In this paper, we propose the problem of implementing an efficient query processing system for incomplete temporal and geospatial information in RDFi as a challenge to the SSTD community. For the case of incomplete temporal information
in relational databases, two such systems have been implemented in the past, but their query languages are rather limited. There is also the paper which studies a closely related problem, temporal relationships in databases, but which has no related implementations. Finally, the knowledge representation language Telos allows the modelling of incomplete temporal knowledge but well-known implementations such as ConceptBase have not implemented this functionality. To the best of our knowledge, no such relational database system or RDF store exists for the geospatial case, although there are some description logic reasoners that come close in terms of functionality. In the rest of the paper, we present the RDFi framework and outline the hard problems that have to be solved if such a query processing system is to become a reality.
Charalampos Nikolaou, Manolis Koubarakis, "Querying Incomplete Geospatial Information in RDF ", In the 13th International Symposium on Spatial and Temporal Databases (SSTD 2013). Munich, Germany, August 21-23, 2013