As we have seen in the previous section, this promises to be a challenging task since a naive extension of our definitions to such constructs is likely to increase reasoning complexity. Also, we want to take into account features of SPARQL 1.1 [17] such as GRAPH, NOT EXISTS and property ...
The verification scheme used in this algorithm consists of naively checking all possible alignments of the pattern against the window. Each possible start position takes O(m)-time and there are m possible start positions for a window of size 2m−1 so it takes O(m2)-time in total. The ...
SPARQL is the standard query language for RDF data. The distinctive feature of SPARQL is the OPTIONAL operator, which allows for partial answers when complete answers are not available due to lack of information. However, optional matching is computationally expensive—query answering is PSPACE-complet...
The problem of two-coloring a graph is feasible, while the problem of three-coloring a graph is thought to not be feasible. Third, we investigate problems that cannot be solved. Even in this realm one can have a notion of one problem being harder than another....