Thoughts on theTokina AT-X PRO 11-16mm f/2.8 AF DX Lens For Nikon?

So i'm thinking of buying those lens? Are they considered wide angle lens? Would the fit my nikon d3100? Basically i'm looking for wide angle lens used for photographing interior/building/architecture photography?
are they suitable for that?

Of all the third party lenses, Tokina makes the best ones for Nikon and Canon cameras.

It will of course fit your D3100 and if you had looked on the Tokina website, you would have seen that the lens has an internal focusing motor so will work in auto-focus mode

The AT-X line of Tokina lenses are high quality, pro level zooms. In general, they are a step below the pro level lenses built by the camera manufacturers, but they will perform better than the entry level or mid level Nikon lenses. With your crop sensor, this lens is not overly wide, but should be nice for architecture. Two issues may be pin cushioning and parallax, which may require some software to straighten out.

You pick up an extra 1/2 stop with the Tokina, but you might also want to look at the Sigma 10-20 f/3.5 (though this side by side is on a Canon body):
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=718&Camera=474&Sample=0&FLI=0&API=4&LensComp=711&CameraComp=474&SampleComp=0&FLIComp=0&APIComp=3