Features that intersect with geo:touches (or other topological relationships) will have an intersection geometry that may or may not be part of the composite geometry of the features - eg. two polygons sharings a LineSegment, two solids sharing a face denoted by a linear ring.

the requirements are:

1. topological statements can be made without defining geometries (supported currently)
2. intersections are features that may have calculated geometries and metadata about how that was done,
3. intersection geometries may reference internal components (such as points) of the feature geometries by id.
4. intersection features will have constraints about the allowable geometries - e.g. a geo:Face would require a gml:LinearRing (?)
5. intersection features should be consistent with ISO19017 topology complexes, but may be a subset required for "simple features" including its existing "solid geometry" capabilities.

It is expected to be out of scope for GeoSPARQL to support calculation of these intersections or validation that internal ids are self-consistent, but if the information is expressed an implementation can perform additional integrity checking as desired.