On behalf of another UK software company, I implemented a module in a Joomla website for coding content according to the IPSV standard. Take a deep breath.
The IPSV (Integrated Public Sector Vocabulary) is a controlled vocabulary of approximately 7,000 terms, categorised in a hierarchy sometimes up to 7 or 8 levels deep. The IPSV serves as an encoding scheme for use with the Subject element of the e-GMS (e-Government Metadata Standard). By agreeing a consistent set of descriptive terms, search agents are more likely to find successful matches: for example, "Heritage" is a term to be used instead of near-synonyms such as "Conservation" or " Historic environment".
At any level, a term can be selected and attached to that article. The same tagging can be made to whole categories of articles, to avoid needless duplication at the level of articles themselves.
After this preparation, whenever that article is displayed (or, more importantly, found by search engines) the appropriate set of IPSV labels is set into the META statement of the HTML, using "Dublin Core" conventions, viz:
<meta name="eGMS.subject.category" scheme="IPSV" content="Heritage">.