A data feed is a table that contains processed data. The data in the data feed table is calculated using one or more combined data streams. A data stream reads data from a data source, transforms, or calculates data using various operators. A data stream contains at least one data source or transformation operator, or combines multiple operators into a structural or logical unit.
A stream has a name and a type. The type of the steam depends on the calculation result of the last operator listed in that stream. If the last operator is a table operator, producing tabular data, the stream is considered a table stream. If the last operator is a single value operator, producing a single value or a single value list, the stream is considered a single value stream. Single values, such as user inputs or constants, provide data for individual operators.
Depending on the type different colors are used. Tabular operators and streams have teal elements. Single value operators and streams have yellow elements.
Operator and stream connections
Streams and operators can be connected to exchange data. There are two types of connections, connections between streams and connections between streams and operators. Connections between the in and out connectors of two streams are visualized with solid lines. In the example below, there is a data flow between Stream1 and Stream 2, and Stream 1 and Stream 3, each connected with a solid gray edge.
A stream can also be connected to an operator in another stream. This kind of connection is shown as dotted line. In the example below, the single value stream Stream 3 is connected to the Filter rows operator of the Price above average and the Price below average stream.
Example
The following data feed contains six connected streams. Stream 1 has one operator that reads an XML data source. Stream 2 and stream 3 have multiple operators and transform the data. These are data streams of different types. The Column to value operator converts stream 3 into a single value stream. Stream 4 and stream 5 filter the data and add more columns. They are renamed. Stream 6 combines the two individual streams and returns the data to the Output operator.