This presentation will demonstrate techniques for declaring and exploiting the use of controlled vocabularies using JSON schemas for data exchange, in applications such as the OGC API-Features service interface (and any other OpenAPI implementations.) The approach takes a modular approach with tools to support composition to match reused schema elements to reusable JSON-LD contexts, allowing implementations to simplify profiling by adding additional constraints, such as vocabulary usage, to specific sub-elements of an overall application schema. The approach uses open source tools based on the "OGC Building Blocks" model - part of the full-spectrum interoperability resource now known as the OGC Rainbow.AcknowledgementsThe Institute of Research is supported by the Australian Government through the NationalCollaborative Research Infrastructure Strategy, NCRIS.References1. OGC Building Blocks2. OGC Rainbow