GML Subset schema for gml:_Feature,gml:_FeatureCollection,gml:FeatureCollection,gml:_Coverage,gml:RectifiedGridCoverage,gml:MeasureOrNullListType,gml:Point,gml:LineString,gml:Polygon,gml:LinearRing,gml:Dictionary,gml:_Definition,gml:dictionaryEntry,gml:Dictionary,gml:BaseUnit,gml:ConventionalUnit,gml:DerivedUnit,gml:ProjectedCRS,gml:Conversion,gml:GeographicCRS,gml:centerLineOf,gml:extentOf,gml:QuantityList,gml:GeometryPropertyType,gml:PolygonPropertyType,gml:defaultStyle,gml:MultiSurface,gml:Style,gml:_MetaData, written by gmlSubset.xslt. An abstract feature provides a set of common properties, including id, metaDataProperty, name and description inherited from AbstractGMLType, plus boundedBy. A concrete feature type shall derive from this type and specify additional properties in an application schema. A feature shall possess an identifying attribute ('id' - 'fid' has been deprecated). deprecated deprecated in GML version 3.1 All complexContent GML elements are directly or indirectly derived from this abstract supertype establish a hierarchy of GML types that may be distinguished from other XML types by their ancestry. in this hierarchy may have an ID and are thus referenceable. This content model group makes it easier to construct types that derive from AbstractGMLType and its descendents "by restriction". A reference to the group saves having to enumerate the standard object properties. Multiple names may be provided. These will often be distinguished by being assigned by different authorities, as indicated by the value of the codeSpace attribute. In an instance document there will usually only be one name per authority. Contains or refers to a metadata package that contains metadata properties. Base type for complex metadata property types. Attribute group used to enable property elements to refer to their value remotely. It contains the simple link components from xlinks.xsd, with all members optional, and the remoteSchema attribute, which is also optional. These attributes can be attached to any element, thus allowing it to act as a pointer. The 'remoteSchema' attribute allows an element that carries link attributes to indicate that the element is declared in a remote schema rather than by the schema that constrains the current document instance. Reference to an XML Schema fragment that specifies the content model of the propertys value. This is in conformance with the XML Schema Section 4.14 Referencing Schemas from Elsewhere. Contains a simple text description of the object, or refers to an external description. type is available wherever there is a need for a "text" type property. It is of string type, so the text can be included inline, but the value can also be referenced remotely via xlinks from the AssociationAttributeGroup. If the remote reference is present, then the value obtained by traversing the link should be used, and the string content of the element can be used for an annotation. Label for the object, normally a descriptive name. An object may have several names, typically assigned by different authorities. The authority for a name is indicated by the value of its (optional) codeSpace attribute. The name may or may not be unique, as determined by the rules of the organization responsible for the codeSpace. Name or code with an (optional) authority. Text token. If the codeSpace attribute is present, then its value should identify a dictionary, thesaurus or authority for the term, such as the organisation who assigned the value, or the dictionary from which it is taken. A text string with an optional codeSpace attribute. Database handle for the object. It is of XML type ID, so is constrained to be unique in the XML document within which it occurs. An external identifier for the object in the form of a URI may be constructed using standard XML and XPointer methods. This is done by concatenating the URI for the document, a fragment separator, and the value of the id attribute. Bounding shape. Envelope defines an extent using a pair of positions defining opposite corners in arbitrary dimensions. The first direct is the "lower corner" (a coordinate position consisting of all the minimal ordinates for each dimension for all points within the envelope), second one the "upper corner" (a coordinate position consisting of all the maximal ordinates for each dimension for all points within the ). deprecated deprecated with GML version 3.0 deprecated Deprecated with GML version 3.1. Use the explicit properties "lowerCorner" and "upperCorner" instead. Deprecated with GML version 3.1.0. Use the explicit properties "lowerCorner" and "upperCorner" instead. DirectPosition instances hold the coordinates for a position within some coordinate reference system (CRS). Since , as data types, will often be included in larger objects (such as geometry elements) that have references to CRS, the "srsName" attribute will in general be missing, if this particular DirectPosition is included in a larger element with such a reference to a . In this case, the CRS is implicitly assumed to take on the value of the containing object's CRS. XML List based on XML Schema double type. An element of this type contains a space-separated list of double values Optional reference to the CRS used by this geometry, with optional additional information to simplify use when more complete definition of the CRS is not needed. In general this reference points to a CRS instance of gml:CoordinateReferenceSystemType (see coordinateReferenceSystems.xsd). For well known references it is not required that the CRS description exists at the the URI points to. If no srsName attribute is given, the CRS shall be specified as part of the larger context this element is part of, e.g. a geometric element like point, curve, etc. It is expected that this attribute will be specified the direct position level only in rare cases. The "srsDimension" is the length of coordinate sequence (the number of entries in the list). This dimension is by the coordinate reference system. When the srsName attribute is omitted, this attribute shall be omitted. Optional additional and redundant information for a CRS to simplify use when a more complete definition of the is not needed. This information shall be the same as included in the more complete definition of the CRS, referenced by the attribute. When the srsName attribute is included, either both or neither of the axisLabels and uomLabels attributes be included. When the srsName attribute is omitted, both of these attributes shall be omitted. Ordered list of labels for all the axes of this CRS. The gml:axisAbbrev value should be used for these axis , after spaces and forbiddden characters are removed. When the srsName attribute is included, this attribute is optional. the srsName attribute is omitted, this attribute shall also be omitted. Ordered list of unit of measure (uom) labels for all the axes of this CRS. The value of the string in the :catalogSymbol should be used for this uom labels, after spaces and forbiddden characters are removed. When the attribute is included, this attribute shall also be included. When the axisLabels attribute is omitted, this attribute also be omitted. A set of values, representing a list of token with the lexical value space of NCName. The tokens are seperated by whitespace. Deprecated with GML 3.0 and included for backwards compatibility with GML 2. Use the "pos" element instead. Represents a coordinate tuple in one, two, or three dimensions. Deprecated with GML 3.0 and replaced by . Deprecated with GML version 3.1.0. Tables or arrays of tuples. May be used for text-encoding of values from a table. Actually just a string, but allows the user to indicate which characters are used as separators. The value of the 'cs' attribute is the separator for coordinate values, and the value of the 'ts' attribute gives the tuple separator (a single space by default); the default values may be changed to reflect local usage. Defaults to CSV within a tuple, space between tuples. However, any string content will be schema-valid. Utility type for null elements. The value may be selected from one of the enumerated tokens, or may be a URI in which case this should identify a resource which describes the reason for the null. Some common reasons for a null value: innapplicable - the object does not have a value missing - The correct value is not readily available to the sender of this data. Furthermore, a correct value may not exist. template - the value will be available later unknown - The correct value is not known to, and not computable by, the sender of this data. However, a correct value probably exists. withheld - the value is not divulged other:reason - as indicated by "reason" string Specific communities may agree to assign more strict semantics when these terms are used in a particular context. Deprecated in GML 3.1.0 Convenience property for generalised location. A representative location for plotting or analysis. Often augmented by one or more additional geometry properties with more specific semantics. Deprecated in GML 3.1.0 The "_Geometry" element is the abstract head of the substituition group for all geometry elements of GML 3. This pre-defined and user-defined geometry elements. Any geometry element shall be a direct or indirect extension/restriction AbstractGeometryType and shall be directly or indirectly in the substitution group of "_Geometry". All geometry elements are derived directly or indirectly from this abstract supertype. A geometry element may an identifying attribute ("gml:id"), a name (attribute "name") and a description (attribute "description"). It may be associated a spatial reference system (attribute "srsName"). The following rules shall be adhered: - Every geometry type shall derive this abstract type. - Every geometry element (i.e. an element of a geometry type) shall be directly or indirectly in the group of _Geometry. This attribute is included for backward compatibility with GML 2 and is deprecated with GML 3. identifer is superceded by "gml:id" inherited from AbstractGMLType. The attribute "gid" should not be used and may be deleted in future versions of GML without further notice. Global element which acts as the head of a substitution group that may include any element which is a GML feature, object, geometry or complex value This abstract element is the head of a substitutionGroup hierararchy which may contain either simpleContent or complexContent elements. It is used to assert the model position of "class" elements declared in other GML schemas. A feature collection contains zero or more features. Container for a feature - follow gml:AssociationType pattern. Container for features - follow gml:ArrayAssociationType pattern. Concrete generic feature collection. Abstract element which acts as the head of a substitution group for coverages. Note that a coverage is a GML feature. The spatiotemporal domain of a coverage. Typically * a geometry collection, * an implicit geometry (e.g. a grid), * an explicit or implicit collection of time instances or periods, or .B. Temporal geometric complexes and temporal grids are not yet implemented in GML. This abstract element acts as the head of the substitution group for temporal primitives and complexes. The abstract supertype for temporal objects. each member _Value holds a tuple or "row" from the equivalent table each list holds the complete set of one scalar component from the values - i.e. a "column" from the equivalent table Its tuple list holds the values as space-separated tuples each of which contains comma-separated components, and the tuple structure is specified using the rangeParameters property. a reference to an external source for the data, together with a description of how that external source is structured ValueArray may not carry both a reference to a codeSpace and a uom All components of shall be of the same type All components of shall be of the same type A Value Array is used for homogeneous arrays of primitive and aggregate values. _ScalarValueList is preferred for arrays of Scalar Values since this is more efficient. Since "choice" is not available for attribute groups, an external constraint (e.g. Schematron) would be required to enforce the selection of only one of these through schema validation 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 referenceSystem (uom, codeSpace) may be specified on the ValueArray itself and implicitly inherited by all the members if desired. Note that a_ScalarValueList is preferred for arrays of Scalar Values since this is a more efficient encoding. Aggregate value built from other Values using the Composite pattern. It contains zero or an arbitrary number of valueComponent elements, and zero or one valueComponents elements. It may be used for strongly coupled aggregates (vectors, tensors) or for arbitrary collections of values. Element which refers to, or contains, a Value. This version is used in CompositeValues. GML property which refers to, or contains, a Value Utility choice group which unifies generic Values defined in this schema document with and Temporal objects and the Measures described above, that any of these may be used within aggregate Values. A value from two-valued logic, using the XML Schema boolean type. An instance may take the values {true, false, 1, 0}. A term representing a classification. It has an optional XML attribute codeSpace, whose value is a URI which identifies a dictionary, codelist or authority for the term. A numeric value with a scale. The content of the element is an amount using the XML Schema type double which permits decimal or scientific notation. An XML attribute uom (unit of measure) is required, whose value is a URI which identifies the definition of the scale or units by which the numeric value shall be multiplied. Number with a scale. The value of uom (Units Of Measure) attribute is a reference to a Reference System for the amount, either a ratio or position scale. An integer representing a frequency of occurrence. XML List based on XML Schema boolean type. An element of this type contains a space-separated list of boolean values {0,1,true,false} XML List based on the union type defined above. An element declared with this type contains a space-separated list of boolean values {0,1,true,false} with null values interspersed as needed Union of the XML Schema boolean type and the GML Nulltype. An element which uses this type may have content which is either a boolean {0,1,true,false} or a value from Nulltype A space-separated list of terms or nulls. A single XML attribute codeSpace may be provided, which authorises all the terms in the list. List of values on a uniform nominal scale. List of text tokens. In a list context a token should not include any spaces, so xsd:Name is used instead of xsd:string. A member of the list may be a typed null. If a codeSpace attribute is present, then its value is a reference to a Reference System for the value, a dictionary or code list. XML List based on the union type defined above. An element declared with this type contains a space-separated list of Name values with null values interspersed as needed Union of the XML Schema Name type and the GML Nulltype. An element which uses this type may have content which is either a Name or a value from Nulltype. Note that a "Name" may not contain whitespace. A space separated list of amounts or nulls. The amounts use the XML Schema type double. A single XML attribute uom (unit of measure) is required, whose value is a URI which identifies the definition of the scale or units by which all the amounts in the list shall be multiplied. List of numbers with a uniform scale. A member of the list may be a typed null. The value of uom (Units Of Measure) attribute is a reference to a Reference System for the amount, either a ratio or position scale. XML List based on the union type defined above. An element declared with this type contains a space-separated list of double values with null values interspersed as needed Union of the XML Schema double type and the GML Nulltype. An element which uses this type may have content which is either a double or a value from Nulltype A space-separated list of integers or nulls. XML List based on the union type defined above. An element declared with this type contains a space-separated list of integer values with null values interspersed as needed Union of the XML Schema integer type and the GML Nulltype. An element which uses this type may have content which is either an integer or a value from Nulltype Utility element to store a 2-point range of ordinal values. If one member is a null, then this is a single ended interval. Restriction of list type to store a 2-point range of ordinal values. If one member is a null, then this is a single ended interval. Utility element to store a 2-point range of numeric values. If one member is a null, then this is a single ended interval. Restriction of list type to store a 2-point range of numeric values. If one member is a null, then this is a single ended interval. Utility element to store a 2-point range of frequency values. If one member is a null, then this is a single ended interval. Restriction of list type to store a 2-point range of frequency values. If one member is a null, then this is a single ended interval. Aggregate value built using the Composite pattern. Element which refers to, or contains, a set of homogeneously typed Values. GML property which refers to, or contains, a set of homogeneously typed Values. Metadata about the rangeSet. Definition of record structure. This is required if the rangeSet is encoded in a DataBlock. We use a gml:_Value with empty values as a map of the composite value structure. List of codes that identifies the file structure model for records stored in files. A discrete coverage consists of a domain set, range set and optionally a coverage function. The domain set consists of either geometry or temporal objects, finite in number. The range set is comprised of a finite number of attribute values each of which is associated to every direct position within any single spatiotemporal object in the domain. In other words, the range values are constant on each spatiotemporal object in the domain. This coverage function maps each element from the coverage domain to an element in its range. This definition conforms to ISO 19123. The function or rule which defines the map from members of the domainSet to the range. More functions will be added to this list Description of a rule for associating members from the domainSet with members of the rangeSet. Defines how values in the domain are mapped to the range set. The start point and the sequencing rule are specified here. If absent, the implied value is "Linear". Index position of the first grid post, which shall lie somwhere in the GridEnvelope. If absent, the startPoint is equal to the value of gridEnvelope::low from the grid definition. List of codes (adopted from ISO 19123 Annex C) that identifies the rule for traversing a grid to correspond with the sequence of members of the rangeSet. The enumeration value here indicates the incrementation order to be used on the first 2 axes, i.e. "+x-y" means that the points on the first axis are to be traversed from lowest to highest and the points on the second axis are to be traversed from highest to lowest. The points on all other axes (if any) beyond the first 2 are assumed to increment from lowest to highest. XML List based on XML Schema integer type. An element of this type contains a space-separated list of integer values Should be substitutionGroup="gml:Grid" but changed in order to accomplish Xerces-J schema validation A rectified grid has an origin and vectors that define its post locations. An unrectified grid, which is a network composed of two or more sets of equally spaced parallel lines in which the members of each set intersect the members of the other sets at right angles. Provides grid coordinate values for the diametrically opposed corners of an envelope that bounds a section of grid. The value of a single coordinate is the number of offsets from the origin of the grid in the direction of a specific axis. A property that has a point as its value domain can either be an appropriate geometry element encapsulated in an of this type or an XLink reference to a remote geometry element (where remote includes geometry elements located in the same document). Either the reference or the contained element shall be given, but neither both nor none. This attribute group includes the XLink attributes (see xlinks.xsd). XLink is used in GML to reference remote (including those elsewhere in the same document). A simple link element can be constructed by including a specific of XLink attributes. The XML Linking Language (XLink) is currently a Proposed Recommendation of the World Wide Web Consortium. allows elements to be inserted into XML documents so as to create sophisticated links between resources; such links can be to reference remote properties. A simple link element can be used to implement pointer functionality, and this functionality has built into various GML 3 elements by including the gml:AssociationAttributeGroup. A Point is defined by a single coordinate tuple. GML supports two different ways to specify the direct poisiton of a point. 1. The "pos" element is of type . Deprecated with GML version 3.1.0 for coordinates with ordinate values that are numbers. Use "pos" . The "coordinates" element shall only be used for coordinates with ordinates that require a string , e.g. DMS representations. Deprecated with GML version 3.0. Use "pos" instead. The "coord" element is included for compatibility with GML 2. This is the abstract root type of the geometric primitives. A geometric primitive is a geometric object that is not further into other primitives in the system. All primitives are oriented in the direction implied by the sequence of their tuples. The "_GeometricPrimitive" element is the abstract head of the substituition group for all (pre- and user-defined) primitives. A LineString is a special curve that consists of a single segment with linear interpolation. It is defined by two or more coordinate , with linear interpolation between them. It is backwards compatible with the LineString of GML 2, GM_LineString of ISO 19107 is by LineStringSegment. GML supports two different ways to specify the control points of a line string. 1. A sequence of "pos" (DirectPositionType) or "pointProperty" (PointPropertyType) elements. "pos" elements are control points that are only part this curve, "pointProperty" elements contain a point that may be referenced from other geometry elements or reference point defined outside of this curve (reuse of existing points). 2. The "posList" element allows for a compact way to the coordinates of the control points, if all control points are in the same coordinate reference systems and belong this curve only. The number of direct positions in the list shall be at least two. Deprecated with GML version 3.1.0. Use "pointProperty" instead. Included for backwards compatibility GML 3.0.0. Deprecated with GML version 3.0. Use "pos" instead. The "coord" element is included for backwards with GML 2. Deprecated with GML version 3.1.0. Use "posList" instead. An abstraction of a curve to support the different levels of complexity. The curve can always be viewed as a geometric , i.e. is continuous. This property element either references a point via the XLink-attributes or contains the point element. pointProperty the predefined property which can be used by GML Application Schemas whenever a GML Feature has a property with a value that substitutable for Point. Deprecated with GML version 3.1.0. Use "pointProperty" instead. Included for backwards compatibility with GML 3.0.0. DirectPositionList instances hold the coordinates for a sequence of direct positions within the same coordinate system (CRS). "count" allows to specify the number of direct positions in the list. If the attribute count is present then attribute srsDimension shall be present, too. The "_Curve" element is the abstract head of the substituition group for all (continuous) curve elements. A Polygon is a special surface that is defined by a single surface patch. The boundary of this patch is coplanar and the polygon uses planar interpolation in its interior. It is backwards compatible with the Polygon of GML 2, GM_Polygon of ISO 19107 is implemented by PolygonPatch. abstraction of a surface to support the different levels of complexity. A surface is always a continuous region of a plane. A boundary of a surface consists of a number of rings. In the normal 2D case, one of these rings is distinguished as being the exterior boundary. In a general manifold this is not always possible, in which case all boundaries shall be listed as interior boundaries, and the exterior will be empty. Encapsulates a ring to represent the surface boundary property of a surface. The "_Ring" element is the abstract head of the substituition group for all closed boundaries of a surface patch. abstraction of a ring to support surface boundaries of different complexity. A boundary of a surface consists of a number of rings. The "interior" rings seperate the surface / surface patch from the area enclosed by the rings. The "_Surface" element is the abstract head of the substituition group for all (continuous) surface elements. A LinearRing is defined by four or more coordinate tuples, with linear interpolation between them; the first and last coordinates shall be coincident. GML supports two different ways to specify the control points of a linear ring. . A sequence of "pos" (DirectPositionType) or "pointProperty" (PointPropertyType) elements. "pos" elements are control points that are only part of this ring, "pointProperty" elements contain a point that may be referenced from other geometry elements or reference another point defined outside of this ring (reuse of existing points). . The "posList" element allows for a compact way to specifiy the coordinates of the control points, if all control points are in the same coordinate reference systems and belong to this ring only. The number of direct positions in the list shall be at least four. Deprecated with GML version 3.1.0. Use "pointProperty" instead. Included for backwards compatibility with GML 3.0.0. Deprecated with GML version 3.1.0. Use "posList" instead. Deprecated with GML version 3.0 and included for backwards compatibility with GML 2. Use "pos" elements instead. A non-abstract bag that is specialized for use as a dictionary which contains a set of definitions. These definitions are referenced from other places, in the same and different XML documents. In this restricted type, the inherited optional "description" element can be used for a description of this dictionary. The inherited optional "name" element can be used for the name(s) of this dictionary. The inherited "metaDataProperty" elements can be used to reference or contain more information about this dictionary. The inherited required gml:id attribute allows the dictionary to be referenced using this handle. An entry in this dictionary. The content of an entry can itself be a lower level dictionary or definition collection. This element follows the standard GML property model, so the value may be provided directly or by reference. Note that if the value is provided by reference, this definition does not carry a handle (gml:id) in this context, so does not allow external references to this specific entry in this context. When used in this way the referenced definition will usually be in a dictionary in the same XML document. An identified reference to a remote entry in this dictionary, to be used when this entry should be identified to allow external references to this specific entry. A definition, which can be included in or referenced by a dictionary. In this extended type, the inherited "description" optional element can hold the definition whenever only text is needed. The inherited "name" elements can provide one or more brief terms for which this is the definition. The inherited "metaDataProperty" elements can be used to reference or include more information about this definition. gml:id attribute is required - it shall be possible to reference this definition using this handle. An entry in a dictionary of definitions. An instance of this type contains or refers to a definition object. number of definitions contained in this dictionaryEntry is restricted to one, but a DefinitionCollection or Dictionary that contains multiple definitions can be substituted if needed. Specialized descendents of this dictionaryEntry might be restricted in an application schema to allow only including specified types of definitions as valid entries in a dictionary. This element in a dictionary entry contains the actual definition. A non-identified reference to a remote entry in this dictionary, to be used when this entry need not be identified to allow external references to this specific entry. The remote entry referenced will usually be in a dictionary in the same XML document. This element will usually be used in dictionaries that are inside of another dictionary. An entry in a dictionary of definitions that contains a GML object which references a remote definition object. This entry is expected to be convenient in allowing multiple elements in one XML document to contain short (abbreviated XPointer) references, which are resolved to an external definition provided in a Dictionary element in the same XML document. Specialized descendents of this dictionaryEntry might be restricted in an application schema to allow only including specified types of definitions as valid entries in a dictionary. A proxy entry in a dictionary of definitions. An element of this type contains a reference to a remote definition object. This entry is expected to be convenient in allowing multiple elements in one XML document to contain short (abbreviated XPointer) references, which are resolved to an external definition provided in a Dictionary element in the same XML document. A reference to a remote entry in this dictionary, used when this dictionary entry is identified to allow external references to this specific entry. The remote entry referenced can be in a dictionary in the same or different XML document. A pattern or base for derived types used to specify complex types corresponding to a UML aggregation association. An instance of this type serves as a pointer to a remote Object. Definition of a unit of measure which is a base unit from the system of units. A base unit cannot be derived by combination of other base units within this system. Sometimes known as "fundamental unit". Definition of a unit of measure (or uom). The definition includes a quantityType property, which indicates the phenomenon to which the units apply, and a catalogSymbol, which gives the short symbol used for this unit. This element is used when the relationship of this unit to other units or units systems is unknown. Informal description of the phenomenon or type of quantity that is measured or observed. For example, "length", "angle", "time", "pressure", or "temperature". When the quantity is the result of an observation or measurement, this term is known as Observable Type or Measurand. For global understanding of a unit of measure, it is often possible to reference an item in a catalog of units, using a symbol in that catalog. The "codeSpace" attribute in "CodeType" identifies a namespace for the catalog symbol value, and might reference the catalog. The "string" value in "CodeType" contains the value of a symbol that is unique within this catalog namespace. This symbol often appears explicitly in the catalog, but it could be a combination of symbols using a specified algebra of units. For example, the symbol "cm" might indicate that it is the "m" symbol combined with the "c" prefix. Definition of a unit of measure which is related to a preferred unit for this quantity type through a conversion formula. A method for deriving this unit by algebraic combination of more primitive units, may also be provided. This element is included when this unit has an accurate conversion to the preferred unit for this quantity type. Relation of a unit to the preferred unit for this quantity type, specified by an arithmetic conversion (scaling and/or offset). A preferred unit is either a base unit or a derived unit selected for all units of one quantity type. The mandatory attribute "uom" shall reference the preferred unit that this conversion applies to. The conversion is specified by one of two alternative elements: "factor" or "formula". Specification of the scale factor by which a value using this unit of measure can be multiplied to obtain the corresponding value using the preferred unit of measure. Specification of the formula by which a value using this unit of measure can be converted to obtain the corresponding value using the preferred unit of measure. Reference to a unit of measure definition that applies to all the numerical values described by the element containing this element. Notice that a complexType which needs to include the uom attribute can do so by extending this complexType. Alternately, this complexType can be used as a pattern for a new complexType. Reference to a unit of measure definition, usually within the same XML document but possibly outside the XML document which contains this reference. For a reference within the same XML document, the "#" symbol should be used, followed by a text abbreviation of the unit name. However, the "#" symbol may be optional, and still may be interpreted as a reference. Paremeters of a simple formula by which a value using this unit of measure can be converted to the corresponding value using the preferred unit of measure. The formula element contains elements a, b, c and d, whose values use the XML Schema type "double". These values are used in the formula y = (a + bx) / (c + dx), where x is a value using this unit, and y is the corresponding value using the preferred unit. The elements a and d are optional, and if values are not provided, those parameters are considered to be zero. If values are not provided for both a and d, the formula is equivalent to a fraction with numerator and denominator parameters. This element is included when the correct definition of this unit is unknown, but this unit has a rough or inaccurate conversion to the preferred unit for this quantity type. Definition of one unit term for a derived unit of measure. This unit term references another unit of measure (uom) and provides an integer exponent applied to that unit in defining the compound unit. The exponent can be positive or negative, but not zero. Definition of a unit of measure which is defined through algebraic combination of more primitive units, which are usually base units from a particular system of units. Derived units based directly on base units are usually preferred for quantities other than the base units or fundamental quantities within a system. If a derived unit is not the preferred unit, the ConventionalUnit element should be used instead. A 2D coordinate reference system used to approximate the shape of the earth on a planar surface, but in such a way that the distortion that is inherent to the approximation is carefully controlled and known. Distortion correction is commonly applied to calculated bearings and distances to produce values that are a close match to actual field values. A coordinate reference system that is defined by its coordinate conversion from another coordinate reference system (not by a datum). This abstract complexType shall not be used, extended, or restricted, in an Application Schema, to define a concrete subtype with a meaning equivalent to a concrete subtype specified in this document. Description of a spatial and/or temporal reference system used by a dataset. Set of alterative identifications of this reference system. The first srsID, if any, is normally the primary identification code, and any others are aliases. Comments on or information about this reference system, including source information. Basic encoding for reference system objects, simplifying and restricting the DefinitionType as needed. The name by which this reference system is identified. An identification of a reference system. An identification of a CRS object. The first use of the IdentifierType for an object, if any, is normally the primary identification code, and any others are aliases. The code or name for this Identifier, often from a controlled list or pattern defined by a code space. The optional codeSpace attribute is normally included to identify or reference a code space within which one or more codes are defined. This code space is often defined by some authority organization, where one organization may define multiple code spaces. The range and format of each Code Space identifier is defined by that code space authority. Information about that code space authority can be included as metaDataProperty elements which are optionally allowed in all CRS objects. Remarks about this code or alias. Identifier of the version of the associated codeSpace or code, as specified by the codeSpace or code authority. This version is included only when the "code" or "codeSpace" uses versions. When appropriate, the version is identified by the effective date, coded using ISO 8601 date format. Information about this object or code. Contains text or refers to external text. Area or region in which this CRS object is valid. Information about the spatial, vertical, and/or temporal extent of a reference system object. Constraints: At least one of the elements "description", "boundingBox", "boundingPolygon", "verticalExtent", and temporalExtent" shall be included, but more that one can be included when appropriate. Furthermore, more than one "boundingBox", "boundingPolygon", "verticalExtent", and/or temporalExtent" element can be included, with more than one meaning the union of the individual domains. Description of spatial and/or temporal extent of this object. Geographic domain of this reference system object. Unordered list of bounding boxes (or envelopes) whose union describes the spatial domain of this object. Unordered list of bounding polygons whose union describes the spatial domain of this object. Unordered list of vertical intervals whose union describes the spatial domain of this object. Unordered list of time periods whose union describes the spatial domain of this object. A bounding box (or envelope) defining the spatial domain of this object. A bounding polygon defining the horizontal spatial domain of this object. An interval defining the vertical spatial domain of this object. A time period defining the temporal domain of this object. The abstract supertype for temporal geometric primitives. A temporal geometry shall be associated with a temporal reference system via URI. The Gregorian calendar with UTC is the default reference system, following ISO 8601. Other reference systems in common use include the GPS calendar and the Julian calendar. The abstract supertype for temporal primitives. This abstract element acts as the head of the substitution group for temporal primitives. Direct representation of a temporal position. Indeterminate time values are also allowed, as described in ISO 19108. The indeterminatePosition attribute can be used alone or it can qualify a specific value for temporal position (e.g. before 2002-12, after 1019624400). For time values that identify position within a calendar, the calendarEraName attribute provides the name of the calendar era to which the date is referenced (e.g. the Meiji era of the Japanese calendar). The ISO 19108:2002 hierarchy of subtypes for temporal position are collapsed by defining a union of XML Schema simple types for indicating temporal position relative to a specific reference system. Dates and dateTime may be indicated with varying degrees of precision. dateTime by itself does not allow right-truncation, except for fractions of seconds. When used with non-Gregorian calendars based on years, months, days, the same lexical representation should still be used, with leading zeros added if the year value would otherwise have fewer than four digits. An ordinal position may be referenced via URI identifying the definition of an ordinal era. A time coordinate value is indicated as a decimal (e.g. UNIX time, GPS calendar). Calendar dates may be indicated with varying degrees of precision, using year, year-month, date. When used with non-Gregorian calendars based on years, months, days, the same lexical representation should still be used, with leading zeros added if the year value would otherwise have fewer than four digits. time is used for a position that recurs daily (see clause 5.4.4.2 of ISO 19108:2002). This enumerated data type specifies values for indeterminate positions. Omit back-pointers begunBy, endedBy. Direct representation of a temporal position This abstract element acts as the head of the substitution group for temporal geometric primitives. This model group is provided as an alternative to the abstract susbstitutionGroup head _timeLength. 19136 comment 411 This element is an instance of the primitive xsd:duration simple type to enable use of the ISO 8601 syntax for temporal length (e.g. P5DT4H30M). It is a valid subtype of TimeDurationType according to section 3.14.6, rule 2.2.4 in XML Schema, Part 1. element is a valid subtype of TimeDurationType to section 3.14.6, rule 2.2.4 in XML Schema, Part 1. This type extends the built-in xsd:decimal simple type to allow floating-point values for temporal length. According to the ISO 11404 model you have to use positiveInteger together with appropriate values for radix and factor. The resolution of the time interval is to one radix ^(-factor) of the specified time unit (e.g. unit="second", radix="10", factor="3" specifies a resolution of milliseconds). It is a subtype of TimeDurationType. Standard units for measuring time intervals (see ISO 31-1). Description of domain of usage, or limitations of usage, for which this CRS object is valid. Association to the coordinate reference system used by this derived CRS. Association to a coordinate reference system, either referencing or containing the definition of that reference system. A coordinate reference system consists of an ordered sequence of coordinate system axes that are related to the earth through a datum. A coordinate reference system is defined by one datum and by one coordinate system. Most coordinate reference system do not move relative to the earth, except for engineering coordinate reference systems defined on moving platforms such as cars, ships, aircraft, and spacecraft. For further information, see OGC Abstract Specification Topic 2. reference systems are commonly divided into sub-types. The common classification criterion for sub-typing of coordinate reference systems is the way in which they deal with earth curvature. This has a direct effect on the portion of the earth's surface that can be covered by that type of CRS with an acceptable degree of error. The exception to the rule is the subtype "Temporal" which has been added by analogy. Abstract coordinate reference system, usually defined by a coordinate system and a datum. This abstract complexType shall not be used, extended, or restricted, in an Application Schema, to define a concrete subtype with a meaning equivalent to a concrete subtype specified in this document. Association to the coordinate conversion used to define this derived CRS. Association to a general conversion, either referencing or containing the definition of that conversion. An abstract operation on coordinates that does not include any change of datum. The best-known example of a coordinate conversion is a map projection. The parameters describing coordinate conversions are defined rather than empirically derived. Note that some conversions have no parameters. abstract complexType is expected to be extended for well-known operation methods with many Conversion instances, in Application Schemas that define operation-method-specialized element names and contents. This conversion uses an operation method, usually with associated parameter values. However, operation methods and parameter values are directly associated with concrete subtypes, not with this abstract type. All concrete types derived from this type shall extend this type to include a "usesMethod" element that references the "OperationMethod" element. Similarly, all concrete types derived from this type shall extend this type to include zero or more elements each named "uses...Value" that each use the type of an element substitutable for the "_generalParameterValue" element. A mathematical operation on coordinates that transforms or converts coordinates to another coordinate reference system. Many but not all coordinate operations (from CRS A to CRS B) also uniquely define the inverse operation (from CRS B to CRS A). In some cases, the operation method algorithm for the inverse operation is the same as for the forward algorithm, but the signs of some operation parameter values shall be reversed. In other cases, different algorithms are required for the forward and inverse operations, but the same operation parameter values are used. If (some) entirely different parameter values are needed, a different coordinate operation shall be defined. Set of alternative identifications of this coordinate operation. The first coordinateOperationID, if any, is normally the primary identification code, and any others are aliases. Comments on or information about this coordinate operation, including source information. Unordered set of estimates of the impact of this coordinate operation on point position accuracy. Gives position error estimates for target coordinates of this coordinate operation, assuming no errors in source coordinates. Basic encoding for coordinate operation objects, simplifying and restricting the DefinitionType as needed. The name by which this coordinate operation is identified. An identification of a coordinate operation. Version of the coordinate transformation (i.e., instantiation due to the stochastic nature of the parameters). Mandatory when describing a transformation, and should not be supplied for a conversion. Position error estimate (or accuracy) data. A description of the position accuracy parameter(s) provided. Association to the source CRS (coordinate reference system) of this coordinate operation. Association to a CRS abstract coordinate reference system, either referencing or containing the definition of that CRS. Association to the target CRS (coordinate reference system) of this coordinate operation. For constraints on multiplicity of "sourceCRS" and "targetCRS", see UML model of Coordinate Operation package in OGC Abstract Specification topic 2. A parameterized mathematical operation on coordinates that transforms or converts coordinates to another coordinate reference system. This coordinate operation uses an operation method, usually with associated parameter values. However, operation methods and parameter values are directly associated with concrete subtypes, not with this abstract type. abstract complexType shall not be directly used, extended, or restricted in a compliant Application Schema. A single (not concatenated) coordinate operation. Association to the Cartesian coordinate system used by this CRS. Association to a Cartesian coordinate system, either referencing or containing the definition of that coordinate system. A 1-, 2-, or 3-dimensional coordinate system. Gives the position of points relative to orthogonal straight axes in the 2- and 3-dimensional cases. In the 1-dimensional case, it contains a single straight coordinate axis. In the multi-dimensional case, all axes shall have the same length unit of measure. A CartesianCS shall have one, two, or three usesAxis associations. A coordinate system (CS) is the set of coordinate system axes that spans a given coordinate space. A CS is derived from a set of (mathematical) rules for specifying how coordinates in a given space are to be assigned to points. The coordinate values in a coordinate tuple shall be recorded in the order in which the coordinate system axes associations are recorded, whenever those coordinates use a coordinate reference system that uses this coordinate system. This abstract complexType shall not be used, extended, or restricted, in an Application Schema, to define a concrete subtype with a meaning equivalent to a concrete subtype specified in this document. Set of alternative identifications of this coordinate system. The first csID, if any, is normally the primary identification code, and any others are aliases. Comments on or information about this coordinate system, including data source information. Ordered sequence of associations to the coordinate system axes included in this coordinate system. Basic encoding for coordinate system objects, simplifying and restricting the DefinitionType as needed. The name by which this coordinate system is identified. An identification of a coordinate system. Association to a coordinate system axis. Association to a coordinate system axis, either referencing or containing the definition of that axis. Definition of a coordinate system axis. Set of alternative identifications of this coordinate system axis. The first axisID, if any, is normally the primary identification code, and any others are aliases. Comments on or information about this coordinate system axis, including data source information. Basic encoding for coordinate system axis objects, simplifying and restricting the DefinitionType as needed. The name by which this coordinate system axis is identified. An identification of a coordinate system axis. The abbreviation used for this coordinate system axis. This abbreviation can be used to identify the ordinates in a coordinate tuple. Examples are X and Y. The codeSpace attribute can reference a source of more information on a set of standardized abbreviations, or on this abbreviation. Direction of this coordinate system axis (or in the case of Cartesian projected coordinates, the direction of this coordinate system axis at the origin). Examples: north or south, east or west, up or down. Within any set of coordinate system axes, only one of each pair of terms can be used. For earth-fixed CRSs, this direction is often approximate and intended to provide a human interpretable meaning to the axis. When a geodetic datum is used, the precise directions of the axes may therefore vary slightly from this approximate direction. Note that an EngineeringCRS can include specific descriptions of the directions of its coordinate system axes. For example, the path of a linear CRS axis can be referenced in another document, such as referencing a GML feature that references or includes a curve geometry. The codeSpace attribute can reference a source of more information on a set of standardized directions, or on this direction. Identifier of the unit of measure used for this coordinate system axis. The value of this coordinate in a coordinate tuple shall be recorded using this unit of measure, whenever those coordinates use a coordinate reference system that uses a coordinate system that uses this axis. A concrete operation on coordinates that does not include any change of Datum. The best-known example of a coordinate conversion is a map projection. The parameters describing coordinate conversions are defined rather than empirically derived. Note that some conversions have no parameters. concrete complexType can be used with all operation methods, without using an Application Schema that defines operation-method-specialized element names and contents, especially for methods with only one Conversion instance. Unordered list of composition associations to the set of parameter values used by this conversion operation. Association to the operation method used by this coordinate operation. Association to a concrete general-purpose operation method, either referencing or containing the definition of that method. Definition of an algorithm used to perform a coordinate operation. Most operation methods use a number of operation parameters, although some coordinate conversions use none. Each coordinate operation using the method assigns values to these parameters. Set of alternative identifications of this operation method. The first methodID, if any, is normally the primary identification code, and any others are aliases. Comments on or information about this operation method, including source information. Unordered list of associations to the set of operation parameters and parameter groups used by this operation method. Basic encoding for operation method objects, simplifying and restricting the DefinitionType as needed. The name by which this operation method is identified. An identification of an operation method. Formula(s) used by this operation method. The value may be a reference to a publication. Note that the operation method may not be analytic, in which case this element references or contains the procedure, not an analytic formula. Number of dimensions in the source CRS of this operation method. Number of dimensions in the target CRS of this operation method. Association to an operation parameter or parameter group used by this operation method. Association to an operation parameter or group, either referencing or containing the definition of that parameter or group. Abstract definition of a parameter or group of parameters used by an operation method. The minimum number of times that values for this parameter group or parameter are required. If this attribute is omitted, the minimum number is one. Composition association to a parameter value used by this coordinate operation. A parameter value, ordered sequence of values, or reference to a file of parameter values. This concrete complexType can be used for operation methods without using an Application Schema that defines operation-method-specialized element names and contents, especially for methods with only one instance. This complexType can be used, extended, or restricted for well-known operation methods, especially for methods with many instances. Abstract parameter value or group of parameter values. abstract complexType is expected to be extended and restricted for well-known operation methods with many instances, in Application Schemas that define operation-method-specialized element names and contents. Specific parameter value elements are directly contained in concrete subtypes, not in this abstract type. All concrete types derived from this type shall extend this type to include one "...Value" element with an appropriate type, which should be one of the element types allowed in the ParameterValueType. In addition, all derived concrete types shall extend this type to include a "valueOfParameter" element that references one element substitutable for the "OperationParameter" element. Numeric value of an operation parameter, with its associated unit of measure. Value of an angle operation parameter, in either degree-minute-second format or single value format. Angle value provided in degree-minute-second or degree-minute format. Integer number of degrees, plus the angle direction. This element can be used for geographic Latitude and Longitude. For Latitude, the XML attribute direction can take the values "N" or "S", meaning North or South of the equator. For Longitude, direction can take the values "E" or "W", meaning East or West of the prime meridian. This element can also be used for other angles. In that case, the direction can take the values "+" or "-" (of SignType), in the specified rotational direction from a specified reference direction. Integer number of degrees in a degree-minute-second or degree-minute angular value, without indication of direction. Utility type used in various places - e.g. to indicate the direction of topological objects; "+" for forwards, or "-" for backwards. Decimal number of arc-minutes in a degree-minute angular value. Integer number of arc-minutes in a degree-minute-second angular value. Number of arc-seconds in a degree-minute-second angular value. String value of an operation parameter. A string value does not have an associated unit of measure. Positive integer value of an operation parameter, usually used for a count. An integer value does not have an associated unit of measure. Boolean value of an operation parameter. A Boolean value does not have an associated unit of measure. Ordered sequence of two or more numeric values of an operation parameter list, where each value has the same associated unit of measure. An element of this type contains a space-separated sequence of double values. List of numbers with a uniform scale. The value of uom (Units Of Measure) attribute is a reference to a Reference System for the amount, either a ratio or position scale. Ordered sequence of two or more integer values of an operation parameter list, usually used for counts. These integer values do not have an associated unit of measure. An element of this type contains a space-separated sequence of integer values. Reference to a file or a part of a file containing one or more parameter values, each numeric value with its associated unit of measure. When referencing a part of a file, that file shall contain multiple identified parts, such as an XML encoded document. Furthermore, the referenced file or part of a file can reference another part of the same or different files, as allowed in XML documents. Association to the operation parameter that this is a value of. Association to an operation parameter, either referencing or containing the definition of that parameter. The definition of a parameter used by an operation method. Most parameter values are numeric, but other types of parameter values are possible. This complexType is expected to be used or extended for all operation methods, without defining operation-method-specialized element names. Set of alternative identifications of this operation parameter. The first parameterID, if any, is normally the primary identification code, and any others are aliases. Comments on or information about this operation parameter, including source information. Basic encoding for operation parameter objects, simplifying and restricting the DefinitionType as needed. The name by which this operation parameter is identified. An identification of an operation parameter. A coordinate reference system based on an ellipsoidal approximation of the geoid; this provides an accurate representation of the geometry of geographic features for a large portion of the earth's surface. Association to the ellipsoidal coordinate system used by this CRS. Association to an ellipsoidal coordinate system, either referencing or containing the definition of that coordinate system. A two- or three-dimensional coordinate system in which position is specified by geodetic latitude, geodetic longitude, and (in the three-dimensional case) ellipsoidal height. An EllipsoidalCS shall have two or three usesAxis associations. Association to the geodetic datum used by this CRS. Association to a geodetic datum, either referencing or containing the definition of that datum. A geodetic datum defines the precise location and orientation in 3-dimensional space of a defined ellipsoid (or sphere) that approximates the shape of the earth, or of a Cartesian coordinate system centered in this ellipsoid (or sphere). A datum specifies the relationship of a coordinate system to the earth, thus creating a coordinate reference system. A datum uses a parameter or set of parameters that determine the location of the origin of the coordinate reference system. Each datum subtype can be associated with only specific types of coordinate systems. This abstract complexType shall not be used, extended, or restricted, in an Application Schema, to define a concrete subtype with a meaning equivalent to a concrete subtype specified in this document. Set of alternative identifications of this datum. The first datumID, if any, is normally the primary identification code, and any others are aliases. Comments on this reference system, including source information. Basic encoding for datum objects, simplifying and restricting the DefinitionType as needed. The name by which this datum is identified. An identification of a datum. Description, possibly including coordinates, of the point or points used to anchor the datum to the Earth. Also known as the "origin", especially for engineering and image datums. The codeSpace attribute can be used to reference a source of more detailed on this point or surface, or on a set of such descriptions. For a geodetic datum, this point is also known as the fundamental point, which is traditionally the point where the relationship between geoid and ellipsoid is defined. In some cases, the "fundamental point" may consist of a number of points. In those cases, the parameters defining the geoid/ellipsoid relationship have been averaged for these points, and the averages adopted as the datum definition. For an engineering datum, the anchor point may be a physical point, or it may be a point with defined coordinates in another CRS. When appropriate, the coordinates of this anchor point can be referenced in another document, such as referencing a GML feature that references or includes a point position. For an image datum, the anchor point is usually either the centre of the image or the corner of the image. For a temporal datum, this attribute is not defined. Instead of the anchor point, a temporal datum carries a separate time origin of type DateTime. The time after which this datum definition is valid. This time may be precise (e.g. 1997.0 for IRTF97) or merely a year (e.g. 1983 for NAD83). In the latter case, the epoch usually refers to the year in which a major recalculation of the geodetic control network, underlying the datum, was executed or initiated. An old datum can remain valid after a new datum is defined. Alternatively, a datum may be superseded by a later datum, in which case the realization epoch for the new datum defines the upper limit for the validity of the superseded datum. Association to the prime meridian used by this geodetic datum. Association to a prime meridian, either referencing or containing the definition of that meridian. A prime meridian defines the origin from which longitude values are determined. Set of alternative identifications of this prime meridian. The first meridianID, if any, is normally the primary identification code, and any others are aliases. Comments on or information about this prime meridian, including source information. Basic encoding for prime meridian objects, simplifying and restricting the DefinitionType as needed. The name by which this prime meridian is identified. The meridianName most common value is Greenwich, and that value shall be used when the greenwichLongitude value is zero. An identification of a prime meridian. Longitude of the prime meridian measured from the Greenwich meridian, positive eastward. The greenwichLongitude most common value is zero, and that value shall be used when the meridianName value is Greenwich. Value of an angle quantity provided in either degree-minute-second format or single value format. Value of an angle quantity recorded as a single number, with its units. Uses the MeasureType with the restriction that the unit of measure referenced by uom shall be suitable for an angle, such as degrees or radians. Association to the ellipsoid used by this geodetic datum. Association to an ellipsoid, either referencing or containing the definition of that ellipsoid. An ellipsoid is a geometric figure that can be used to describe the approximate shape of the earth. In mathematical terms, it is a surface formed by the rotation of an ellipse about its minor axis. Set of alternative identifications of this ellipsoid. The first ellipsoidID, if any, is normally the primary identification code, and any others are aliases. Comments on or information about this ellipsoid, including source information. Basic encoding for ellipsoid objects, simplifying and restricting the DefinitionType as needed. The name by which this ellipsoid is identified. An identification of an ellipsoid. Length of the semi-major axis of the ellipsoid. Value of a length (or distance) quantity, with its units. Uses the MeasureType with the restriction that the unit of measure referenced by uom shall be suitable for a length, such as metres or feet. Definition of the second parameter that defines the shape of an ellipsoid. An ellipsoid requires two defining parameters: semi-major axis and inverse flattening or semi-major axis and semi-minor axis. When the reference body is a sphere rather than an ellipsoid, only a single defining parameter is required, namely the radius of the sphere; in that case, the semi-major axis "degenerates" into the radius of the sphere. Inverse flattening value of the ellipsoid. Value of a scale factor (or ratio) that has no physical unit. Uses the MeasureType with the restriction that the unit of measure referenced by uom shall be suitable for a scale factor, such as percent, permil, or parts-per-million. Length of the semi-minor axis of the ellipsoid. The ellipsoid is degenerate and is actually a sphere. The sphere is completely defined by the semi-major axis, which is the radius of the sphere. A property that has a curve as its value domain can either be an appropriate geometry element encapsulated in an of this type or an XLink reference to a remote geometry element (where remote includes geometry elements located elsewhere the same document). Either the reference or the contained element shall be given, but neither both nor none. This attribute group includes the XLink attributes (see xlinks.xsd). XLink is used in GML to reference remote (including those elsewhere in the same document). A simple link element can be constructed by including a specific of XLink attributes. The XML Linking Language (XLink) is currently a Proposed Recommendation of the World Wide Web Consortium. allows elements to be inserted into XML documents so as to create sophisticated links between resources; such links can be used reference remote properties. A simple link element can be used to implement pointer functionality, and this functionality has been built various GML 3 elements by including the gml:AssociationAttributeGroup. A property that has a surface as its value domain can either be an appropriate geometry element encapsulated in an element of this type or an XLink reference to a remote geometry element (where remote includes geometry elements located elsewhere in the same document). Either the reference or the contained element shall be given, but neither both nor none. This attribute group includes the XLink attributes (see xlinks.xsd). XLink is used in GML to reference remote resources (including those elsewhere in the same document). A simple link element can be constructed by including a specific set of XLink attributes. The XML Linking Language (XLink) is currently a Proposed Recommendation of the World Wide Web Consortium. XLink allows elements to be inserted into XML documents so as to create sophisticated links between resources; such links can be used to reference remote properties.simple link element can be used to implement pointer functionality, and this functionality has been built into various GML 3 elements by including the gml:AssociationAttributeGroup. A geometric property can either be any geometry element encapsulated in an element of this type or an XLink reference a remote geometry element (where remote includes geometry elements located elsewhere in the same document). Note that either reference or the contained element shall be given, but not both or none. This attribute group includes the XLink attributes (see xlinks.xsd). XLink is used in GML to reference resources (including those elsewhere in the same document). A simple link element can be constructed by a specific set of XLink attributes. The XML Linking Language (XLink) is currently a Proposed Recommendation the World Wide Web Consortium. XLink allows elements to be inserted into XML documents so as to create links between resources; such links can be used to reference remote properties. A simple link element be used to implement pointer functionality, and this functionality has been built into various GML 3 elements by the gml:AssociationAttributeGroup. This type is deprecated with GML 3 and shall not be used. It is included for backwards compatibility with GML 2. Use SurfacePropertyType instead.property that has a polygon as its value domain can either be an appropriate geometry element encapsulated in an element of this type or an XLink reference to a remote geometry element (where remote includes geometry elements located elsewhere in the same document). Either the reference or the contained element shall be given, but neither both nor none. This attribute group includes the XLink attributes (see xlinks.xsd). XLink is used in GML to reference remote resources (including those elsewhere in the same document). A simple link element can be constructed by including a specific set of XLink attributes. The XML Linking Language (XLink) is currently a Proposed Recommendation of the World Wide Web Consortium. XLink allows elements to be inserted into XML documents so as to create sophisticated links between resources; such links can be used to reference remote properties.simple link element can be used to implement pointer functionality, and this functionality has been built into various GML 3 elements by including the gml:AssociationAttributeGroup. Top-level property. Used in application schemas to "attach" the styling information to GML data. The link between the data and the style should be established through this property only. [complexType of] Top-level property. Used in application schemas to "attach" the styling information to GML data. The link between the data and the style should be established through this property only. The value of the top-level property. It is an abstract element. Used as the head element of the substitution group for extensibility purposes. [complexType of] The value of the top-level property. It is an abstract element. Used as the head element of the substitution group for extensibility purposes. MultiSurface is defined by one or more Surfaces, referenced through surfaceMember elements. The members of the geometric aggregate can be specified either using the "standard" property or the array property style. It is also valid to use both the "standard" and the array property style in the same collection.: Array properties cannot reference remote geometry elements. This is the abstract root type of the geometric aggregates. This property element either references a surface via the XLink-attributes or contains the surface element. A surface element is any element which is substitutable for "_Surface". This property element contains a list of surfaces. The order of the elements is significant and shall be preserved when processing the array. A container for an array of surfaces. The elements are always contained in the array property, referencing geometry elements or arrays of geometry elements is not supported. The "_GeometricAggregate" element is the abstract head of the substituition group for all geometric aggremates. Predefined concrete value of the top-level property. Encapsulates all other styling information. [complexType of] Predefined concrete value of the top-level property. Encapsulates all other styling information. The style descriptor for features. [complexType of] The style descriptor for features. The style descriptor for geometries of a feature. [complexType of] The style descriptor for geometries of a feature. deprecated Deprecated in GML version 3.1.0. Use symbol with inline content instead. Base complex type for geometry, topology, label and graph styles. Used to vary individual graphic parameters and attributes of the style, symbol or text. The symbol property. Extends the gml:AssociationType to allow for remote referencing of symbols. [complexType of] The symbol property. Allows for remote referencing of symbols. Used to specify the type of the symbol used. Defines the geometric transformation of entities. There is no particular grammar defined for this value. The style descriptor for labels of a feature, geometry or topology. [complexType of] The style descriptor for labels of a feature, geometry or topology. Label is mixed -- composed of text and XPath expressions used to extract the useful information from the feature. The style descriptor for topologies of a feature. Describes individual topology elements styles. [complexType of] The style descriptor for topologies of a feature. Describes individual topology elements styles. deprecated Deprecated in GML version 3.1.0. Use symbol with inline content instead. Used to specify the grammar of the feature query mechanism. The style descriptor for a graph consisting of a number of features. Describes graph-specific style attributes. [complexType of] The style descriptor for a graph consisting of a number of features. Describes graph-specific style attributes. Graph-specific styling property. Graph-specific styling property. Graph-specific styling property. Graph-specific styling property. Abstract element which acts as the head of a substitution group for packages of MetaData properties. An abstract base type for complex metadata types.