User-defined coverage types Schemas defining coverages

Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 235 NOTE 2 This International Standard provides the concrete coverage types gml:MultiPointCoverage, gml:MultiCurveCoverage, gml:MultiSurfaceCoverage, gml:MultiSolidCoverage, gml:GridCoverage, and gml:RectifiedGridCoverage. Application coverages may derive from any of these as well. Any user-defined coverage subtype shall inherit the elements and attributes of the base GML coverage types without restriction, but may extend these base types to meet application requirements, such as providing a finer degree of interoperability with legacy systems and data sets. All rules specified in Clauses 7, 9 and 19 shall be followed.

21.8.4 Range parameters shall be substitutable for AbstractValue

The coverage application schema shall define or import the definitions for all range parameters. Each such range parameter shall be substitutable for gml:AbstractValue as defined in 16.4. Note that this allows the range parameter to take on a wide range of types. Note further that the schema components specified in 16.4 include several abstract subtypes that are substitutable for gml:AbstractValue, including gml:AbstractScalarValue and gml:AbstractValueList. Concrete scalar and value list types, and substitution group head elements, are also provided substitutable for gml:AbstractScalarValue or gml:AbstractValueList and include:  gml:Category the content model is specified by gml:CodeType  gml:CategoryList the content model is specified by gml:CodeOrNilReasonListType  gml:Quantity the content model is specified by gml:MeasureType  gml:QuantityList the content model is specified by gml:MeasureOrNilReasonListType  gml:Count the content model is specified by gml:CountType  gml:Boolean the content model is specified by gml:BooleanType To define the range parameters in a Coverage Application Schema, refer to 16.4. EXAMPLE Typical examples of the use of the value types in the development of a GML coverage can be found in 19.3, and are summarized in Table 8. 236 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. Table 8 — Range parameters for coverage schemas Coverage Range parameter Definition in GML Temperature Distribution weather Temperature Would be derived from gml:MeasureOrNilReasonListType and made substitutable for gml:measure defined in 16.3.2. Soil type distribution agronomy Soil type Would be derived from gml:CategoryType and made substitutable for gml:Category. Weak reference to an enumeration of soil types. Multi-spectral optical image remote sensing Reflectance in each spectral band. Would be derived from gml:QuantityListType and made substitutable for gml:QuantityList. Distribution of West Nile Virus cases. epidemiology CaseCount Would be derived from gml:integerOrNilReasonList, and made substitutable for gml:CountList.

21.8.5 Coverage document

A coverage document is defined by a corresponding coverage schema. The root element of this document shall be a coverage defined in this schema or may be a feature collection as described in 9.9 whose members are coverages.

21.9 Schemas defining observations

21.9.1 Introduction

The following subclauses describe how to create an observation application schema. Observations are described in Clause 18. An observation application schema defines one or more types of observation in accordance with the following rules.

21.9.2 Import GML observation schema components

The application schema shall import the GML schema as described in 21.2.3. Any GML profile referenced from the application schema shall include at least the gml:Observation element and all schema components used by this element.

21.9.3 User-defined observation types

All observation types defined in the GML application schema shall be declared as global elements in the schema, i.e. they shall be child elements of the XML Schema schema element. The content model for such global elements shall derive by extension either directly or indirectly from gml:ObservationType. Authors of application schemas may create their own observation types if GML lacks the desired construct. To do this, authors shall ensure that the object elements of these observation types are in the substitution group either directly or indirectly of the corresponding GML object element: gml:Observation. NOTE 1 These elements are indirectly in the substitution group of gml:AbstractFeature and hence the condition of the feature model is satisfied. NOTE 2 This International Standard provides the concrete simple observation types gml:Observation, gml:DirectedObservation and gml:DirectedObservationAtDistance. Application observation types may derive from any of these as well. All rules specified in Clauses 7, 9 and 18 shall be followed.