gml:Dictionary 

Sets of definitions may be collected into dictionaries or collections.
A gml:Dictionary is a non-abstract collection of definitions.
The gml:Dictionary content model adds a list of gml:dictionaryEntry properties that contain or reference gml:Definition objects.  A database handle (gml:id attribute) is required, in order that this collection may be referred to. The standard gml:identifier, gml:description, gml:descriptionReference and gml:name properties are available to reference or contain more information about this dictionary. The gml:description and gml:descriptionReference property elements may be used for a description of this dictionary. The derived gml:name element may be used for the name(s) of this dictionary. for remote definiton references gml:dictionaryEntry shall be used. If a Definition object contained within a Dictionary uses the descriptionReference property to refer to a remote definition, then this enables the inclusion of a remote definition in a local dictionary, giving a handle and identifier in the context of the local dictionary.

Element Information

Model

gml:metaDataProperty* , gml:description{0,1} , gml:descriptionReference{0,1} , gml:identifier , gml:name* , gml:remarks{0,1} , (gml:dictionaryEntry | gml:indirectEntry)
Children: gml:description, gml:descriptionReference, gml:dictionaryEntry, gml:identifier, gml:indirectEntry, gml:metaDataProperty, gml:name, gml:remarks

Attributes

QName Type Fixed Default Use Inheritable Annotation
aggregationType gml:AggregationType optional
gml:id ID required 
The attribute gml:id supports provision of a handle for the XML element representing a GML Object. Its use is mandatory for all GML objects. It is of XML type ID, so is constrained to be unique in the XML document within which it occurs.

Source 

<element name="Dictionary" type="gml:DictionaryType" substitutionGroup="gml:Definition">
  <annotation>
    <documentation>Sets of definitions may be collected into dictionaries or collections. A gml:Dictionary is a non-abstract collection of definitions. The gml:Dictionary content model adds a list of gml:dictionaryEntry properties that contain or reference gml:Definition objects. A database handle (gml:id attribute) is required, in order that this collection may be referred to. The standard gml:identifier, gml:description, gml:descriptionReference and gml:name properties are available to reference or contain more information about this dictionary. The gml:description and gml:descriptionReference property elements may be used for a description of this dictionary. The derived gml:name element may be used for the name(s) of this dictionary. for remote definiton references gml:dictionaryEntry shall be used. If a Definition object contained within a Dictionary uses the descriptionReference property to refer to a remote definition, then this enables the inclusion of a remote definition in a local dictionary, giving a handle and identifier in the context of the local dictionary.</documentation>
  </annotation>
</element>

Sample