This extension defines a simple mechanism for plugins to map URIs to and from integers, usually for performance reasons (e.g. processing events typed by URIs in real time). Typically, plugins map URIs to integers for things they "understand" at instantiation time, and store those values for use in the audio thread without doing any string comparison. This allows for the extensibility of RDF but with the performance of integers. This extension is intended as an improved and simpler replacement for the uri-map extension, since the map context parameter has been found problematic.
An lv2:Feature which provides URI mapping and unmapping capability. To support this feature, the host must pass an LV2_Feature to LV2_Descriptor::instantiate with URI http://lv2plug.in/ns/ext/urid#URIMap and data pointed to an instance of LV2_URID_Feature.