Modeling Evaluation Of Continuous Queries on SlidingWindows

One of the distinguishing characteristics of a data stream system is ´a continuous query operating on dynamic data´ as opposed to ´static data processed by instantaneous query´ in DBMS. Due to potentially infinite size of the stream a query is evaluated after forming finite subsets of the data stream. The sliding window model is the most suitable model for processing finite subsets of a data stream where only recent data items qualify. In this paper, we propose a mathematical model to express a continuous query on sliding windows. This model expresses a window as an ordered set. Its sliding mechanism is expressed through a set of transition operations and query evaluation is expressed through a set of output operations