Resource references Other features Interoperability

Copyright © 2010 Open Geospatial Consortium, Inc. 121

12.2.9.8 Geosynchronization

One of the services in the OWS-7 test bed that implemented notification was the Geosynchronization service. The GSS uses ATOM as the preferred event encoding format but the specification does not specifically mandate which format shall be used to encode notification messages sent to subscribers. During the OWS 7 test bed, both ATOM and CAP were used for encoding notification messages sent to subscribers. The choice of which format a subscriber would receive was made using an outputFormat parameter on the subscribe request. The following listing illustrates a notification message, encoded using CAP, generated by a GSS and sent to a subscriber when a new event i.e. entry appears in one of the services event channels i.e. feeds: 122 Copyright © 2010 Open Geospatial Consortium, Inc. Listing 6: CAP encoded notification generated by ESS cap:alert xmlns:cap=urn:oasis:names:tc:emergency:cap:1.1 cap:identifierurn:uuid:885e061e-b6dd-4a4b-ad15-8131e61c512acap:identifier cap:sendergeosynccubewerx.comcap:sender cap:sent2010-06-03T20:56:41-05:00cap:sent cap:statusActualcap:status cap:msgTypeAlertcap:msgType cap:sourcehttp:www.cubewerx.comows7cubeservcubeserv.cgi?service=GSSamp;request=Ge tCapabilitiescap:source cap:scopePubliccap:scope cap:info cap:categoryOthercap:category cap:eventNEW REPLICATIONFEED ENTRYcap:event cap:responseTypeNonecap:responseType cap:urgencyFuturecap:urgency cap:severityUnknowncap:severity cap:certaintyObservedcap:certainty cap:eventCode cap:valueNameactioncap:valueName cap:valueINSERTcap:value cap:eventCode cap:effective2010-06-03T20:56:41-05:00cap:effective cap:senderNameCuebWerx Inc.cap:senderName cap:headlineNew Feature Availablecap:headline cap:descriptionA new feature with identifier CWFID.BUILDINGGEOSURFACE.0.326 has been processed by the GSS and is now available.cap:description cap:instructionThe new feature can be retrieved by following the uri for the Feature Type resource. The WFS transaction that created the feature can be obtained by following the uri for the ATOM entry resource and reading the content of the entry.cap:instruction cap:resource cap:resourceDescATOM entrycap:resourceDesc cap:mimeTypeapplicationatom+xmlcap:mimeType cap:urihttp:www.cubewerx.comows7cubeservcubeserv.cgi?service=GSSamp;request=GetEn triedamp;id=urn:uuid:8084a1cd-50c6-49b1-9641-96241ad5dd1ecap:uri cap:resource cap:resource cap:resourceDescFeature Typecap:resourceDesc cap:mimeTypeapplicationgml+xml; version-3.1.1cap:mimeType cap:urihttp:www.pvretano.comngacubeserv.cgi?service=WFSamp;CONFIG=plugweekamp;DAT ASTORE=tdsamp;request=GetFeatureamp;typeName=BUILDINGGEOSURFACEamp;featureId=CWFID.BUI LDINGGEOSURFACE.0.326cap:uri cap:resource cap:area cap:polygon18.5778097 -72.2787128 18.5778097 -72.2787692 18.5778911 - 72.2787692 18.5778936 -72.2788604 18.5777792 -72.2788631 18.5777741 -72.2787128 18.5778097 -72.2787128cap:polygon cap:area cap:info cap:alert

12.2.9.9 Filtering CAP messages

As illustrated in Listing 6 and section 12.2.9.8, a CAP message is composed of values that are encoded in-line in the alert, info and area segments and of values that may be remotely references in the resource segment. Filtering CAP messages using FES to constrain in-line values is straight forward and does not present any technical challenges. In fact, CAP and FES work quite well together especially because CAP messages are spatio-temporally enabled thus allowing the spatial and temporal operators defined in FES to be used in query predicates when geometric location tagging is used. Of course, there is the issue of converting the CAP geometry to GML see 12.2.9.3 but this is more a nuisance than a show stopper.