Overview
ISO/IEC 19756:2011 - Topic Maps Constraint Language (TMCL) defines a machine-readable vocabulary for expressing constraints on Topic Maps instance data. TMCL is specified as a Topic Maps vocabulary (identified by Published Subject Identifiers, PSIs) rather than a new textual syntax. It enables precise schema definitions for Topic Maps, supports validation of topic maps against those schemas, and provides CTM templates to simplify schema authoring.
Keywords: ISO/IEC 19756:2011, TMCL, Topic Maps, constraint language, validation, CTM templates, Published Subject Identifiers (PSIs)
Key topics and technical requirements
- TMCL as a Topic Maps vocabulary: TMCL constraint constructs are represented using Topic Maps topics, associations, occurrences and roles identified by PSIs - TMCL itself has no independent syntax.
- Validation semantics: The standard defines both constraint validation rules (how individual constraint topics are validated) and global validation rules (rules that apply to any topic map regardless of schema).
- Schema composition: A TMCL schema is a set of constraint topics plus declaration topics (topic types, association types, role types, name types, occurrence types).
- CTM templates: ISO/IEC 19756 provides CTM (Compact Topic Maps) templates to facilitate authoring TMCL schemas using CTM notation.
- Constraint types covered (from the standard’s normative clauses): topic type, name type, occurrence type, association type, role type, overlap declarations, and a broad set of constraint forms such as subject identifier/locator constraints, occurrence datatype, uniqueness, regular-expression matching, scope and reification constraints.
- Interoperability and datatypes: TMCL references TMDM (ISO/IEC 13250-2) model constructs and XML Schema datatypes where applicable; it also defines comparison rules for special cardinality values used in CTM.
Practical applications and users
- Validation tools: Implementers build validators that check Topic Maps against TMCL schemas to ensure conformance and data quality.
- Schema-driven editors: Editors can leverage TMCL schemas to drive UI constraints, input validation, and guided authoring workflows.
- Data integration and object mapping: TMCL enables mapping Topic Maps to object models or other data formats by providing explicit schema constraints.
- Who benefits: Topic Maps tool developers, information architects, knowledge engineers, semantic web practitioners, digital librarians, and organizations using Topic Maps for controlled knowledge representation.
Related standards
- ISO/IEC 13250-2:2006 (Topic Maps Data Model - TMDM)
- ISO/IEC 13250-6 (Topic Maps Compact Syntax - CTM)
- ISO/IEC 18048 (TMQL - Topic Map Query Language)
- XML Schema Part 2: Datatypes (for regex and datatype matching)
TMCL makes Topic Maps schemas explicit, machine-processable, and interoperable - enabling robust validation, tooling, and schema-driven workflows for Topic Maps applications.