Segment

• Definition: The smallest building block of an IDoc.

• Represents a logical grouping of fields (like a table structure).

• Each segment corresponds to a set of related data — for example:

  • E1KNA1M → Customer general data (Name, Address, etc.)

  • E1KNB1M → Company code–specific customer data.

• Segments can be mandatory or optional, and they can repeat (e.g., multiple items in a sales order).

When to use:
Use a segment when you want to define a structure for holding related data fields inside an IDoc.

Message Type

• Definition: Defines what business process or message is being sent.

• It acts like a label for the IDoc to indicate its purpose.

• Examples:

  • ORDERS → Purchase Order / Sales Order

  • INVOIC → Invoice

  • DEBMAS → Customer Master

• A message type is linked to a basic type (the structure of the IDoc).

When to use:
Use a message type when you want to represent a business scenario for communication between systems (e.g., sending a sales order, invoice, or master data).

Basic Type (IDoc Type)

• Definition: Defines the structure of the IDoc — which segments it contains, their order, and hierarchy.

• Example:

  • Basic type: ORDERS05

  • Segments: E1EDK01 (header data), E1EDP01 (item data), etc.

• Multiple message types can be linked to the same basic type.

When to use:
Use a basic type when you need to specify the technical structure/layout of the IDoc that holds the data.