1. Introduction

The Service Registry (SR) is part of the MCP core services, and is used for service discovery and documentation. It fulfills the role of a design-time registry which stores human- and machine-readable documentation about the design and use of services, and a runtime registry containing the current information on where to reach a running service. Both these major parts come with extensive search functionality.

This ensures the ability for service consumers to find the service they want to consume, as well as application developers to retrieve the documentation needed for learning how to interact with a service.

1.1. Basic concepts

To describe services, the SR features a logical concept that separates individual implementations from their design, and furthermore from the implemented service specification. Thus, the three main parts of a service description are as follows:

  • Specification: A technology-agnostic description of a service on a logical level, e.g. "A Weather Service"

  • Technical Design: A description of the technology-bound, actual realization of a service on a technical level.

  • Instance: Information about the actual URI and other relevant data about a specific running service instance.

1.2. Service Specification

A service specification provides operational information about a service without going into detail regarding the technology used. It is a logical description of the data and operations made available by that service, as well as their operational relevance. This information is available in both human readable DOC format, as well as machine-parseable XML, and contains the following:

  • Operational context

  • Interface descriptions

  • Data structures

  • Dynamic behavior

  • Specification author

1.3. Technical Design

The design goes into detail regarding the offered functions in a technology-specific manner, but does not contain information about a specific service instance. It contains:

  • Reference to the corresponding specification

  • Description of the used technology

  • Detailed data structure description (If different from the specification)

  • Design author

1.4. Instance

The service instance is described in human readable form via an Implementation Manual, and in machine readable XML form via the Instance Description.

The Implementation Manual contains detailed information regarding the technologies used in the implementation, deployment instructions, and other instance-specific information. Different instances of the same specification may be run by different operators.

The Instance Description contains the service coverage area, various descriptive fields (keywords, etc.), geographic area, UN/LOCODE, as well as the URI under which to access this service instance.

2. Authentication

The Service Registry is designed to be used in conjunction with the Maritime Identity Registry, which handles authorization. In general, the usage of the Service Registry can be summarized via the following steps:

  1. Authenticate with Identity Registry via certificate/username and password/other means

  2. Receive access token

  3. Send requests to Service Registry, including the access token

  4. Receive and handle the response to the request.

The authentication with the Identity Registry is out of scope for this documentation, as more information on this topic can be found in the corresponding ID Registry documentation. The Bearer Token received from the ID Registry is a Java Web Token in Base64-encoded form, which has to be passed to the Service Registry with every request. The token has a limited time of validity, after which it has to be re-requested. The ServiceRegistry will respond with a HTTP 503 Error if the token is out of date, the authentication token is invalid, or no token was provided. To include the authentication token, it should be included in the HTTP header via the “Authorization” header field as follows:

GET /api/example HTTP/1.1
Host: sr.exampledomain.com
Authorization: Bearer SlAV32hkKG…

The Service Registry API is stateless, there is no http session being used for authentication. The organization ID is encoded within the token and is set by the Identity Registry based on your authentication credentials. Services registered under your organization ID can only be modified by users or clients with the same organization ID.

Both ServiceAdministrationInterface and ServiceLookupInterface work in the same fashion, with the exception of the administrative functions requiring the organization ID of the client to match the organization ID of the resource to be modified.

Tokens may time out, so if the token is rejected, a new token should be requested from the Registry.

3. Basic Usage

3.1. Registering a Service

To register a service, the following steps should be followed:

  • Authenticate with the Identity Registry

  • Register a Service Specification in the SR

  • Register a Service Design in the SR which refers to the Specification

  • Register a Service Instance

If any of the higher level requirements are already met, for example a new instance for an existing Design is to be registered, then the existing items don’t have to be duplicated but can be referenced.

Each of the service fragments (Specification, Design and Instance) consist of a human-readable (in DOC format) and a machine readable part (in XML). The Schema for the XML can be downloaded from the Service Registry.

3.2. Querying the Service Registry

To query the SR for a desired service, the flow is as follows:

  • Authenticate with the Identity Registry

  • Get OAuth2 token

  • Access SR API to query Specifications, Designs and Instance information

3.3. API Access

The SR is accessed by means of a REST API via HTTP protocol. It uses Swagger to describe the API, and an online API overview plus sample generation page can be found at https://sr.maritimecloud.net/swagger-ui/index.html

4. Geographic Functionality

4.1. Service Coverage Geometry

Each service instance may be registered with an associated coverage area. This area is encoded in the service instance XML description, and should be sent in Well Known Text (WKT) format.

The service coverage area may consist of one or more geographic shapes or points. It should be noted that while a service may be defined using just one or more latitude/longitude point coordinates, it is advisable to always use an area shape like a polygon. Otherwise, queries using a point coordinate may not be able to intersect with and find the service instance.

Service coverage geometries follow the right-hand rule, meaning that points of a polygon that encloses an area have to be defined in counterclockwise order. Holes in a covered area (exclusion zones) have to be expressed as a polygon with its points defined in clockwise order.

Services registered with no coverage geometry are treated as being available world-wide, unless an UN/LOCODE has been set.


Alternatively to the WKT geometry definition, service instances may also be registered with a UN/LOCODE. This is an alphanumerical designation that is mapped to a lat/lon coordinate internally. This coordinate is then also considered in geographic searches where the search geometry forms an area, like a polygon. The primary use for UN/LOCODE is a direct match for that designator, so the geographic match is implemented as a secondary means to find location-based service instances.

UN/LOCODE and custom geo-coverage are mutually exclusive. A service instance with an UN/LOCODE cannot also use a custom coverage geometry.

4.3. Geographic Queries

The SR provides several API functions for querying services based on geographic location:

  • searchUnlocode returns service instances that match the given UN/LOCODE

  • searchLocation returns instances whose coverage area intersects with a given lat/lon coordinate.

  • searchGeometryWKT finds all instances whose coverage area intersects with the given search geometry.

  • searchGeometryGeoJSON Same as the WKT search, but accepts the search geometry in GeoJSON format.

Note that the same rules as for the definition of coverage areas (right-hand rule) apply: inclusive shapes have to be in counter-clockwise order, exclusion shapes in clockwise order.

5. Query Filter Format

Most API functions for retrieving service information support an optional field called "query", which can be used to narrow down results based on a set of filter attributes. For example, while a geo-query may return both REST and SOAP services, it is possible to apply a filter so only REST services are returned.

5.1. Available Filter Attributes

  • instanceId

  • specificationId

  • designId

  • name

  • comment

  • status

  • organizationId

  • keywords

  • version

  • mmsi

  • imo

  • serviceType

  • unlocode

  • endpointUri

  • endpointType

5.2. Query

The query parameter is a string with the following layout:

field1:value1 AND field2:value2 AND field3:value3

For example:

serviceType:VIS AND organizationId:SMA