Multi-query evaluation over compressed XML data in DaaS

This paper addresses the problem of evaluating a heavy load of subscribed queries (or simply multi-queries) over compressed XML data in a distributed service-oriented DaaS (Database as a Service) environment. We propose a holistic approach that evaluates complex queries over a compressed document and forwards the compressed results directly to the data requestor (DR). Firstly, we review the data management issues in DaaS, and then we will address the multi-queries optimization problem. Secondly, we introduce a new rewriting translation technique to decompose and reorganize a complex query into its corresponding Structure of complex XPath (SXP). Following this, multi-query evaluation is performed based on the containment relationships between the queries. The containment relationships are exploited by a global data structure, the Structural-Query-Index Tree (SQIT), which supports prefix sharing among the submitted queries. The experimental results demonstrate that the proposed approach obtains higher query processing efficiency than traditional ones.