The ISO/TC 211 Harmonized UML Model and Resources for Implementation
Dr. Knut Jetlund, Norway
Structured models of concepts for the digital representation of geospatial information and for the services for accessing the information have been an essential part of standards developed by ISO/TC 211 since the committee was established in 1994. The committee resolved to use The Unified Modelling Language (UML) as the conceptual language for standards already in 1998 and have later standardized the use of UML in ISO 19103 and ISO 19109. The first steps towards harmonizing UML models from different ISO/TC 211 standards started in 1999. The Harmonized Model Maintenance Group (HMMG) was established in 2002 to maintain a repository of harmonized UML models of ISO/TC 211 standards and projects. The UML models are maintained in the Harmonized UML Model, which contains all UML models developed and standardized by ISO/TC 211. In total, the Harmonized Model by now contains packages for 52 standards with 112 parts, editions, amendments, and corrigendum.
For most standards developed by ISO/TC 211, a conceptual UML model is the foundation. The standards documents are formal documentation. Normative statements support the models, conformance classes and conformance tests to describe how to use and formally comply with the standards. For the technical implementation, the UML model and the derived resources for implementation are the essential artefacts.
There are two main reasons for maintaining a harmonized UML model for ISO/TC 211 standards: First, the fundamental principle that modelled concepts shall be defined once and reused in other models. The reuse of elements from existing models is an essential part of information modelling, as Noy and McGuinness described in their guide Ontology 101 (Noy and McGuinness, 2001). UML models in the Harmonized Model follow this principle and reuse elements from other ISO/TC 211 standards and models developed by other ISO committees. Besides, a harmonized model with all ISO/TC 211 models lays the necessary foundation for implementing ISO/TC 211 standards in domain-specific UML models that comply with ISO/TC 211 standards.
UML modelling of geospatial information in the Harmonized Model is based on a Model-Driven Architecture (MDA) defined in ISO 19103, with four levels of abstraction, as illustrated in Figure 1, from (Jetlund et al., 2019):
1: The building blocks of information modelling in ISO/TC 211. From (Jetlund et al., 2019)
The upper-most level contains metamodels that define how UML shall be used for describing geographic information, while the second and third levels contain conceptual models that are modelled according to the metamodels and standardized rules for UML modelling. The conceptual models are independent of any implementation technology but may contain semantics needed for implementation.
The second level contains abstract models of basic concepts for representation of, e.g., geometry and coordinate reference systems. These elements are the core building blocks for more application-specific models for applications such as land administration or road networks at the third level. For the most, ISO/TC 211 has focused on the core concepts of geographic information, defined at the abstract conceptual level, while only a few application schemas are standardized by ISO/TC 211. The models of core, abstract concepts need to be stable, while application schemas need more flexibility than what is usually possible for ISO standards. Authorities, agencies, and organizations worldwide have developed a wide range of domain-specific application schemas based on ISO/TC 211 UML models, such as OGC, INSPIRE, IHO, TN-ITS and National Mapping Authorities.
The bottom level contains implementation schemas for specific implementation technologies, such as GML or OWL. By following the MDA approach and applying rules for modelling and conversion, ISO/TC 211 standards, and application schemas based upon these, can be implemented in various implementation technologies. Resources for implementation of ISO/TC 211 standards are derived and made available at www.isotc211.org. XML schemas are maintained by the XML Maintenance Group (XMG), and OWL Ontologies are maintained by the Group of Ontology Management (GOM).
The ISO/TC 211 Harmonized UML Model is maintained with Sparx Enterprise Architect in Sparx ProCloud Services. The model can be accessed in several ways: Through a Web Browser, Through Reusable Assets in Enterprise Architect or through direct access to Sparx ProCloud in Enterprise Architect. Instructions for accessing the model can be found at the HMMG Wiki.
Jetlund, K, Onstein, E, and Huang, L, 2019. Adapted Rules for UML Modelling of Geospatial Information for Model-Driven Implementation as OWL Ontologies. ISPRS International Journal of Geo-Information, 8 (9):365, doi: https://doi.org/10.3390/ijgi8090365 .
Noy, NF, and McGuinness, DL, 2001. Ontology Development 101: A Guide to Creating Your First Ontology. Stanford Knowledge Systems Laboratory, Stanford University, CA, USA. https://protegewiki.stanford.edu/wiki/Ontology101 (10 January 2021).