As I mentiWordle: Controlled Vocabularyoned last week, my original theme for the month was to go over controlled vocabulary such as the Physics and Astronomy Classification Scheme (PACS) used in Scitation and IEEE Xplore, the Mathematics Subject Classification (MCS) used in MathSciNet, and the Computing Classification System (CCS) used in the ACM Digital Library.  But I decided that there wasn’t enough to say to blog about each one separately.

All of them have similar hierarchical structure like MeSH, but without as many tiers.  PACS has up to 5 subheadings, MCS up to 3, and CCS up to 3.  The headings and subheadings are denoted by some combination of numbers and letters.  Interestingly, the categories of the most recent MCS were determined publicly on a wiki.  The time you’re mostly likely need to use them is if you’re submitting an article to an APS/AIP, AMS, or ACM journal and you need to describe the content of your paper.

But looking at the subjects (controlled vocabulary) for a paper can be very helpful if it turns out the word you’re using is actually not the academic/proper term.  For example, we were helping a student the other day who was interested in fracking (or fracing or fraccing as it used to be spelled before Battlestar Galactica popularized the word frak which was originally spelled frack).  Fracking is a hot topic right now because people seem to think it induces earthquakes.  However, when we looked up fracking in GeoRef, we didn’t get many results.  A quick look at the subjects listed under one of the articles, and it dawned on me that hydraulic fracturing, the proper term for the procedure, is what we should have been looking for.  A quick change in our search and (voila!) many results.