A data stream is any collection of data from one data source. The source determines the type of data stream and, therefore, what type of threshold is applicable. Data sources can be either continuous or discrete:
In continuous data (also known as time series data), each data value represents a point in a continuous curve of information.
In discrete data, each possible data value represents a change of state for the data source.
In this chapter, we are not using the terms continuous and discrete in a strict mathematical way. We are using the terms to distinguish data that changes on a relatively continuous basis (no digital computer-based data is truly continuous) from data that has a discrete set of possible values. ...