If your Web presence doesn't extend beyond (X)HTML web pages, you are only participating in Web usage Dimension 1.0.

If your Web presence goes beyond (X)HTML pages, via the addition of REST or SOAP based Web Services, then you re participating in Web usage dimension 2.0.

If you Web presence includes all of the above, with the addition of structured data interlinked with structured data across other points of presence on the Web, then you are participating in Web usage dimension 3.0 i.e., "Linked Data Web" or "Web of Data" or "Data Web".

BTW - If you've already done all of the above, and you have started building intelligent agents that exploit the aforementioned structured interlinked data substrate, then you are already in Web usage dimension 4.0.