Why should I always use Extension Includes rather than Append structure?

[Surendra_Karma]

Hello SAP Community,

Recently, I came across a recommendation for Extension Includes. It states:

"SAP often uses extension control to enforce the use of extension includes.

Extension includes are specific structure types that are included in one or several database table definitions. If customers or partners want to add fields to the table, they have to create an append structure for this extension include rather than a direct append for the database table.

The main benefits are as follows:

• The software provider can use the same extension include in several database table definitions and structure types. This ensures that additional fields are added to several tables in a consistent way.
• The software provider can decide to release only the extension include and not the database table definition itself."

Now, my assumptions are as follows:

1. If I need to extend all database objects where the same Extension Include has been used, the recommendation is correct.
2. If I need to extend just one database object and it has a specific Extension Include, the recommendation is correct if scalability is not a concern in the future for other DB objects.
3. However, if I need to extend just one database object with an Extension Include that has been used in multiple other database objects, I think the recommendation should be to use an APPEND structure.

Please let me know whether my third assumption is correct or if I have missed something, or if there are some design challenges I might encounter with direct APPEND or indirect APPEND in the extension include.

[Sandra_Rossi]

It's best to include the context when asking a question, i.e. the text is coming from here: https://learning.sap.com/learning-journeys/acquire-core-abap-skills/extending-dictionary-objects_b0c... . The recommendation is for the case that you want to add one field to all database objects of the extension include, but your "third assumption" is about a different case. If you want to add one field to only one database object, of course don't add the object to the extension include (whatever it's added directly or via an append structure), because the field would be added to several database objects. Note that it's not a "design challenge", you just don't have the choice. Also, I don't understand why you are presenting your first two assumptions if you don't want us to give our opinion about them.

[Surendra_Karma]

@Sandra_Rossi: Thank you for sharing the link to the text. Additionally, please note that I made my two earlier assumptions to confirm whether my understanding is on the right track. Feel free to enlighten me if there is anything else I should know.