A non-relational stream is a continuously generated, ordered collection of data items that are not relational tuples and therefore not readily processed by relational algebraic operators such as selection, projection, join, and aggregation. Each data item may be associated with a time stamp that represents the time when that data item was produced or received by a certain device or system. Many applications require highly efficient, low-latency, real-time processing techniques in order to keep up with high-volume data streams.
Non-relational data streams have been studied in the following forms: graph streams, spatial streams, text streams, and XML streams.
Each data item represents an insert, update, or delete operation on a vertex or an edge in a graph. Queries on these streams are concerned with estimating properties of the graph or finding patterns within that graph. See “Graph Mining on Streams”.
Spatial data streams represent the...