In A Conceptual View of Citation Indexing, which is chapter 1 of Citation Indexing — Its Theory and Application in Science, Technology, and Humanities (1979), Garfield says of the problem of changing terminology and semantics:
Citations, used as indexing statements, provide these lost measures of search simplicity, productivity, and efficiency by avoiding the semantics problems. For example, suppose you want information on the physics of simple fluids. The simple citation “Fisher, M.E., Math. Phys., 5,944, 1964” would lead the searcher directly to a list of papers that have cited this important paper on the subject. Experience has shown that a significant percentage of the citing papers are likely to be relevant. There is no need for the searcher to decide which subject terms an indexer would be most likely to use to describe the relevant papers. The language habits of the searcher would not affect the search results, nor would any changes in scientific terminology that took place since the Fisher paper was published.
In other words, the citation is a precise, unambiguous representation of a subject that requires no interpretation and is immune to changes in terminology. In addition, the citation will retain its precision over time. It also can be used in documents written in different languages. The importance of this semantic stability and precision to the search process is best demonstrated by a series of examples.
Question: What subject does a citation represent?
Question: What “precision” does the citation retain over time?
Exercise: Select any article that interests you with more than twenty (20) non-self citations. Identify ten (10) ideas in the article and examine at least twenty (20) citing articles. Why was your article cited? Was your article cited for an idea you identified? Was your article cited for an idea you did not identify? (Either one is correct. This is not a test of guessing why an article will be cited. It is exploration of a problem space. Your fact finding is important.)
Extra credit: Did you notice any evidence to support or contradict the notion that citation indexing avoids the issue of semantic diversity? If your article has been cited for more than ten (10) years, try one or two citations per year for every year it is cited. Again, your factual observations are important.