DE4A Directory
The purpose of the DE4A Directory is to collect all Business Cards of all Participants from all SMPs in the network and provide different query interfaces and a management interface. It offers a GUI for searching by humans and as well a REST API for automated querying. Further details, including the API details and Business Cards definition, can be found in the official Peppol Directory specification.
The DE4A Directory is deployed as a single, centralised instance. The reason to have this centralised is the speed of execution and the technical feasibility. If this wouldn’t be centralised, each query would need to be run against all known SMPs and aggregated afterwards. The execution time would be at least as slow as the execution time of the slowest of the queried SMPs.
The following figure depicts the flow of the communication. The left side of the image focuses on the filling of the Directory, whereas the right part focuses on the querying and searching.
The Directory is NOT involved in the core eDelivery message exchange. It is only used to determine the Participant Identifier of the DO based on parameters such as document type and the ATU. Once the Participant Identifier was found the regular eDelivery message exchange can begin.
Technically the DE4A Directory stores all searchable data in a local Apache Lucene Index which offers great indexation and search speed. The access to the Directory is primarily via an HTTP interface invoked solely by the IAL service.
In DE4A the Directory is mainly an “in-between” service between the different SMPs and the IAL service. Its user interface just comes in handy to check if registrations and business cards are correctly indexed, but for production exchanges only its APIs are of relevance.
The current URL, hosted by Aeioros, is https://de4a.simplegob.com/directory/ - it is running an instance of the Open-Source phoss Directory branded for DE4A. Each SMP must use its SMP certificate as a client certificate when communicating with the DE4A Directory.