The representation in the system of a piece of external content is made by a database component containing only meta-data, including type and location information. A concept map, being a component and thus having meta data, is in contrast represented by itself.
To allow these content descriptions to be treated as the content of a specific neuron, we use the relation meta-data entry, with a kind that equals content. While waiting for IMS to define the identifier element to be put here, we use an extension, location, to point to the component representing the content.
In addition, by adding relations with a kind that equals context, we allow the specification of concept maps that act as contexts for the neuron. Please note that concept maps may also serve as content, and that there is an important philosophical difference between the two.