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6.4 Use Case 4: Dispatcher use cases
Table 5 - Use case 4 - Dispatch
Use Case Identifier: DMS 4 Use Case Name: Dispatcher subscription to client
Use Case Description: Dispatcher subscribes to a client data stream through the DMS. Actors Initiators:
Dispatcher
Actors Receivers:
DMS
Pre-conditions:
The DMS knows the unique identification of the client.
Post-conditions:
Dispatcher receives information of a client or a summary of it.
Basic course of action:
1. Dispatcher sends a subscription request to the DMS, containing the identification of the client it wants to subscribe to, optional filtering options based on classtype
of message, and the Dispatch consumer reference where it wants to receive data copysummary.
2. DMS extracts the client ID from the request and look for the corresponding client. 3. DMS sends to the unique consumer reference endpoint at the DMS
corresponding to the particular client to the dispatcher. 4. DMS memorizes that a data copy or data summary is associated with the
corresponding client.
7 DMS Communication Model
The DMS will in general be required to have a generic functionality, namely that it is able to work not only with OGC services, but also other web services such as FAA or
SESAR SWIM. The DMS specification documented in this report supports communication request-response and publish-subscribe based between an aircraft client
and services on the ground via data link. However, within OWS-9, it is foreseen that the focus will be on facilitating the communication between an aircraft client and OGC-
compliant web services on the ground, namely a Web Feature Service and an Event Service. Specifically, it will be demonstrated that an actively participating client in terms
of performing information request and subscription will be able to obtain information from OGC web services on the ground network through the DMS. However as the DMS
supports request-response based service interactions, in general it should also be able to
19 enable communication with WPS, Registry and WCS. The only constraint is that for
OWS-9 binary content is not supported, thus interaction with FPS or the ePIB WPS is not foreseen. This could be considered as future work in DMS development. The added-
values provided by the DMS in such case include:
Efficient data transmission over wireless link through compression, Reliable communication through the use of reliable messaging,
Additionalmore tailored filtering and validation, in addition to what has been provided by the ground web services.
Continuous performance, quality and provenance control and maintenance
Figure 2 - Service Negotiation
Client DMS
1 : getSessionOptions
2 : getSessionOptionsResponseModule 3 : createSessionendpoint, Module
4 : createSessionResponse
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Figure 3 - Request Reply
Client DMS
OWS Dispatcher
1 : clientRequestendpoint, serviceURL, request 2 : Request
3 : Response
4 : validateresponse
5 : filterresponse
6 : prioritizeresponse
7 : provenanceresponse
8 : clientRequestResponseresponse
9 : createDispatchMessage 10 : CDispatchNotifyNotification
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Figure 4 – Subscription request
Client DMS
1 : clientSu scri eRequestserviceURL, request 2 : replaceConsu erReferencerequest
3 : Su Requestrequest
4 : Su Responseresponse
5 : clientSu scri eRequestResponseresponse
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Figure 5 - Notification
7.1 Detailed protocol
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