SWE Common AIXM Information models

Copyright © 2010 Open Geospatial Consortium, Inc. 117

12.2.8 WXXM

The Weather Information Exchange Model is also based on XML. It is used to encode weather observations current observations and forecasts. These are represented as an extension of OM observations. In version 1.1 it uses OM version 1.0.1 to be compatible to the AIXM which relies on GML 3.2.1. It is usable in the same way as OM for the encoding of events but adds additional properties that help to filter on properties that are of special interest in the aviation domain.

12.2.9 Common Alert Protocol

12.2.9.1 Introduction

The Common Alert Protocol CAP is a message format for encoding alert or notification messages. The main idea of CAP is to normalize the expression of alert messages arising from various sources. Such normalization then allows these messages to be aggregated and compared to aid situational awareness and pattern detection. To that end, the CAP standard describes a document object model that defines the structure of an alert or notification messages and a protocol that describes how CAP messages should be constructed, used and related to each other. The CAP standard also describes a concrete implementation of its document model using XML and expressed in XML-Schema. A limited amount of testing was done by CubeWerx Inc during the OWS-7 test bed with CAP v1.1 and the Geosynchronization service. That work involved generating CAP messages as notification messages sent to subscribers. So rather than sending subscribers ATOM entries, the format used in the GSS specification, CAP messages were generated and sent instead. Unfortunately, it was not possible in the time frame of the project to also test filtering of CAP message using the Filter encoding specification as was done with ATOM entries so any discussion about using FES with CAP is purely notional.

12.2.9.2 Document object model

Figure 42 illustrates the UML definition of a CAP message. 118 Copyright © 2010 Open Geospatial Consortium, Inc. Figure 42: UML for CAP Message The model defines four primary segments: alert , info , resource and area . The alert segment provides basic information about the message: purpose, source, status, etc. The alter segment can be used alone for message acknowledgements, cancellations and other system functions. The info segment encodes the details of the alert. Multiple info segments can be included to express information in multiple languages or across multiple disconnected areas. The resource segment provides an optional reference to additional related resources. The area segment describes the geographic area to which the notification applies.

12.2.9.3 Spatially enabled

CAP is spatially enabled allowing messages to be targeted geographically.