Free lunch (a free lunch)
The class I wrote above is also very basic, which is to explain the problem, and may also be used for low-visitive sites. If you want to find some more professional things, go online, there are many Open source RDF analyzers, they have a variety of additional features (including cache). Then let us see how to use these analyzers.
The first thing to talk about is the RDF analyzer class developed by Stefan Saasen to the FASE4 website, you can download from http://www.fase4.com/rdf/. This is a very fully equipped RDF analyzer, supports cache and certification by proxy. Here's how to use it:
