Should be not business logic (eg.

Creation of entity in B dependend on entity already exist (have ID) in repository A Deletion of entity in A will be canceled if entity B still have reference to A.

Reference is Link Many.

Data is a wraper for proto Message It is used to store information related to the datastore itself Such as indexing data like: ID (primary key), Main Ref ID (foreign key) An URL (if any) Update date Also some basic indexing such as last update date.

OptGetParam represent Optional Get Paramaater to be passed to repository when doing Get.

Stores your data in the internet and assign ID to resource so it can be located It stores the data using user ID.