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!
Modeling
The Topic Maps Constraint Language (TMCL) is a language for defining schemas and constraints on topic map models. Specifically, TMCL can be used to constrain instances of Topic Maps Data Model. The constraint language provides a constraint model, related validation semantics, and CTM syntax templates for authoring constraints.
Standard
http://isotopicmaps.org/tmcl/
Tools
Onotoa is a visual editor (based on Eclipse RCP) allowing creation of a Topic Maps Ontology per drag and drop.
The TMCL Validator validates a topic map against a schema.
Alternatives
Some software libraries allow annotation of domain specific classes to allow transparent storage and retrieval from a Topic Maps engine.
More Information
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.