This section describes one - important - technique for modularisation: embedding of pages into other pages.

This technique is useful for "rough granular" integration aspects: it is used to arrange pages with a dedicated task (e.g. the maintenance of an order) into other screens (e.g. an overview of all orders). Each page - both the "outer" page and the "inner" page - keep their "page behavior", i.e. they are talking independently to the server.

The hour glass icon indicates that a page is talking to its server adapter. If an "outer" page refreshes its "inner" page, the "outer" page first talks to the server, and afterwards the "inner" page. Therefore, there is more than one roundtrip between the client and the server.

As a consequence, it does not make sense (and it is not intended at all by Application Designer) to build up fine granular integration scenarios in which a group of fields is defined as an embeddable unit being used in several screens. This is the job of controls to easily build up your own one. Controls which you build render a group of controls (e.g. an area for entering an address) and can be re-used in different pages. Controls always talk to the server within the same roundtrip. They are available as design time controls - if you change the behavior of one control definition, all pages using this control have to be regenerated.

It is comparable with C programming. You have libraries that you put directly into your compilation process. If the libraries change, you have to recompile. This is the level of controls. On the other hand, you have units of rougher granularity: e.g. DLLs. These can be changed without letting your program know. This is the level of page integration.