Default and Required Components
All the templates for the Order Processing pipelines (OPP) include Default and Required components. These components are provided to ensure the integrity of data as it comes into and goes out of a pipeline stage.
In general, Default components appear at the beginning of a stage and site developers will often replace them. Default components are all named as such, DefaultShipping, DefaultPayment, and so on. Default components ensure that critical values for the stage exist. This may involve copying the values of one set of dictionary keys to another set of keys, or initializing some values to zero. If your pipeline does not require special functionality then the default components do not need to be replaced. However, if you need these Default components to function differently you will either need to replace these components with other components included in Commerce Server 2000 or create your own custom components. For more information about creating custom components, see Building Pipeline Components. For a list of components included with Commerce Server 2000, see Pipeline Component Reference.
Required components ensure the integrity of the data as it leaves the pipeline stage. In many cases this involves setting values, and raising errors or warnings. It may also involve checking that values were set in a previous component.
In addition, some Required components (RequiredItemPrice, for example) automatically perform currency and integer conversions at the end of a pipeline stage when the Currency Mode is set to Currency and Integer (compatibility). This means that if a pipeline stage contains only Site Server 3.0 Commerce Edition or only Commerce Server 2000 objects, you do not need to worry about converting the values. For more information about currency handling, see Currency Enhancements.