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A datastream consists of two types of data adapters: datasources and data filters. Datasources retrieve data from an input source—the COM interface in the case of Siebel reports—and create data rows from the incoming records. Data filters sort, filter, or perform other computations on data rows. While a datastream must have at least one datasource, it is not required to have any data filters, and in the majority of standard reports data filters are not used.
A data filter receives data rows from one or more datasources or other data filters. A data filter processes the data it receives, and then passes it to the next data filter (if there is one) or to the report.
Actuate provides three classes of data filters, one for accepting data from one datasource or data filter, one for merging data from multiple datasources and filters, and one for sorting. In the sscustom library, the classes for these three purposes are ssSingleInputFilter, ssMultipleInputFilter, and ssMemoryDataSorter, respectively.
Sort-merge requirements go beyond the capabilities of the standard sorting and grouping methodology and are handled with a data filter subclassed from ssMemoryDataSorter. This class inherits from the baseMemoryDataSorter class in the sssiebel library and ultimately from AcMemoryDataSorter in the Actuate Foundation classes. A data filter based on ssMemoryDataSorter is also called a sort filter.
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