We discuss the parameterised complexity of answering tree-shaped ontology-mediated queries (OMQs) in OWL 2 QL under various restrictions on their ontologies and conjunctive queries (CQs). In particular, we construct an ontology T such that answering OMQs (T , q) with tree-shaped CQs q is W[1]hard if the number of leaves in q is regarded as the parameter. The number of leaves has previously been...

Indices and data structures for web querying have mostly considered tree shaped data, reflecting the view of XML documents as tree-shaped. However, for RDF (and when querying ID/IDREF constraints in XML) data is indisputably graph-shaped. In this chapter, we first study existing indexing and labeling schemes for RDF and graph data in general with focus on support for efficient adjacency and rea...

this study was designed to investigate the structural characteristics of beech forests in the middle stage of ecological succession. in order to this purpose undisturbed beech stands in kheyroud forest had chosen and three one hectare sampling plot laid out. all of tree species measured with full callipering method and diameter and height of trees were recorded. natural regeneration within one ...

During the next decade, in the wave of microelectronics and digital revolution, we can expect to witness fast growth in the number of communication-based distributed data processing systems. A communication-based distributed data processing system is a decentralized data processing system in which data processing facilities or computer resources are geographically distributed and communicate wi...