The purpose of ISO 15926 is "Integration, sharing, exchange, and hand-over of distributed Plant Lifecycle Information."
This paper gives a possible scenario.
A picture says more that a thoudand words:
Possible scenario for an EPC project
During the life cycle of a facility hundreds of applications contribute data about activities performed for and by that facility. These data are mapped to objects and templates and stored in a Application Fašade for each of such applications. Such a fašade is a commercial triple store with an API that is (for now: will be) standardized in ISO 15026-9. All Part 9 fašades behave in an identical manner.
Once the discipline or group that uses the application feels that their information is good enough to be shared with others, they can perform a "hand-over" from the applicable Application Fašade to the Project Fašade.
Most applications require data that have been created by others. By means of overnight SPARQL queries each application can be fed with those data. The query results have to be mapped to the internal format of that application.
At the time of a custody transfer of a particular process unit to the plant owner/operator, the applicable data can be selected from the Project Fašade and the custody thereof can be handed over as well.
The plant owner/operator could feed operational data and maintenance data into his Facility Fašade in a similar manner. At the time of a revamp information about the unit to be revamped can be made available to the EPC contractor, thus avoiding mismatches caused by changes due to maintenance taking place during the engineering and procurement activities of that EPC contractor.