Timeline charts on this site display two sets of data over time: numbers of articles published and total usage of a term.
For instance, our automated tagging system produces a timeline chart for 'rdf' that shows 6 articles mentioning 'rdf' were published in October 2008, with total of 21 references to 'rdf' across those articles. For that specified date, the green trend line showing number of articles is therefore set at 6 and the blue trend line monitoring total usage of term is set at 21.
You can hide or show trend lines by selecting labels near top of a timeline chart:
As timeline charts show peaks and troughs over time surveyed, these patterns can be interpreted as general trends in usage across all sources monitored.