4.6 Geography Markup Language (GML) (ISO 19136)
183
3. Names for directions
4. Definitions and dictionaries
4.6.2 GML application schema
A GML application schema is an XML Schema, conforming to the rules outlined
in the ISO 19136 document. The application schema is a combination of a GML profile and application-specific definitions. It describes one or more types of geographie objects, components of geographie objects, or meta data, including dictionaries and definitions, used in the definition of geographie objects.
The definition of a GML application schema must follow a number of rules. They
shall guarantee the readability of and the ability to process a GML document by any
GML parser and shall allow for the worldwide transport and storage of GML datasets without interference with other GML datasets.
The rules have mostly three components:
1. The application schema must declare a target namespace. This is the namespace
in which the terms like the application specific feature types and coverage "live".
This must not be the GML namespace. The GML namespace is defined in about
20 XML schemas such as geometryPrimitives.xsd and coverage.xsd.
2. All geographie features in the application schema must be declared as global elements in the schema. The content model for such global elements must derive either directly or indirectly from gml:AbstractFeatureType.
3. Elements representing properties of features may be declared as global elements
in an application schema, or they may be declared locally within feature content
models (type definitions). The type for a property element may be derived from
gm1:AssociationType or gml:ArrayAssociationType, or may follow the pattern of
gml:AssociationType.
4.6.3 Relation between GML, OGC, and the ISO 19100 standards
GML is being developed by the GML Revision Working Group ofthe Open GIS
Consortium (OGC). GML is related to the OGC Abstract Specification and published as one of their Implementation Specifications.
ISO has adopted GML as the ISO 19136 (Geography Markup Language) standard. The standardisation process is ongoing.
Relation to ISO 19107 (Spatial schema)
The implementation standard ISO 19136 conforms to the other standards of the
ISO 19100 family. The closest relation exists to the ISO 19107.
183
3. Names for directions
4. Definitions and dictionaries
4.6.2 GML application schema
A GML application schema is an XML Schema, conforming to the rules outlined
in the ISO 19136 document. The application schema is a combination of a GML profile and application-specific definitions. It describes one or more types of geographie objects, components of geographie objects, or meta data, including dictionaries and definitions, used in the definition of geographie objects.
The definition of a GML application schema must follow a number of rules. They
shall guarantee the readability of and the ability to process a GML document by any
GML parser and shall allow for the worldwide transport and storage of GML datasets without interference with other GML datasets.
The rules have mostly three components:
1. The application schema must declare a target namespace. This is the namespace
in which the terms like the application specific feature types and coverage "live".
This must not be the GML namespace. The GML namespace is defined in about
20 XML schemas such as geometryPrimitives.xsd and coverage.xsd.
2. All geographie features in the application schema must be declared as global elements in the schema. The content model for such global elements must derive either directly or indirectly from gml:AbstractFeatureType.
3. Elements representing properties of features may be declared as global elements
in an application schema, or they may be declared locally within feature content
models (type definitions). The type for a property element may be derived from
gm1:AssociationType or gml:ArrayAssociationType, or may follow the pattern of
gml:AssociationType.
4.6.3 Relation between GML, OGC, and the ISO 19100 standards
GML is being developed by the GML Revision Working Group ofthe Open GIS
Consortium (OGC). GML is related to the OGC Abstract Specification and published as one of their Implementation Specifications.
ISO has adopted GML as the ISO 19136 (Geography Markup Language) standard. The standardisation process is ongoing.
Relation to ISO 19107 (Spatial schema)
The implementation standard ISO 19136 conforms to the other standards of the
ISO 19100 family. The closest relation exists to the ISO 19107.