The RAP scaffold

Every transactional app in ABAP Cloud is a RAP business object, and a managed BO is assembled from five mandatory artefacts. The persistence is a DDIC table (or a CDS table function over a custom table); on top of it sits an interface CDS root view entity — `define root view entity` — that carries the model and its annotations. That interface view is the stable, technical layer.

The projection CDS view exposes a tailored subset of the interface entity to one service, declared with `provider contract transactional_query`; this is the contract a UI or API actually consumes, so it can hide fields and add consumption annotations without disturbing the interface layer. Behavior is split the same way: a behavior definition for the interface entity (declaring create/update/delete, fields, validations, determinations) and a thin projection behavior definition that re-exposes the operations the service offers via `use create/update/delete`.

Finally a service definition (`define service`) lists which projection entities to expose, and a service binding turns that definition into a concrete protocol endpoint — OData V4 UI being the default for Fiori. The reason for the two-layer split (interface vs projection, BDEF vs projection BDEF) is decoupling: SAP and you can evolve the underlying model while each service keeps a narrow, versionable contract, which is exactly the Clean Core promise applied inside your own code.

ABAP@accesscontrol.authorizationcheck: #check
@endusertext.label: 'Order Header'
define root view entity zi_orderheader
  as select from zorder_hdr
{
  key orderid,
      customerid,
      orderdate,
      total,
      currency,
      locallastchangedat
}

ABAPmanaged implementation in class zbp_i_orderheader unique;
strict ( 2 );

define behavior for zi_orderheader alias orderheader
persistent table zorder_hdr
lock master
authorization master ( instance )
etag master locallastchangedat
{
  create;
  update;
  delete;
  field ( readonly ) orderid;
  field ( mandatory ) customerid, orderdate;
  validation validatecustomer on save { create; field customerid; }
  determination calculatetotal on save { create; update; }
}

Source notes: clean-core-curriculum §4.1