s a wonderfully calm and simple aspirin for the anger and frustration that builds up inside when one reads about silly legal action about ‘deep-linking’.

RDF, define thyself

In Sean B. Palmer’s document The Semantic Web: An Introduction (highly recommended!), RDF Schema is introduced, using (amongst other things) this snippet of RDF (read “rdf:type” as “is a”):

rdfs:Resource rdf:type rdfs:Class .
rdfs:Class rdf:type rdfs:Class .
rdf:Property rdf:type rdfs:Class .
rdf:type rdf:type rdf:Property .

I don’t know about you, but I had to go and have a sit down to consider the implications after reading that.

Using namespaces in code

Last week on #rss-dev, Ken MacLeod pointed to a post by Dan Connolly regarding namespaces. Ken said:

A very key point (I think) drawn out in this article is that namespaces are used only to derive a (URI+localname) pair — namespaces should never be considered seperate from the element name they specify. … A namespace and localname make a single item of data, distinct from any other combination of namespace and localname.

Libraries and applications (tools) should not try to store a namespace as one “object” and try to link all of the names as “children” of those objects. So, if you’re working in a language that’s string-happy, like Tcl or Perl, the first thing you should do is take the namespace and element name and put them together and use them like that from then on, “{URI}LocalName” works well in Perl, for example.

Sounds obvious when you grok it, but (for me at least) it was a refreshing way to look at the whole issue of namespaces and how they’re represented in XML and used in deserialised data structures.