Design standard for Page Templates and Sub flow calls in ADF 11g

ADF 11g provides effective ways of reducing development time by allowing to create page templates. So, a typical example of a page template is say your organization app has 20 pages and all having same header and footer (or at least same layout). Now to avoid repetition of designing or copy/pasting manually in all 20 pages you can simply create a page template and use it while creating your pages. Page templates are much more powerful than what I said above as it allows you to keep dynamic data as well. But lets understand it this way as the focus of this post is different.

When a Task Flow call is made from a page fragment which is inside a task flow then the Task flow being invoked is referred as Sub-flow. The design diagram usually represent it by a task flow call activity. So, one of the most typical mistake I have seen people doing in ADF world is wrong way of using the page template in the sub-flows.  You must make sure that if the parent flow is using a page Template A (say with two areas header and content area) then you must not use the same template Template A in any of the page fragment of the sub-flow. The simple obvious reason is: in that case the page fragment of subflow having Template A will be embedded in the parent task flow page fragment. Visually, It is like:

So, what is the right way? Well in case of sub flows you should only use the page Template A in the parent task flow's page fragments. For the subflow page fragments there should not be any page template or there should be another page Template B which is only the content part of the template A.

So, in other words you should create a page Template B with only content part of Template A. And then you should create another Template A with only header part and in the content area including template B. So, for parent flow page fragments Template A should be used and for sub flow page fragment's Template B should be used.