Introduction

Service design is a step in the service orientation process detailed on the SWIM reference website (https://reference.swim.aero/knowledge/service-orientation-process.html#design). One outcome is a service model (service interface(s), service operation(s), service behaviour).

This page provides guidance on some aspects of service design.

1 Introduction
2 Naming conventions
- 2.1 SWIM-DEFN-140 Service functions
  - 2.1.1 Example of SWIM-SERV-140 using Service Metadata Schema
- 2.2 SWIM-DEFN-240 Service interfaces
  - 2.2.1 SWIM-SERV-240
- 2.3 SWIM-DEFN-270 Service operations
  - 2.3.1 SWIM-SERV-270
3 Categorisation
- 3.1 SWIM-DEFN-100 Service categories
  - 3.1.1 Example of SWIM-SERV-100 using Service Metadata Schema
4 Application Message Exchange Patterns
- 4.1 SWIM-DEFN-210 Application message exchange pattern

Naming conventions

The following section shows how the names appear in a service definition.

In general:

nouns/roles should be as clear as possible.
verbs should be from an agreed list (of examples).

The following documents will help.

SWIM-DEFN-140 Service functions

The functionality expresses the business view of the service. The requirements asks for information about:

the functions expected to be offered by the service in support of its capabilities; and
their expected real world effects.

The service metadata schema introduces the need to name the function.

Natural language is preferred when naming the function. The example below uses two formulations:

Provide ...
... Provision

It is not possible to have a best practice on which is preferred. Both formulations are allowed. The important this to remember is that it is a name and should be as clear and descriptive as possible.

Example of SWIM-SERV-140 using Service Metadata Schema

"generalDescription": {
 "functionality": [{
  "name": "Provide Turbulence Forecast Information",
  "description": "A detailed and product-specific description on the delivered product.",
  "realWorldEffect": "Information is provided continually; the service consumer gets the subscribed data."
 }, {
  "name": "Meteorological Forecast Provision",
  "description": "...",
  "realWorldEffect": "..."
 }]
}

SWIM-DEFN-240 Service interfaces

Advice on naming service interfaces is given in the note to SWIM-SERV-240.

A service may contain multiple interfaces. Some of these may be private or at least interfaces for specific purposes, e.g. Monitoring or Reporting interfaces. Only exposed service interface need to be documented.

SWIM-SERV-240

Note: To improve readability across service descriptions, it is best practice to apply the following conventions for a service interface name

be represented using UpperCamelCase; and
use the <noun> <role> pattern where <noun> is a topic related to the service and <role> describes the roles in a composition/interaction sequence, based on the Message Exchange Pattern that is used.

Example service interface names: FlightPlanCoordinator, FlightPlanSubmitter, ForecastProvider, ForecastConsumer, ClearanceRequester, ClearanceManager, PreDepartureSequencer, FlightInformationPublisher, AlertListener.

It is best to avoid mention of a broker. Indeed, a broker is not necessary when using AMQP.

Examples based on this from the SWIM Registry:

TurbulenceForecastPublisher for https://eur-registry.swim.aero/services/dwd-turbulence-amqp-10
ArrivalSequenceInformationPublisher for https://eur-registry.swim.aero/services/dsna-arrivalsequencedistribution-service-v11
NowCastSatRequest for https://eur-registry.swim.aero/services/dwd-nowcastsat-wfs-10

SWIM-DEFN-270 Service operations

Advice for naming service operations is given in the note to SWIM-SERV-270.

An example of this convention can be seen in the Web Feature Service standard's getFeature, getCapabilities and getFeatureType operations.

The AMQP 1.0 standard uses message queues. A service consumer can subscribe to a specific endpoint (which is user specific) to get a message.

Operations from the service provider point of view, e.g., when a broker is used (see BROKERED_PUBLISH_SUBSCRIBE_WITH_PUSH_MECHANISM) could be publishTurbulenceForecast. The use of the broker should be transparent to the service consumer.

Categorisation

SWIM-DEFN-100 Service categories

The following example shows how to add a service categorisation for a Web Feature Service.

Example of SWIM-SERV-100 using Service Metadata Schema

"serviceCategorisation": {
 "other": [{
  "name": "SERVICE_TYPE",
  "value": "FEATURE_ACCESS_SERVICE",
  "categorisationScheme": {
   "url": "http://reference.swim.aero/information-services/service-categories/CodeServiceType"
  }
 }]
}

Application Message Exchange Patterns

SWIM-DEFN-210 Application message exchange pattern

Guidance on the selection of the application message exchange pattern can be found on the SWIM reference resource pages.