MultiSolidCoverage GridCoverage Coverage schema

220 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. Figure 8 — Grid coverage domain is a grid of points element name=GridCoverage type=gml:DiscreteCoverageType substitutionGroup=gml:AbstractDiscreteCoverage Note that this is the same as the gml:MultiPointCoverage except that the value in gml:domainSet shall be a gml:Grid. gml:Grid is defined in 19.2.2. Note that the simple grid coverage is not geometrically referenced and hence no geometric positions are assignable to the points in the grid. Such geometric positioning is introduced in the gml:RectifiedGridCoverage discussed in 19.3.21. NOTE When a grid point is used to represent a sample space, the grid point represents the center of the sample space, see 19.2.2. EXAMPLE A gml:GridCoverage using a file encoding for its values: AverageTempPressure gml:domainSet gml:Grid dimension=2 gml:limits gml:GridEnvelope gml:low0 0gml:low gml:high4 4gml:high gml:GridEnvelope gml:limits gml:axisLabelsx ygml:axisLabels gml:Grid gml:domainSet gml:rangeSet gml:File gml:rangeParameters gml:CompositeValue gml:valueComponents Temperature uom=urn:x-si:v1999:uom:degreesCtemplateTemperature Pressure uom=urn:x-si:v1999:uom:kPatemplatePressure gml:valueComponents gml:CompositeValue gml:rangeParameters gml:fileReferencehttp:www.somedata.orgtemp_pressure.datgml:fileReference gml:fileStructureRecord Interleavedgml:fileStructure gml:File gml:rangeSet AverageTempPressure Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 221

19.3.21 RectifiedGridCoverage

The gml:RectifiedGridCoverage is a discrete point coverage based on a rectified grid. It is similar to the grid coverage of 19.3.20 except that the points of the grid are geometrically referenced. The rectified grid coverage has a domain that is a gml:RectifiedGrid geometry as defined in 19.2.3. element name=RectifiedGridCoverage type=gml:DiscreteCoverageType substitutionGroup=gml:AbstractDiscreteCoverage The value in gml:domainSet shall be a gml:RectifiedGrid. gml:RectifiedGrid is defined in 19.2.3. EXAMPLE A gml:RectifiedGridCoverage using a data block: AveragePressure xmlns=http:www.opengis.netapp xmlns:gml=http:www.opengis.netgml3.2 xmlns:xsi=http:www.w3.org2001XMLSchema-instance xsi:schemaLocation=http:www.opengis.netapp .CoverageExamples.xsd gml:boundedBy gml:Envelope srsName=urn:x-ogc:def:crs:EPSG:6.6:4329 gml:lowerCorner1.2 3.3 2.1gml:lowerCorner gml:upperCorner13.6 12.1 15.3gml:upperCorner gml:Envelope gml:boundedBy gml:domainSet gml:RectifiedGrid dimension=2 gml:limits gml:GridEnvelope gml:low1 1gml:low gml:high4 4gml:high gml:GridEnvelope gml:limits gml:axisLabelsu vgml:axisLabels gml:origin gml:Point gml:id=palindrome srsName=urn:x-ogc:def:crs:EPSG:6.6:4329 gml:pos1.2 3.3 2.1gml:pos gml:Point gml:origin gml:offsetVector srsName=urn:x-ogc:def:crs:EPSG:6.6:43291.1 2.2 3.3gml:offsetVector gml:offsetVector srsName=urn:x-ogc:def:crs:EPSG:6.6:43292.0 1.0 0.0gml:offsetVector gml:RectifiedGrid gml:domainSet gml:rangeSet gml:DataBlock gml:rangeParameters Pressure uom=urn:x-si:v1999:uom:kPatemplatePressure gml:rangeParameters gml:doubleOrNilReasonTupleList101.2 101.3 101.4 101.5 101.6 101.7 101.7 101.8 101.9 102.0 102.1 102.2 102.3 102.4 102.5 102.6gml:doubleOrNilReasonTupleList gml:DataBlock gml:rangeSet AveragePressure 222 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 20 Profiles

20.1 Profiles of GML and application schemas

GML is a complex standard that is richly expressive. In general, an application need not exploit the entire GML schema, but may employ a subset of constructs corresponding to specific relevant requirements. We use this definition of a profile ISOIEC TR 10000-1:1998 and ISO 19106:2004: Profile: A set of one or more base standards andor [profiles], and, where applicable, the identification of chosen classes [types, attributes and elements], conforming subsets, options and parameters of those base standards, or [profiles] necessary to accomplish a particular function. This was defined for an OSI architecture model, so we translate ‗class‘ to ‗types, attributes and elements‘ to apply this definition to XML Schema . There are several ways to implement this, and GML profiles use a ―copy and delete‖ approach. To create a profile, a developer might copy the applicable schema files from GML and simply delete any global types, elements and local optional particles that she does not need for her application schema.

20.2 Definition of profile

A profile of GML may be defined to enhance interoperability and to curtail ambiguity by allowing only a specific subset of GML. Application schemas may then conform to such a profile in order to take advantage of any interoperability or performance advantages that it offers in comparison with a complete GML. Such profiles may be defined for application schemas that are included in other specifications. There are cases where reduced functionality is acceptable, or where processing requirements compel use of a logical subset of GML. For example, applications that do not need to handle XLink attributes in any form may adhere to a specific profile that excludes them; the constraint in this case would be to not use links. Other cases might include defining constraints on the level of nesting allowed inside tags i.e. tree depth, or only allowing features with homogeneous properties as members of a feature collection. In many cases, such constraints may be enforced via new schemas; others may be enforced through procedural agreements within an information community.

20.3 Relation to application schema

A profile may be the beginning of an application schema. EXAMPLE A location based service profile may limit the types of geometry to that used in LBS applications, and the LBS application schema may then add a ―PointCircle,‖ ―PointEllipse‖ and ―PointArc‖ elements to accommodate the LIF ―CIRCLE,‖ ―ELLIPSE‖ and ―ARC‖ elements, which are used to describe error estimates of mobile device location. The building of such application schemas is thus a two-part process. The profile acts as a restriction of GML to produce types and elements consistent with the complete GML but potentially lacking in some optional particles. The application schema then uses these types as a common base, and uses them in new types and elements by extensions or inclusion. GML  selection restriction  GML profile  extension inclusion  application schema

20.4 Rules for elements and types in a profile

Global profiled elements in a GML profile shall:  share the same name and namespace of a parent element in GML.