General questions on IDOCs and IDOCs for 2 Accounting Interface BAPIs

Question

This post involves several questions pertaining to the topic of IDOC creation. I downloaded a couple of PDFs and tried googling for material on that, but things are far from being clear in my mind.
I tried to put my questions in some order, so we can follow a line of reasoning. Here we go, then:
I have one code where I there are calls to 2 BAPIs:
- BAPI_ACC_ACT_POSTINGS_REVERSE and
- BAPI_ACC_GL_POSTING_REV_POST
I am supposed to prepare/create an IDOC to perform the activities these BAPIs are responsible for, for the sole purpose of providing us much more details on the activities being executed in the system - this is one of the IDOC's features, if I got it right, its highly detailed logging of everything that is going on behind.
Now, the 1st question arises:
From the material I read, I understood that IDOCs are nothing more than data containers, whose sole purpose is to provide a means of communication between two different systems/parties - one of them would usually be SAP. If this is right, than what sort of IDOC would be this one I am supposed to build - if there's not going to be any inter-system communication ? Doesn't it sound strange that pure "data containers" can work as "logging functions" ? Please share some light here.
The 2nd question - after I understand what an IDOC really is - is
then connected to the job I have to do. I found 2 IDOCs which I think have the proper/correspondent basic types for the 2 aforementioned BAPIs. They are, respectively:
- ACC_DOCUMENT_REVERSE01 and
- ACC_GL_POSTING_REVERSE01
Getting back to my understanding of IDOCs, I got that every IDOC is generally made of one control record, data record(s), and status record(s). 3rd question: Where do the segments fit in ? Are the segments definitions of the Data Records ? And why is it that some IDOC types have header segments only and others doesn't have one ? (header segments are not the same as control records, right ?)
Finally, what is the general process flow for creating/preparing an IDOC ? I looked over a couple of forum posts about this but some of them differ one from another in the order of the steps, some don't mention this or that step, so I am still confused.
4th and last question: what comes first ? The definition of a partner, the bonding of a message type with an IDOC basic type, definitions of the inbound/outbound interfaces ?
Any help here would be highly appreciated.
Thanks in advance,
Avraham

Answer 1

Hi Jaya,
Answer 1. Class is a template for creating objects. Object can also be called as instance.
Interfaces allow you to use different classes in a uniform way (polymorphism).
Answer 2. Normal abap is a procedural programming where as by using abap objects we can achieve object oriented programing.
Answer 6. Source code:
In below code i have created a interface and a class which is implementing the interface. I have declared a reference variable of type interface and created a object. Then i have called a method.
REPORT  ZABAPOBJECTS_INTERF.
      INTERFACE I1
INTERFACE I1.
  METHODS METH1.
ENDINTERFACE.                    "I1
      CLASS C1 DEFINITION
CLASS C1 DEFINITION.
  PUBLIC SECTION.
    METHODS: METH2.
    INTERFACES: I1.
ENDCLASS.                    "C1 DEFINITION
      CLASS C1 IMPLEMENTATION
CLASS C1 IMPLEMENTATION.
  METHOD I1~METH1.
    WRITE: / 'This is a method one'.
  ENDMETHOD.                                                "I1~METH1
  METHOD METH2.
    WRITE: / 'This is a method two'.
  ENDMETHOD.                                                "METH2
ENDCLASS.                    "C1 IMPLEMENTATION
START-OF-SELECTION.
  DATA : REF1 TYPE REF TO I1.
  CREATE OBJECT REF1 TYPE C1.
  CALL METHOD REF1->METH1.
Question 7: Yes we need to create a class but most probably we use the existing classes.
Regarding BAPi's go through the below links,
http://www.sapgenie.com/abap/bapi/example.htm
http://www.sapdevelopment.co.uk/bapirfc/bapirfchome.htm
Regards,
Azaz Ali.