A vocabulary is a list of terms and, often, their definitions. When a vocabulary includes definitions, it’s called a dictionary. When it includes lists of like terms, it’s called a thesaurus. These tools help prevent semantic dispersion by helping people put things in the proper categories and keeping topics pure. For example, a language like XBRL, the business reporting language, uses a restricted vocabulary of terms that come from a taxonomy that lives online. Each term has a very precise definition. On the other hand, if you are trying to figure out what topics people are talking about on TV, blogs, and Twitter feeds, you need to do a lot of work to discern what people mean when they type or say things. Vocabularies can help categorize and define what people mean unambiguously. They can be ordered alphabetically, hierarchically, or in more complicated relative structures.
There are thousands of professional vocabularies at work, from describing works of art to subject headings for books to legal terms and much more. In the semantic web, these reference works become online resources everyone can use to make their content (transcripts, contracts, books, news articles, tweets, etc.) more findable and interoperable. The more our software can make sense of what we are saying, the more it can help us find other content (and people) that might be useful.
Restricted vocabularies help us build the semantic web. If people writing WikiPedia entries would use a restricted vocabulary, the entire database would become much more linked. Related concepts could be found more easily. Restricted vocabularies prevent semantic dispersion, and that is an important part of building the semantic web.
There are many in-house dictionaries that aren’t online. There are plenty of online vocabularies that aren’t standards for their industries. None of these approaches will ultimately scale to meet the needs of the semantic web.
Here are some of the companies and groups helping build this future:
The Getty Foundation’s CDWA catalog for describing works of art project is online and available.