latest update: 4 July 2013
NOTE - The above diagram may change
ISO 15926 starts with a data model, as defined in ISO 15926-2. In this ISO standard this data model is written in EXPRESS, the modelling language of the ISO 10303 ("STEP") suite of standards. See here. A graphical access can be found here.
For the purpose of ISO 15926 (integration, sharing, exchange, and hand-over of plant lifecycle information) the choice has been made to use the technologies of the W3C Semantic Web.
The OWL version of the data model can be found here.