Relationship with ISO 19111 Important XML elements

98 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. The concrete XML elements that are substitutable for SingleCRS use multiple lower-level XML elements containing data structures. These lower-level elements include all five concrete elements that are substitutable for the abstract Datum XML element, named:  GeodeticDatum  VerticalDatum  TemporalDatum  EngineeringDatum  ImageDatum These lower-level XML elements also include all ten concrete elements that are substitutable for the abstract CoordinateSystem XML element, named:  EllipsoidalCS  VerticalCS  CartesianCS  AffineCS  LinearCS  PolarCS  SphericalCS  CylindricalCS  TimeCS  UserDefinedCS The concrete XML elements that are substitutable for the CoordinateOperation element use multiple lower-level elements containing data structures, including the elements named:  OperationMethod  OperationParameter  OperationParameterGroup  ParameterValue  ParameterValueGroup Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 99

12.2 Reference systems

12.2.1 Overview

The reference systems schema components have two logical parts, which define elements and types for XML encoding of the definitions of:  Identified Object, inherited by the ten types of GML object used for coordinate reference systems and coordinate operations  High-level part of the definitions of coordinate reference systems This schema encodes the Identified Object and Reference System packages of the UML Model for ISO 19111. NOTE The referenceSystems schema includes the dictionary.xsd GML schema document, and imports the metadataEntitySet.xsd schema document from ISO 19139. This schema document is identified by the following location- independent name using URN syntax: urn:x-ogc:specification:gml:schema-xsd:referenceSystems:3.2.1

12.2.2 IdentifiedObjectType

complexType name=IdentifiedObjectType abstract=true complexContent extension base=gml:DefinitionType complexContent complexType gml:IdentifiedObjectType provides identification properties of a CRS-related object. In gml:DefinitionType, the gml:identifier element shall be the primary name by which this object is identified, encoding the name attribute in the UML model. Zero or more of the gml:name elements can be an unordered set of identifiers, encoding the identifier attribute in the UML model. Each of these gml:name elements can reference elsewhere the objects defining information or be an identifier by which this object can be referenced. Zero or more other gml:name elements can be an unordered set of alias alternative names by which this CRS related object is identified, encoding the alias attributes in the UML model. An object may have several aliases, typically used in different contexts. The context for an alias is indicated by the value of its optional codeSpace attribute. Any needed version information shall be included in the codeSpace attribute of a gml:identifier and gml:name elements. In this use, the gml:remarks element in the gml:DefinitionType shall contain comments on or information about this object, including data source information. 12.2.3 Abstract coordinate reference system 12.2.3.1 AbstractCRS element name=AbstractCRS type=gml:AbstractCRSType abstract=true substitutionGroup=gml:Definition complexType name=AbstractCRSType abstract=true complexContent extension base=gml:IdentifiedObjectType sequence 100 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. element ref=gml:domainOfValidity minOccurs=0 maxOccurs=unbounded element ref=gml:scope maxOccurs=unbounded sequence extension complexContent complexType gml:AbstractCRS specifies a coordinate reference system which is usually single but may be compound. This abstract complex type shall not be used, extended, or restricted, in a GML application schema, to define a concrete subtype with a meaning equivalent to a concrete subtype specified in this document.

12.2.3.2 domainOfValidity

element name=domainOfValidity complexType sequence minOccurs=0 element ref=gmd:EX_Extent sequence attributeGroup ref=gml:AssociationAttributeGroup complexType element The gml:domainOfValidity property implements an association role to an EX_Extent object as encoded in ISOTS 19139, either referencing or containing the definition of that extent.

12.2.3.3 scope

element name=scope type=string The gml:scope property provides a description of the usage, or limitations of usage, for which this CRS-related object is valid. If unknown, enter not known.

12.2.3.4 CRSPropertyType

complexType name=CRSPropertyType sequence minOccurs=0 element ref=gml:AbstractCRS sequence attributeGroup ref=gml:AssociationAttributeGroup complexType gml:CRSPropertyType is a property type for association roles to a CRS abstract coordinate reference system, either referencing or containing the definition of that CRS.

12.3 Coordinate reference systems

12.3.1 Overview

The spatial-temporal coordinate reference systems schema components are divided into two logical parts. One part defines elements and types for XML encoding of abstract coordinate reference systems definitions. The larger part defines specialized constructs for XML encoding of definitions of the multiple concrete types of spatial- temporal coordinate reference system.