58 Copyright © 2011 Open Geospatial Consortium,
Inc. All Rights Reserved.
and act as WS-N Publishers. Such events are pushed to the Event Services when they become available at the WFSs. The WFS servers also act as a static repository for
retrieval of AIXM features and snapshots as described in section 9.5.1.
Listing 3 – Example digital NOTAM Notification
Listing 3 populates a “Navaid unservicable” DNOTAM using a Tempdelta. It uses the NavaidExtension to link to the Event feature contained in the same XML document.
9.3.3 Data Processing
The actual processing is done by the Event Services. All incoming digital NOTAMs are checked against subscriptions more specifically: the filters they define created by the
clients. If a filter matches for a certain subscription the originally received DNOTAM is pushed to the client without modifying it. This must also be the case if the Event Service
applied enrichment of thin events see section 9.5.1.
9.4 Dynamic Filtering
The OWS-7 Aviation Architecture Engineering Report OGC 10-079, Section 8.4.5 introduced the concept of a dynamic filter for DNOTAM events. During OWS-8 the
wsnt:Notify xmlns:wsnt=http:docs.oasis-open.orgwsnb-2 wsnt:NotificationMessage
wsnt:Message msg:AIXMBasicMessage gml:id=gmlID14726
xmlns:msg=http:www.aixm.aeroschema5.1message xmlns:gml=http:www.opengis.netgml3.2 xmlns:aixm=http:www.aixm.aeroschema5.1
xmlns:dnotam=http:www.aixm.aeroschema5.1event msg:hasMember
dnotam:Event gml:identifier codeSpace=urn:uuid:BCB4F904-9AEA-4F2E-97AE-
2D4A4344BD6Cgml:identifier dnotam:timeSlice
... dnotam:timeSlice
dnotam:Event msg:hasMember
msg:hasMember aixm:Navaid gml:id=gmlID14730
gml:identifier codeSpace=urn:uuid:BCB4F904-9AEA-4F2E-97AE- 2D4A4344BD6Dgml:identifier
aixm:timeSlice aixm:NavaidTimeSlice gml:id=gmlID14731
... aixm:interpretationTEMPDELTAaixm:interpretation
aixm:sequenceNumber1aixm:sequenceNumber aixm:correctionNumber5000aixm:correctionNumber
... aixm:availability
aixm:NavaidOperationalStatus gml:id=gmlID14734 aixm:operationalStatusUNSERVICEABLEaixm:operationalStatus
aixm:NavaidOperationalStatus aixm:availability
aixm:extension dnotam:NavaidExtension gml:id=gmlID14735
dnotam:theEvent xlink:href=urn:uuid:BCB4F904-9AEA-4F2E-97AE- 2D4A4344BD6C
dnotam:NavaidExtension aixm:extension
aixm:NavaidTimeSlice aixm:timeSlice
aixm:Navaid msg:hasMember
msg:AIXMBasicMessage wsnt:Message
wsnt:NotificationMessage wsnt:Notify
Copyright © 2011 Open Geospatial Consortium,
Inc. All Rights Reserved.
59
details for such a concept have been developed and implemented prototypically. Figure 22 illustrates the idea of this concept.
Figure 22 – Dynamic buffer of a flight route
As illustrated in this example a client receives a notification about the activation of an Airspace Time B. Later Time C another Airspace is activated and the formerly
activated Airspace gets inactive again. The clients do not receive notifications for these events as the buffer used as filter geometry is updated dynamically using the position
updates received by the aircraft.
By updating a dynamic subscription using position data a client does not have to manage multiple subscriptions for each route portion and no further requestresponse
communication to update the filter geometry is needed. In addition, another advantage of such a subscription is that no unnecessary information is delivered to the clients. Hence
bandwidth is not wasted and the pilot or dispatcher is not distracted by irrelevant DNOTAMs.
9.4.1 Creation of a Dynamic Spatial Filters
The support for dynamic subscriptions in the Event Service in general can be realized using the Event Pattern Markup Language EML. EML is currently a discussion paper at
OGC OGC 08-132 and several improvements happened to it since its submission. The concept is based on Complex Event Processing CEP to define patterns of Events.
