The sections below show how page model and page view are often combined.
Simple pages with no back-end code can be implemented with a single XPL pipeline, XSLT template or static page. A view XPL pipeline must have a data output. The XML generated by the view then goes to the epilogue.
If a page is not sent back to the user agent, there is no need for a view. This is typically the case when a redirect needs to be issued, a binary file is produced, or when a page simply implements an XML service.
This is a variant of the view only scenario, where an XML submission is used. In this case, the view receives the XML submission as the instance input.
This is a variant of the model only scenario, where an XML submission is used.
This is the classic case. An XPL pipeline implements the page model and an XSLT template implements the page view where data produced by the model is consumed by the view.
This is the equivalent of the previous model where an XML submission is used. In this case an instance input is made available to the model and the view.
This is a variant of the previous case where the model declares an instance output. This allows the model to modify the submitted XML instance. This is typically useful when the view displays some values from the XML submission document but these values are not exactly the same as those entered by the user. For example, a page with a text field where the user types an airport code. If the user enters a known city such as San Francisco, the application may automatically add the corresponding airport code (SFO in this case).
