Relational data may have access limitations, i.e., relations may require certain attributes to be selected when they are accessed; this happens, for instance, while querying web data sources (wrapped in relational form) or legacy databases. It is known that the evaluation of a conjunctive query under access limitations requires a recursive algorithm that is encoded into a Datalog program. In th...

We study the containment, satisfiability, and validity problems for conjunctive queries over trees with respect to a schema. We show that conjunctive query containment and validity are 2EXPTIMEcomplete w.r.t. a schema (DTD or Relax NG). Furthermore, we show that satisfiability for conjunctive queries w.r.t. a schema can be decided in NP. The problem is NP-hard already for queries using only one...

In the 2002 case Simat Corp v. Arizona Health Care Containment System, the Arizona Supreme Court ruled that the Arizona Health Care Containment System must pay for abortions when they are necessary to preserve the health of pregnant women in the system. In the case, the Court ruled that the Arizona Revised Statutes 35-196.02 and the Arizona Health Care Containment System (AHCCCS) policies, whic...

background at altnagelvin, a district general hospital in northern ireland, we have observed that a significant number of hip fracture admissions are later readmitted for treatment of other medical conditions. these readmissions place increasing stress on the already significant burden that orthopedic trauma poses on national health services. objectives the aim of this study was to review a ser...

Query containment is the most fundamental relationship between a pair of database queries: a query Q is said to be contained in a query Q if the answer for Q is always a subset of the answer for Q, independent of the current state of the database. Query containment is an important problem in a wide variety of data management applications, including verification of integrity constraints, reasoni...

This dissertation develops approaches to testing the satisfiability and the containment of XPath queries in the presence of XML Schema definitions in order to speed up XML querying. XML provides a simple yet powerful mechanism for information storage, processing and delivery, and is a widely used standard data format. XPath is a basic language for querying XML data, and is embedded into many W3...

This work discusses the design and demonstration of an in-situ test setup for testing pipeline steels in a high pressure gaseous hydrogen (H2) environment. A miniature hollow pipe-like tensile specimen was designed that acts as gas containment volume during test. Specific areas can be forced to fracture by selective notching, performed on weldment. The H2 used minimised so safely without need s...