Query Dissemination and Routing

This process will start after the query optimization phase. It means the optimized queries must be propagated throughout the network. So this can be started from the root node of the network with a broadcast of the query. In this case, the query must notice to each sensor in the network based on the query applied method. If the query applies locally then it must be broadcast to its child nodes also in the network routing tree. This is because in Aquisitional query processing technique it is important to identify the path of query where to be disseminated. According to this concern, it will help to reduce the costs of queries incorrect initiating in Acquisitional query processing environments such as in TinyDB application.

When doing query dissemination process in the network that there are two important concerns should be taken into account. Those are, if a query does not affect at an exacting node, and the node that is query applied doesn’t have any child nodes, then there can be removed the whole sub tree from that query. In doing so, it is much more conserve battery power of the sensor nodes reducing the costs of query dissemination, executing and results forwarding across the network. As well as, it will concern about nodes of the network with extending the life time of them. In this case, the process is to determine the node that need not participate in a particular query is a difficult task. But there are two situations have been considered to be taken into account to make this task in better way.

One usual situation is having constant valued attributes with a selection predicate that is nodeid or location. It shows that those nodes do not need participate for the query. Likewise, if a node knows that none of its child nodes will ever satisfy the value of some selection predicates then it does not also need to forward the query to its sub tree. It seems to be an energy efficient way in query dissemination process this is because, before a particular query disseminates it searches the query path that should be queried upon conditions earlier mentioned. In this way, making the routing information of the network in a better way and that will benefit for sensors to extend their lifetime much more.