First, a definition: while popularly described as information about information it is perhaps more accurately structured information describing content context.
Given that latter definition it is obvious why SEs would - and long have - been utilising metadata. Perhaps the metadata most familiar to webdevs are the 'meta http-equiv=' and 'meta name=' tags found within the head of an HTML document. However, there are many more.
It can be interesting to see which metadata are likely considered and think how that knowledge might be helpful. For instance, for some years - long, long ago - the keywords meta tag was so helpful it was abused until largely dropped from SE consideration, although the original keyword stuffing advice lives on to confuse new comers.
This is not an area that I would get all excited about - an interesting challenge out on the fringes but most of us likely could better spend our time elsewhere. However, you might find it useful to review certain broadly accepted metadata groupings and consider if certain usages might remove ambiguity. And whether it might be best to remove or replace certain application created metadata, i.e. for privacy reasons.
* Dublin Core properties.
* Microformats
* Microsoft Office properties.
* Adobe eXtensible Metadata Platform (XMP).
* Exchangeable image file format (Exif)
* International Press Telecommunications Council (IPTC) NewsCodes
As SEs move into maps and geographical search Digital Geospatial Metadata might be considered a useful read.
~(_°>· (best ASCII avatar in webdev :thumbs: ) suggestion (nose wiggle or ear twitch?) to consider that the metadata utilised by Google's CustomSearch and SiteSearch is likely used to some degree within Google Search is quite logical. If you agree or care read:
* Enabling Rich Snippets in Custom Search
* Structured Custom Search
* More power to metadata
Note: read carefully, there are some interesting inferences worth further research.






