Topic Maps is a Web 3.0 enabling technology: Creating rich semantic models. Browsing and searching faceted information. Integration from various data sources. Ultimate flexibilty. Enjoy!
Query languages are used to extract data from a Topic Map. A query may be aligned with the Topic Maps Data Model or specialized or generalized for other use cases.
The Topic Maps Data Model is the heart of the Topic Maps standards and is supported by several file formats, query languages and modeling languages. A topic map in a software system is usually managed using a Topic Maps engine
The Topic Maps Query Language (TMQL) is the most prominent query language for Topic Maps. There exist several versions. The 2008 draft and the 2010 draft are the most prominent.
Other popular languages are TOLOG which is most prominently used with Ontopia
For programmers, many software libraries, called Topic Maps engines are available to use, some of which are part of complete knowledge management solutions.
Students and academics will find the Topic Maps Library useful. It includes many publications, a glossary, information about standards and more.
Many companies offer commercial services and/or consulting around Topic Maps products. The list of sponsors of TMRA is a good place to look for them. The Topic Maps Projects list gives some starting points, too.
The Standards are available through ISO. The latest versions can also be obtained at isotopicmaps.org. The most prominent standard is the Topic Maps Data Model which uses XTM 2 and CTM as serializations.