Around the year 2000, a concept called the ‘semantic web‘ was brought together and has continued to evolve since. By 2007, the use of semantic web technology had grown to a point where tim berners-lee wrote an article about the ‘Giant Global Graph‘ that had been forged through the use of it.
SOURCE: http://jmvidal.cse.sc.edu/library/w4012.pdf
Historically, it is noted that a constituent of the origins for these technologies were indeed born out of DARPA Agent Markup Language.
The ‘semantic web’ ecosystem of technologies has an array of different names and technical constituents which have developed overtime.
Critically, semantic web employs the use of RDF in an array of different serialisation formats. Almost any form of data can be converted into RDF.
Once data is stored in an RDF format, it can therefore be employed by systems that provide the means to query data structured in this format. The means through which this is done is most-often by way of a family of query language services denoted moreover as sparql.
Sparql family solutions include (but are not limited to) sparql-mm that provides support for multimedia, Sparql-FED that provides the means to query multiple end-points.
Somewhere around 2009 a rebranding attempt for Semantic Web (“SemWeb”) & RDF; to the term ‘Linked Data‘ was started to be made. Whilst the implication and extensive nature of technology use is not well-known, it is indeed the case that the vast majority of web services contain RDF and are therefore constituent elements of the broader ‘semantic web’.
One of the ways this can be better understood is by reviewing the means through which ontologies are currently used and/or installing relevent plugins that also provide the necessary tools, to make it easier to see the ‘web of (structured) data’.