EDelivery
The exchange of a single document between a DE and a DO always requires two eDelivery exchanges: the first one initiated by DE and targeted for DO, and the second one is initiated by DO and targeted for the DE. Technically speaking both transmissions are “requests” even though their semantics are “request” and “response”.
The foundation of the document exchange is the so called “4-corner model”, which differentiates between the business sender of a document (Corner 1 aka C1), the technical sender of a document (Corner 2 aka C2), the technical receiver of a document (Corner 3 aka C3) and the business receiver of a document (Corner 4 aka C4). Depending on the order of a message exchange, the assignment of the corner varies. In DE4A the “DE4A Connector” (sometimes just “Connector”) can play the role of both DR and DT and therefore acts as C2 or C3, depending on whether a message is sent or received.
The figure above depicts the structural message exchange initiated by DE (C1), sent by DR (C2), received by DT (C3) and forwarded to DO (C4). The message exchange between C1 and C2 as well as the message exchange between C3 and C4 are not specified by eDelivery, even though AS4 may be used for this, but they must be defined by the DE4A Connector.
If DO sends a message back to DE, the order of the messages change as well as the corner assignment, as shown in the following figure where the DO becomes C1, forwarding the response to DT which is now C2. The AS4 transmission targets DR as C3 who in turn forwards the payload to DE which is the C4 in this scenario.
This duality of the message exchange means, that each of the named nodes (DE, DR, DT and DO) requires both sending and receiving capabilities.
For the sake of clarity, the rest of the document only shows images with messages flowing from DE to DO because it seems easier to understand, even though the image would be perfectly valid for the return direction from DO to DE (except when stated differently).
The eDelivery message exchange in DE4A uses the so called “Dynamic Discovery” which is an extension of the basic eDelivery in the sense that it adds the usage of SML and SMP. Both components as well as the lookup process are described below.
Identification of components
Each C1 and C4 of a message exchange is called a “Participant” and is uniquely identified by a “Participant Identifier”. The nodes C2 and C3 are not participants and have no respective identifier, they are only accessed by URLs.
Different types of documents exchanged via eDelivery are classified via “Document Type Identifiers”. The orchestrations in which document types are exchanged are classified via “Process Identifiers”.
There is a separate policy document on the usage of identifiers within its network. This document, called “DE4A Policy for the use of identifiers”, contains the details about the following identifier types:
- Participant Identification
- Type Identification
- Process Identification
- Transport Profile Identification
Each Participant ID, Document Type ID and Process ID consists of two separate parts – one “scheme” part and one “value” part. A scheme defines the layout and constraints of the value. This allows to add new types of identifiers in different scenarios, without interfering with existing used identifiers.