This section gives a general description of the METCE-XML and IWXXM-XML schemas and their associated XML-Java bindings, how the latter can be used to encode OPMET (OPerational METeorological) data for aviation (namely METAR/SPECI, TAF and SIGMET) and validation of the products against the format and other constraints described by the XML schemas.

Location and Structure of METCE-XML and IWXXM-XML Schemas

As of Version 1.0, METCE-XML and IWXXM-XML schemas are co-located at the WMO website http://schema.wmo.int with the following directory structure:

Packages	Location on schemas.wmo.int
OPM-XML	http://schemas.wmo.int	/wmo	/opm/1.0	/observable-property.xsd /opm.xsd
METCE-XML			/metce/1.0	/metce.xsd /phenomena.xsd /procedure.xsd
SAF-XML		/icao	/saf/1.0	/dataTypes.xsd /features.xsd /measures.xsd /saf.xsd
IWXXM-XML			/iwxxm/1.0	/common.xsd /iwxxm.xsd /metarSpeci.xsd /sigmet.xsd /taf.xsd
External Schematron Rules		/rule	/1.0	/iwxxm.sch /metce.sch /opm.sch /saf.sch

These XSD files are generated by semi-automatic processes from their respective models in UML with manual addition of embedded schematron rules. The schematron rules are also distributed as separate files to facilitate execution with certain validators. A compressed zip file 'AvXML-1.0-schema.zip' containing all of the above is available _HERE_ on the WMO WIS-WIKI.

Creation of XML Instances

While there is no requirement to use a specific software to prepare XML instances, an XML editor like '<oXygen/> XML Editor' will provide real time checking of the XML instances against the XML schemas during manual input. To facilitate the development of automatic software to generate XML instances, an XML-Java binding ‘AvXML-1.0.jar’ is also made available for download _HERE_ at the WMO WIS-WIKI. Created with XMLBeans, one can access instances of the METCE-XML and IWXXM-XML schemas through JavaBeans-style accessors. See documentation of XMLBeans for details. A sample program using the XML-Java binding and the respective XML instance generated can be downloaded _HERE_.

For descriptions of the elements and attributes of individual XSD files one should refer to the documentation of the UML models _HERE_ on the WMO WIS-WIKI.

Validation of XML Instances against AvXML Schemas

The following shows the process of validating an XML instance with METCE-XML and IWXXM-XML schemas using '<oXygen/> XML Editor'. Please be advised that the location of METCE-XML and IWXXM-XML schemas has to be explicitly specified so as to tell the XML Editor the place to obtain the embedded schematrons for validation.

Known Issues

Certain constraints as shown in the UML models have not been implemented. They will be handled in subsequent releases of the schemas.