Domain Registrars need website classification ?
I heard that domain registrars need to know which category a website registered with them belongs to. And if they have such process automated it may help their business.
Since I am working on website classification I would appreciate if somebody could comment it.
Here, let me Google that for you...
Interestingly enough, from the above SERP we find a discussion on it here,
webvit (that wouldn't be one in the same person as the OP, would it?)
Also in that SERP is a paid link to ZVELO, whose tagline reads, "We categorize the web".
Along the lines of subject and theme, your local library will have a Subject Index. In it you can find all manner of classification for how you see your site themed. You know more about your site than anyone, so start by listing (and sub-listing) your subjects in as much detail as possible. Cover all the ground and begin funnelling the lists into smaller fields until you're down to one or only a few main subjects. Now you've classified your own site.
Data classification can help IT staff of your ISP to determine what resource load to expect from your site (and help you decide on the correct hosting plan). Subject classification can certainly help SE's place you in their index in a manner that matches one's expectations.