In recent years, the use of ontologies (=logical theories) to access instance data has become increasingly popular. The general idea is that an ontology provides a vocabulary or conceptual model for the application domain, which can then be used as an interface for querying instance data and to derive additional facts [2, 6]. In this presentation, I will introduce ontology-based data access for...

This paper describes a repeatability test, comparing conventional X-ray diffraction (XRD) analyses with the technique of quantitative X-ray diffraction (QXRD) as a determinant of mineral abundance. The conjunctive use of both methods allows specific mineral abundances to be matched between scene of crime (SOC) and suspects where soil or substrate mineralogy is similar. In our test, samples from...

A document type deenition (DTD) D deenes the structure of elements permitted in any web document valid with respect to D. From a given DTD D we show how to derive a number of simple structural constraints which are implied by D. Using a relational abstraction of web databases, we consider a class of conjunctive queries which retrieve elements from web documents stored in a database D. For simpl...

Climate change can result in significant impacts on regional and global surface water and groundwater resources. Using groundwater as a complimentary source of water has provided an effective means to satisfy the ever-increasing water demands and deal with surface water shortages problems due to robust capability of groundwater in responding to climate change. Conjunctive use of surface water a...

Searchable encryption allows a remote server to search over encrypted documents without knowing the sensitive data contents. Prior searchable symmetric encryption schemes focus on single keyword search. Conjunctive Keyword Searches (CKS) schemes improve system usability by retrieving the matched documents. In this type of search, the user has to repeatedly perform the search protocol for many t...

Conjunctive query answering plays a prominent role in applications of description logics (DLs) that involve instance data, but its exact complexity was a long-standing open problem. We determine the complexity of conjunctive query answering in expressive DLs between ALC and SHIQ, and thus settle the problem. In a nutshell, we show that conjunctive query answering is 2ExpTime-complete in the pre...

This technical note presents the ubiquitous problem of query containment for conjunctive queries (an NP-complete problem), and an elegant implementation CQCP of Conjunctive Query Containment in Prolog, in just 7 lines of code. We also describe two important applications of conjunctive query containment: semantic query optimization and minimization. The latter can be implemented by another conci...

Hi-Desert Water District (HDWD), the primary water-management agency in the Warren Groundwater Basin, California, plans to construct a waste water treatment plant to reduce future septic-tank effluent from reaching the groundwater system. The treated waste water will be reclaimed by recharging the groundwater basin via recharge ponds as part of a larger conjunctive-use strategy. HDWD wishes to ...