# gml:Value

This is a convenience choice group which unifies generic values defined in this Clause with spatial and temporal objects and the measures described above, so that any of these may be used within aggregate values.

## Group information

Namespace: http://www.opengis.net/gml/3.2

Schema document: external/ogc/gml/3.2.1/valueObjects.xsd

## Content

- Choice [1..1]
- gml:Boolean
- gml:Category A gml:Category has an optional XML attribute codeSpace, whose value is a URI which identifies a dictionary, codelist or authority for the term.
- gml:Count
- gml:Quantity An XML attribute uom ("unit of measure") is required, whose value is a URI which identifies the definition of a ratio scale or units by which the numeric value shall be multiplied, or an interval or position scale on which the value occurs.
- gml:CompositeValue gml:CompositeValue is an aggregate value built from other values . It contains zero or an arbitrary number of gml:valueComponent elements, and zero or one gml:valueComponents property elements. It may be used for strongly coupled aggregates (vectors, tensors) or for arbitrary collections of values.
- gml:ValueArray A Value Array is used for homogeneous arrays of primitive and aggregate values. The member values may be scalars, composites, arrays or lists. ValueArray has the same content model as CompositeValue, but the member values shall be homogeneous. The element declaration contains a Schematron constraint which expresses this restriction precisely. Since the members are homogeneous, the gml:referenceSystem (uom, codeSpace) may be specified on the gml:ValueArray itself and inherited by all the members if desired.
- gml:CategoryExtent
- gml:CountExtent
- gml:QuantityExtent
- gml:MultiGeometry gml:MultiGeometry is a collection of one or more GML geometry objects of arbitrary type. The members of the geometric aggregate may be specified either using the "standard" property (gml:geometryMember) or the array property (gml:geometryMembers). It is also valid to use both the "standard" and the array properties in the same collection.
- gml:MultiPoint A gml:MultiPoint consists of one or more gml:Points. The members of the geometric aggregate may be specified either using the "standard" property (gml:pointMember) or the array property (gml:pointMembers). It is also valid to use both the "standard" and the array properties in the same collection.
- gml:MultiCurve A gml:MultiCurve is defined by one or more gml:AbstractCurves. The members of the geometric aggregate may be specified either using the "standard" property (gml:curveMember) or the array property (gml:curveMembers). It is also valid to use both the "standard" and the array properties in the same collection.
- gml:MultiSurface A gml:MultiSurface is defined by one or more gml:AbstractSurfaces. The members of the geometric aggregate may be specified either using the "standard" property (gml:surfaceMember) or the array property (gml:surfaceMembers). It is also valid to use both the "standard" and the array properties in the same collection.
- gml:MultiSolid A gml:MultiSolid is defined by one or more gml:AbstractSolids. The members of the geometric aggregate may be specified either using the "standard" property (gml:solidMember) or the array property (gml:solidMembers). It is also valid to use both the "standard" and the array properties in the same collection.
- gml:Point A Point is defined by a single coordinate tuple. The direct position of a point is specified by the pos element which is of type DirectPositionType.
- gml:LineString A LineString is a special curve that consists of a single segment with linear interpolation. It is defined by two or more coordinate tuples, with linear interpolation between them. The number of direct positions in the list shall be at least two.
- gml:CompositeCurve A gml:CompositeCurve is represented by a sequence of (orientable) curves such that each curve in the sequence terminates at the start point of the subsequent curve in the list. curveMember references or contains inline one curve in the composite curve. The curves are contiguous, the collection of curves is ordered. Therefore, if provided, the aggregationType attribute shall have the value "sequence".
- gml:Curve A curve is a 1-dimensional primitive. Curves are continuous, connected, and have a measurable length in terms of the coordinate system. A curve is composed of one or more curve segments. Each curve segment within a curve may be defined using a different interpolation method. The curve segments are connected to one another, with the end point of each segment except the last being the start point of the next segment in the segment list. The orientation of the curve is positive. The element segments encapsulates the segments of the curve.
- gml:OrientableCurve OrientableCurve consists of a curve and an orientation. If the orientation is "+", then the OrientableCurve is identical to the baseCurve. If the orientation is "-", then the OrientableCurve is related to another AbstractCurve with a parameterization that reverses the sense of the curve traversal.
- gml:Polygon A Polygon is a special surface that is defined by a single surface patch (see D.3.6). The boundary of this patch is coplanar and the polygon uses planar interpolation in its interior. The elements exterior and interior describe the surface boundary of the polygon.
- gml:CompositeSurface A gml:CompositeSurface is represented by a set of orientable surfaces. It is geometry type with all the geometric properties of a (primitive) surface. Essentially, a composite surface is a collection of surfaces that join in pairs on common boundary curves and which, when considered as a whole, form a single surface. surfaceMember references or contains inline one surface in the composite surface. The surfaces are contiguous.
- gml:Surface A Surface is a 2-dimensional primitive and is composed of one or more surface patches as specified in ISO 19107:2003, 6.3.17.1. The surface patches are connected to one another. patches encapsulates the patches of the surface.
- gml:PolyhedralSurface A polyhedral surface is a surface composed of polygon patches connected along their common boundary curves. This differs from the surface type only in the restriction on the types of surface patches acceptable. polygonPatches encapsulates the polygon patches of the polyhedral surface.
- gml:TriangulatedSurface A triangulated surface is a polyhedral surface that is composed only of triangles. There is no restriction on how the triangulation is derived. trianglePatches encapsulates the triangles of the triangulated surface.
- gml:Tin A tin is a triangulated surface that uses the Delauny algorithm or a similar algorithm complemented with consideration of stoplines (stopLines), breaklines (breakLines), and maximum length of triangle sides (maxLength). controlPoint shall contain a set of the positions (three or more) used as posts for this TIN (corners of the triangles in the TIN). See ISO 19107:2003, 6.4.39 for details.
- gml:OrientableSurface OrientableSurface consists of a surface and an orientation. If the orientation is "+", then the OrientableSurface is identical to the baseSurface. If the orientation is "-", then the OrientableSurface is a reference to a gml:AbstractSurface with an up-normal that reverses the direction for this OrientableSurface, the sense of "the top of the surface".
- gml:CompositeSolid gml:CompositeSolid implements ISO 19107 GM_CompositeSolid (see ISO 19107:2003, 6.6.7) as specified in D.2.3.6. A gml:CompositeSolid is represented by a set of orientable surfaces. It is a geometry type with all the geometric properties of a (primitive) solid. Essentially, a composite solid is a collection of solids that join in pairs on common boundary surfaces and which, when considered as a whole, form a single solid. solidMember references or contains one solid in the composite solid. The solids are contiguous.
- gml:Solid A solid is the basis for 3-dimensional geometry. The extent of a solid is defined by the boundary surfaces as specified in ISO 19107:2003, 6.3.18. exterior specifies the outer boundary, interior the inner boundary of the solid.
- gml:GeometricComplex
- gml:Grid The gml:Grid implicitly defines an unrectified grid, which is a network composed of two or more sets of curves in which the members of each set intersect the members of the other sets in an algorithmic way. The region of interest within the grid is given in terms of its gml:limits, being the grid coordinates of diagonally opposed corners of a rectangular region. gml:axisLabels is provided with a list of labels of the axes of the grid (gml:axisName has been deprecated). gml:dimension specifies the dimension of the grid. The gml:limits element contains a single gml:GridEnvelope. The gml:low and gml:high property elements of the envelope are each integerLists, which are coordinate tuples, the coordinates being measured as offsets from the origin of the grid along each axis, of the diagonally opposing corners of a "rectangular" region of interest.
- gml:RectifiedGrid A rectified grid is a grid for which there is an affine transformation between the grid coordinates and the coordinates of an external coordinate reference system. It is defined by specifying the position (in some geometric space) of the grid "origin" and of the vectors that specify the post locations. Note that the grid limits (post indexes) and axis name properties are inherited from gml:GridType and that gml:RectifiedGrid adds a gml:origin property (contains or references a gml:Point) and a set of gml:offsetVector properties.
- gml:TimeInstant gml:TimeInstant acts as a zero-dimensional geometric primitive that represents an identifiable position in time.
- gml:TimePeriod gml:TimePeriod acts as a one-dimensional geometric primitive that represents an identifiable extent in time. The location in of a gml:TimePeriod is described by the temporal positions of the instants at which it begins and ends. The length of the period is equal to the temporal distance between the two bounding temporal positions. Both beginning and end may be described in terms of their direct position using gml:TimePositionType which is an XML Schema simple content type, or by reference to an indentifiable time instant using gml:TimeInstantPropertyType. Alternatively a limit of a gml:TimePeriod may use the conventional GML property model to make a reference to a time instant described elsewhere, or a limit may be indicated as a direct position.
- gml:TimeNode A time node is a zero-dimensional topological primitive that represents an identifiable node in time (it is equivalent to a point in space). A node may act as the termination or initiation of any number of time edges. A time node may be realised as a geometry, its position, whose value is a time instant.
- gml:TimeEdge A time edge is a one-dimensional topological primitive. It is an open interval that starts and ends at a node. The edge may be realised as a geometry whose value is a time period.
- gml:TimeTopologyComplex A temporal topology complex shall be the connected acyclic directed graph composed of temporal topological primitives, i.e. time nodes and time edges. Because a time edge may not exist without two time nodes on its boundaries, static features have time edges from a temporal topology complex as the values of their temporal properties, regardless of explicit declarations. A temporal topology complex expresses a linear or a non-linear graph. A temporal linear graph, composed of a sequence of time edges, provides a lineage described only by "substitution" of feature instances or feature element values. A time node as the start or the end of the graph connects with at least one time edge. A time node other than the start and the end shall connect to at least two time edges: one of starting from the node, and another ending at the node. A temporal topological complex is a set of connected temporal topological primitives. The member primtives are indicated, either by reference or by value, using the primitive property.
- gml:Null deprecated

from subst. group gml:AbstractValuefrom subst. group gml:AbstractScalarValuefrom subst. group gml:AbstractScalarValueListfrom subst. group gml:CompositeValuefrom subst. group gml:AbstractGeometryfrom subst. group gml:AbstractGeometricAggregatefrom subst. group gml:AbstractGeometricPrimitivefrom subst. group gml:AbstractCurvefrom subst. group gml:AbstractSurfacefrom subst. group gml:Surfacefrom subst. group gml:TriangulatedSurfacefrom subst. group gml:AbstractSolidfrom subst. group gml:AbstractImplicitGeometryfrom subst. group gml:Gridfrom subst. group gml:AbstractTimeGeometricPrimitivefrom subst. group gml:AbstractTimeTopologyPrimitivefrom subst. group gml:AbstractTimeComplex

## Used in

- Type gml:ValueArrayPropertyType (Element gml:valueComponents)
- Type gml:ValuePropertyType (Elements gml:valueProperty, gml:valueComponent)