How-to-validate

= How to validate your XHTML+RDFa page =
Q: I have enriched my page with RDFa now. How can I make sure it is done properly?

A: Validate it!

Q: [http://validator.w3.org/docs/help.html#why-validate Why] should I want to validate? 

A: You already said it, right? ;)


Ok, so what is needed to validate an XHTML+RDFa page? What follows is a step-by-step instruction - it's so super easy, everybody can do it (even [http://rdfa.info/wiki/User:MichaelHausenblas I] managed to do it :). 

== Prepare ==
Some tiny steps in advance. Note that you '''don't need''' to go through it, however, it helps minimising the error-rate in advance, hence saves you a lot of time (otherwise you maybe have some iterations in the actual validation step).


=== Include the correct DTD at the top of the page ===
Right before the <nowiki><html ...></nowiki> element you'll need:

 &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN" "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd"&gt;
=== Make sure it is 'proper XML' ===
In W3C-tech-talk this is called [http://en.wikipedia.org/wiki/XML#Well-formed_and_valid_XML_documents well-formed], however it just means close your tags properly (e.g. <nowiki><span>XXX</span><span>ZZZ</span></nowiki>, rather than <nowiki><span>XXX<span>ZZZ</nowiki>) and nest them correctly (e.g. <nowiki><div><span>YYY</span></div></nowiki>, rather than <nowiki><div>XXX<span>ZZZ</div></span></nowiki>).


=== Some extra bits from XHTML ===
I usually forget to check if certain attributes are used correctly. For example, each <nowiki><img></nowiki> needs an <nowiki>@alt=</nowiki> and you should use <nowiki>@id=</nowiki> rather than <nowiki>@name=</nowiki>. This can be nasty regarding forms, etc. but it is necessary.


The other thing you should be aware of is to encode the ampersand in URIs, that is use <code><pre>http://example.com/q=a&amp;amp;b</pre></code> rather than <code>http://example.com/q=a&b</code>.

== Validate ==
Now, let's assume you want to validate the page http://sw-app.org/mic.xhtml, that is check if this is a proper XHTML+RDFa page. Note that we can only do the syntactic check, here; this is no gurantee that the resulting RDF is somehow semantically sound.


The good news is that you're nearly there: <span style="color: red;">Navigate to</span> http://validator.w3.org/ and you should see the following:

[[Image:validator-screenshot.png|center|W3C Validator]]

Note that if you don't have the page online, yet you can also upload a file or paste in the code (see the other two tabs in the W3C Validator).


Next, <span style="color: red">hit the Check'' button</span> and you're done!

Have a look at the output. If all plays well you can reward yourself with adding the following to your page:
 &lt;p&gt;
  &lt;a href="http://validator.w3.org/check?uri=referer"&gt;&lt;img src="http://www.w3.org/Icons/valid-xhtml-rdfa" alt="Valid XHTML + RDFa" /&gt;&lt;/a&gt;
 &lt;/p&gt;

Finally, enjoy validating!