DiscreteCoverageType, AbstractDiscreteCoverage Coverage schema

206 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. The coverageFunction element describes the mapping ―f‖ as shown in Figure 4. The abstract element gml:AbstractDiscreteCoverage implements ISO 19123 CV_DiscreteCoverage see D.2.11 and ISO 19123:2005, 5.7 and is declared as follows: element name=AbstractDiscreteCoverage type=gml:DiscreteCoverageType abstract=true substitutionGroup=gml:AbstractCoverage This element serves as the head of a substitution group which may contain any discrete coverage.

19.3.3 AbstractContinuousCoverageType, AbstractContinuousCoverage

A continuous coverage as defined in ISO 19123 is a coverage that can return different values for the same feature attribute at different direct positions within a single spatiotemporal object in its spatiotemporal domain. The base type for continuous coverages is AbstractContinuousCoverageType, defined in the schema as follows: complexType name=AbstractContinuousCoverageType abstract=true complexContent extension base=gml:AbstractCoverageType sequence element ref=gml:coverageFunction minOccurs=0 sequence extension complexContent complexType The coverageFunction element describes the mapping ―f‖ as shown in Figure 4. The abstract element gml:AbstractContinuousCoverage is declared as follows: element name=AbstractContinuousCoverage type=gml:AbstractContinuousCoverageType abstract=true substitutionGroup=gml:AbstractFeature This element serves as the head of a substitution group which may contain any continuous coverage whose type is derived from gml:AbstractContinuousCoverageType.

19.3.4 domainSet, DomainSetType

The gml:domainSet property element describes the spatio-temporal region of interest, within which the coverage is defined. Its content model is given by gml:DomainSetType which is defined as follows: element name=domainSet type=gml:DomainSetType complexType name=DomainSetType sequence minOccurs=0 choice element ref=gml:AbstractGeometry element ref=gml:AbstractTimeObject choice sequence attributeGroup ref=gml:OwnershipAttributeGroup attributeGroup ref=gml:AssociationAttributeGroup complexType Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 207 The value of the domain is thus a choice between a gml:AbstractGeometry and a gml:AbstractTimeObject. In the instance these abstract elements will normally be substituted by a geometry complex or temporal complex, to represent spatial coverages and time-series, respectively. NOTE Spatiotemporal domains are supported if the domain is described using a compound coordinate reference system, one of whose components is temporal. Otherwise, following the ISO 19100 series of International Standards, GML does not support combined spatial-temporal domains. The presence of the gml:AssociationAttributeGroup means that domainSet follows the usual GML property model and may use the xlink:href attribute to point to the domain, as an alternative to describing the domain inline. Ownership semantics may be provided using the gml:OwnershipAttributeGroup.

19.3.5 rangeSet, RangeSetType

The gml:rangeSet property element contains the values of the coverage sometimes called the attribute values. Its content model is given by gml:RangeSetType which is defined as follows:: element name=rangeSet type=gml:RangeSetType complexType name=RangeSetType choice element ref=gml:ValueArray maxOccurs=unbounded element ref=gml:AbstractScalarValueList maxOccurs=unbounded element ref=gml:DataBlock element ref=gml:File choice complexType This content model supports a structural description of the range. The semantic information describing the range set is embedded using a uniform method, as part of the explicit values, or as a template value accompanying the representation using gml:DataBlock and gml:File. The values from each component or ―band‖ in the range may be encoded within a gml:ValueArray element or a concrete member of the gml:AbstractScalarValueList substitution group 7 . Use of these elements satisfies the value-type homogeneity requirement.

19.3.6 DataBlock

gml:DataBlock describes the Range as a block of text encoded values similar to a Common Separated Value CSV representation. The content model is as follows: element name=DataBlock type=gml:DataBlockType substitutionGroup=gml:AbstractObject complexType name=DataBlockType sequence element ref=gml:rangeParameters choice element ref=gml:tupleList element ref=gml:doubleOrNilReasonTupleList choice sequence complexType 7 e.g. gml:CategoryList, gml:QuantityList — see 16.4.