Optimizing regular path expressions using graph schemas

Cost-based Query Optimization for Xpath

“…At the logical level, the XML query optimization is to utilize the XML Schema, and to apply the rules of normalization or simplification to the inner query expressions so as to simplify the expressions that can improve the query performance. Lots of researches focusing on logical optimization have been done [3,4,5,6,7,9,10]. Our work focuses on the cost-based query optimization at the physical level and deals with how to determine the join order in query trees according to the cost estimation.…”

Semantic Query Optimization in an Automata-Algebra Combined XQuery Engine over XML Streams

“…As mentioned in Section 2, the absence of source subelement in a news element would filter out this news while the absence of keyword would not. Furthermore, we apply type inference [3] on the query trees so that nondeterministic navigation steps such as "//" or "*" are resolved as much as possible.…”

“…Schema knowledge is used to rewrite a query into a more efficient one. Most current literature on SQOs in XML focuses on techniques that are either (1) general regardless of persistent or streaming XML sources [1] or (2) specific to persistent XML sources [3]. For example, query tree minimization [1] is a general technique.…”

“…Since the pruned query involves less computation than the original one, it is more efficient to evaluate regardless of the nature of data sources. For another example, the query rewriting using state extents [3] technique requires indices on the data. Applications on persistent XML can usually afford the preprocessing of building indices while this is often not the case for XML stream applications due to the on-the-fly arriving nature of their data.…”

A Fast Algebraic Web Verification Service

“…Our embedding relation closely resembles the notion of simulation (for the formal definition, see [2]), which has been widely used in a number of works about querying, transformation, and verification of semistructured data (cf. [6,1,15,5] It is important to have an efficient implementation of homeomorphic embedding because it is used repeatedly during the verification process as described in the following.…”