Introduction Import GML observation schema components

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21.9.4 Observation collections

All observation collections in the GML application schema shall be declared as global elements in the schema, i.e. they shall be child elements of the XML Schema schema element. An observation collection shall be a feature collection as described in 9.9 whose members are observations.

21.9.5 Observations are features

An observation defined in an application schema shall conform to the rules respecting GML features as described in Clause 9 and Clause 7. See also 21.3.4.

21.9.6 Observation collection document

Following the rules for GML documents see 21.1, an Observation Collection document may reference observations that are defined in any number of GML application schemas and these may define observations only, observation collections or any combination of the same.

21.10 Schemas defining dictionaries and definitions

21.10.1 Introduction

The following subclauses describe how to create an application schema for definitions. Definitions and dictionaries are described in Clause 15. One set of specialized definitions is built in to GML, for units of measure, and serves as an example of how to derive specialized definition components. An application schema for definitions defines one or more types of definition in accordance with the following rules.

21.10.2 Import GML dictionary schema components

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

21.10.3 User-defined definition types

All definitions in the application schema shall be declared as global elements in the schema, i.e. they shall be immediate child elements of the XML Schema schema element. The content model for such global elements shall derive either directly or indirectly from gml:DefinitionType. Authors of application schemas may create their own definition types if GML lacks the desired construct. To do this, authors shall ensure that the object elements of these definition types are in the substitution group either directly or indirectly of the corresponding GML object element: gml:Definition. All rules specified in Clauses 7 and 15 shall be followed.

21.10.4 User-defined dictionary types

A dictionary in the application schema shall be declared as a global element in the schema, that is it shall be a child element of the XML Schema schema element. The content model for such global elements shall derive either directly or indirectly from gml:DictionaryType.