What is usefulness of W3C's "Semantic Data Extractor" in semantically correct XHTML CSS Development?

Question

What is the usefulness of W3C's Semantic Data Extractor?

http://www.w3.org/2003/12/semantic-extractor.html

This tool, geared by an XSLT stylesheet, tries to extract some information from a HTML semantic rich document. It only uses information available through a good usage of the semantics defined in HTML.

The aim is to show that providing a semantically rich HTML gives much more value to your code: using a semantically rich HTML code allows a better use of CSS, makes your HTML intelligible to a wider range of user agents (especially search engines bots).

As an aside, it can give clues to user agents developers on some hooks that could be interesting to add in their product.

After checking validation for CSS and HTML. Should i go for Semantic Data Extractor tool.

What it does. and how it can improved our coding.? Is anyone using it?

And i check some site randomly with but with most of sites it gives error

Using org.apache.xerces.parsers.SAXParser
Exception net.sf.saxon.trans.XPathException: org.xml.sax.SAXParseException: The element type "input" must be terminated by the matching end-tag "`</input>`". 
org.xml.sax.SAXParseException: The element type "input" must be terminated by the matching end-tag "`</input>`".

Is it possible to get validate every site with this tool?

Answer 1

After checking validation for CSS and HTML. Should i go for Semantic Data Extractor tool.

Probably not

What it does.

Exactly what you quoted from its homepage.

and how it can improved our coding.?

Other then hitting you over the head when you have problems counting heading levels; not a lot.

And i check some site randomly with but with most of sites it gives error

It depends on well formed and sane input.