A common search problem in the World Wide Web concerns finding information if it is not known when the sources of information appear and how long sources will be available on the Web, as e.g. sales offers for products or news reports. Continuous queries are a means to monitor the Web over a specific period of time. Main problems concerning the optimization of such queries are to provide high quality and up-to-date results and to control the amount of information returned by a continuous query engine. In this paper we present a new method to realize such search queries which is based on the extraction of the distribution of ranking values and a new strategy to select relevant data objects in a stream of documents. The new method provides results of significantly higher quality if ranking distributions may be modeled by Gaussian distributions. This is usually the case if a larger number of information sources on the Web and higher quality candidates are considered.