A computer-implemented method comprises receiving a plurality of data streams into a data stream management system, wherein each data stream is obtained from a data streaming source and a reliance level is associated with each of the data streaming sources. When a continuous query is registered that specifies a reliance level attribute, the query is executed over the plurality of data streams using only those data streams obtained from a data streaming source associated with a suitable reliance level. For example, the reliance level attribute may establish a minimum reliance level, such that data stream having a lesser reliance level are not used. CQL may be enhanced with such an extra attribute which allows end users to specify the desired reliance level when submitting a query.