rdfxml.py - An RDF/XML Parser in Python

rdfxml.py is a standalone Python module in under 10KB that parses RDF/XML using SAX. It was written to be used as a simple drop-in module for larger projects—for when you just want the smallest and simplest possible module to get the job done. Since it's standalone, it only requires modules that are in the Python standard library; it doesn't force you do download any RDF specific APIs etc. It's been released under both GPL 2 and the W3C's software license.

The module is available as rdfxml.py.txt. Don't forget to rename it to rdfxml.py. The file should have 228 lines and 9433 bytes. Its MD5 is ec83de4e97d4f7e8f05b1eb9dc14a0c1.

Ancillary Documentation

Documentation in the module itself is sparse, but there's not much to know. The parser was written to conform to the 23 January 2003 RDF/XML Syntax Specification Working Draft; with the exception that bagID is no longer supported since the RDF Core WG decided to remove it from the syntax.

It can be used as a command line tool: it takes a URI as the only argument, and produces a list of NTriples. For example:-

Otherwise, the only functions of concern to users are:-

parseRDF(s, base=None, sink=None)

Takes in a string s, and parses it as RDF/XML, calling the "triple" method on the sink with the subject predicate and object as the three arguments for each time a triple is found; try the Sinks section for more information. base gives the optional base URI of the input.

parseURI(uri, sink=None)

A wrapper that opens a URI with urllib first before passing the dereferenced content to the parseRDF function.

Sinks

Sinks must be classes with a triple(self, s, p, o) method. s, p, and o are Python strings corresponding to the subject, predicate, and object productions of the of the N-Triples format's EBNF. It is hoped that this is a usable API-independent way of returning the terms of the triples. Here's an example function that will return a list of (s, p, o) tuples from a string containing RDF/XML:-

import rdfxml

class Sink(object): 
   def __init__(self): self.result = []
   def triple(self, s, p, o): self.result.append((s, p, o))

def rdfToPython(s, base=None): 
   sink = Sink()
   return rdfxml.parseRDF(s, base=None, sink=sink).result

Note that terms may be str or unicode instances.

License

The file rdfxml.py.txt is released under the GNU GPL version 2 or later. There is also another version released under the W3C's software license. The only difference between the two files is the __doc__ string. The W3C software license is fully compatible with GPL.

Rationale and Uses

This code was not written as a competitor to Eikeon's comprehensive RDF parser in his rdflib. I'm sure that his code has undergone a lot more testing than this. This code was written simply because sometimes you don't want to download an entire API when you just want a quick hack. This is a good tool for when you just want triples quickly.

For example, Ken MacLeod has used rdfxml.py in his foaf-check FOAF application. Dan Brickley appears to want a version in Ruby for some project... (Having two users before it's even been released is rather enjoyable.)

But Seriously... Why?

I've been working on an RDF API for a while now. I needed an RDF/XML parser for it, and so here it is. I've been building the API very carefully, with the goal of making it practical. That is, I've only worked on it when I've actually needed it for a project. In that way, I think that it's become quite useful. It's still undergoing major revision, though, so no public releases yet. You can mail me if you want more information or a sneak preview.

To Whom Should I Address Comments/Feedback?

The author, Sean B. Palmer, preferably at sean@mysterylights.com with a CC to www-archive or www-rdf-interest if it's relevant; or sometimes you can find me at #sbp on freenode.