COinS
ContextObjects in Spans, commonly abbreviated COinS, is a method of embedding latent OpenURL ContextObjects in web pages.  This allows client software to retrieve bibliographic metadata and to use an OpenURL resolver to find a mediated link. A principal advantage of using COinS, rather than giving a static OpenURL, is that the client can determine which resolver to use. This allows, for instance, searching for a copy of a book in one's own library.

COinS have been added to various parts of Wikipedia. They are basically just a chunk of bibliographic information stored in a way that machines can read.  This has two applications:

 The information can be converted into a full OpenURL and resolved by a local OpenURL resolver.  For instance, with LibX, OpenURL referrer, or a similar extension or bookmarklet installed in Firefox, a link will appear after many of the books and journal articles in a Wikipedia article's References section.  If the extension is configured correctly, the user can click a link after a book to check if his organization's library has a copy.  If the organization has the appropriate access, clicking the link after a journal article may bring up a copy of the article.
 The information can be stored by bibliographic tools like Zotero. The tool can download the bibliographic information from an article into a personal library for future research and retrieval.
 Zotero also has Wikipedia export, which allows references to be dragged into a Wikipedia edit box, where they will appear formatted as Wikipedia citation templates.

So far, COinS have been added to:

 Wikipedia:Book sources – just contains the ISBN
 Many citation templates and infoboxes – see: :Category:Templates generating COinS
 MediaWiki:Citethispage-content – generated when you click Cite this article; contains information for citing Wikipedia itself in other documents

Template
For use on templates generating COinS:

It adds pages to the above category.

Templates needing COinS
COinS could, and should, be added to these templates:

COinS in citation templates
The COinS keys used in most  templates are listed at Module talk:Citation/CS1/COinS.

For example:

Which renders the following HTML:

Picking out the COinS keys:

Pollution
Incorrect data in fields can pollute the metadata. For example, adding all of the authors into the  field:

See also
 The planned citation microformat

References