[TYPO3-dev] Access Database of foregn extension (including cascading delete …)

[Tobias Wagner]

Hello everyone,

I have a problem in the basic design of my new project cannot find any resources concerning this problem in the web.

I have created some sketches about my domain model with the customer and now want to implement the whole design, starting with the database-layer while using extbase and fluid.
Our team split the requirements in parts, so we would like to create 4 separate extensions for the different requirements, which are operation on one and the same database.

Each of this separate extension mostly uses only a certain part of you whole database, but since we have some 1:n oder m:n relation to tables of our other extensions, there is no hard line to draw between our "separate" extensions.
Especially when a deletion of data happens in extension A, there has to be a cascading delete, which could affect extension B and so on.

We are now facing a problem and cannot find any resources on how to implement our requirements of having separate extensions, which are implemented most separatly from different persons, but at the same time which some kind of "Interfaces" in the database layer.

We planned to use the extension builder (new kickstarter of extbase), for creating the initial structure for each extension separately. Then se thought about connecting the extionsions by manually adding relations to ext_tables.sql (we don't know exactly how to do this, but we thought that it could be done that way). 

So are there any example materials on how to define relationships between extensions (concerning their database fields)?
Can we realize cascading deletes through the borders of one of your extensions, to another of your extension?
Can we develop our extensions separately, based on an initial extension builder project?
Can I use the CRUD operations from my extension A to modify data of any extensions B?

I would really appreciate if you could answer the questions to these fundamental questions to help me decide on how to start the project whichout having to realtize later, that our initial design was wrong.

Best regards,
Tobias Wagner