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European Commission Digital

Service Metadata Locator (SML) service

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About the service

The Service Metadata Locator (SML) is the key component that enables dynamic discovery of participants in message exchange networks. As a result, these networks can scale up without being affected by the management of an increasing number of participants. Instead of having participants managed by a central node, address resolution becomes fully distributed and consequently much more scalable.

eDelivery SML Service uses DNS (Domain Name System) lookups to find information concerning a given participant in a message exchange network. This approach does not need a single, central server to run the discovery interface (with its associated single point of failure). Instead, the use of the DNS makes it highly resilient. At runtime, the SML uses decentralised DNS for load balancing of requests, thus supporting a full European-wide upscaling of performance. Since eDelivery interfaces with the global DNS system, the SML can virtually operate 24/7/365. In case of failure, participants would still be able to discover each other based on the information stored on the DNS.

The current eDelivery SML Service implements both the eDelivery SML specifications and the PEPPOL Transport Infrastructure SML specifications. It is based on the sample implementation of the SML software maintained by the European Commission.

Users of the service 

The eDelivery SML Service is intended for the following type of users:

  • Service Providers: may offer services to integrate national backend systems with eDelivery SML Service or to install and operate a eDelivery SML Service.
  • Software Providers: may develop software conformant with the specifications of the eDelivery SML Service to sell it as a commercial product or as an Open Source project.
  • Policy Domain Owners: may use the eDelivery SML Service to help them build their policy network and facilitate the dynamic registration and discovery of participants.

Benefits for the users of the service

The eDelivery SML Service has been designed to generate a list of benefits to the users of the service:

  • Dynamic, global and centralized information management about the participants' SMP location on a Domain Name System (DNS) out of the box;
  • Well established processes and procedures supported by the eDelivery Support office;
  • Scaling up of message exchange networks with hundreds or thousands of participants.



eDelivery SML Service offering description

Last updated: 21 November 2022



eDelivery SML Service level arrangement

Last updated: 08 April 2022

The terms and conditions of the Building Blocks can be consulted in the Master Service Arrangement.
The way European Commission is processing personal data belonging to the users of SML service can be consulted in the eDelivery privacy statement for SML service

Service Level Arrangement Monthly reports