4 Copyright © 2012 Open Geospatial Consortium.
SIG 3D Special Interest Group 3D of the GDI-DE
TC211 ISO Technical Committee 211
TIC Terrain Intersection Curve
TIN Triangulated Irregular Network
UML Unified Modeling Language
URI Uniform Resource Identifier
VRML Virtual Reality Modeling Language
W3C World Wide Web Consortium
W3DS OGC Web 3D Service
WFS OGC Web Feature Service
X3D Open Standards XML-enabled 3D file format of the Web 3D Consortium
XML Extensible Markup Language
xAL OASIS extensible Address Language
4.2 UML Notation
The CityGML standard is presented in this document in diagrams using the Unified Modeling Language UML static structure diagram see Booch et al. 1997. The UML notations used in this standard are described in the
diagram below Fig. 1.
Fig. 1: UML notation see ISO TS 19103, Geographic information - Conceptual schema language.
According to GML3 all associations between model elements in CityGML are uni-directional. Thus, associa- tions in CityGML are navigable in only one direction. The direction of navigation is depicted by an arrowhead.
In general, the context an element takes within the association is indicated by its role. The role is displayed near the target of the association. If the graphical representation is ambiguous though, the position of the role has to
be drawn to the element the association points to.
Copyright © 2012 Open Geospatial Consortium. 5
The following stereotypes are used: Geometry represents the geometry of an object. The geometry is an identifiable and distinguishable object
that is derived from the abstract GML type AbstractGeometryType. Feature represents a thematic feature according to the definition in ISO 19109. A feature is an identifiable
and distinguishable object that is derived from the abstract GML type AbstractFeatureType. Object represents an identifiable and distinguishable object that is derived from the abstract GML type
AbstractGMLType .
Enumeration enumerates the valid attribute values in a fixed list of named literal values. Enumerations are specified inline the CityGML schema.
CodeList enumerates the valid attribute values. In contrast to Enumeration, the list of values is open and, thus, not given inline the CityGML schema. The allowed values can be provided within an external code list.
It is recommended that code lists are implemented as simple dictionaries following the GML 3.1.1 Simple Dictionary Profile cf. chapter 6.6 and chapter 10.14.
Union is a list of attributes. The semantics are that only one of the attributes can be present at any time. PrimitiveType is used for representations supported by a primitive type in the implementation.
DataType is used as a descriptor of a set of values that lack identity. Data types include primitive prede- fined types and user-definable types. A DataType is thus a class with few or no operations whose primary
purpose is to hold the abstract state of another class for transmittal, storage, encoding or persistent storage. Leaf is used within UML package diagrams to indicate model elements that can have no further subtypes.
XSDSchema is used within UML package diagrams to denote the root element of an XSD Schema contain- ing all the definitions for a particular namespace. All the package contents or component classes are placed
within the one schema. ApplicationSchema is used within UML package diagrams to denote an XML Schema definition funda-
mentally dependent on the concepts of another independent Standard within the XML Schema metalan- guage. For example, ApplicationSchema indicates extensions of GML consistent with the GML
“rules for application schemas”.
In order to enhance the readability of the CityGML UML diagrams, classes are depicted in different colors if they belong to different UML packages see Fig. 8 for an overview of UML packages. The following coloring
scheme is applied:
Classes painted in yellow belong to the UML package which is subject of discussion in that clause of the specification in which the UML diagram is given. For example, in the context of chapter 10.1
which introduces the CityGML Core module, the yellow color is used to denote classes which are de- fined in the CityGML Core UML package. Likewise, the yellow classes shown in UML diagrams in
chapter 10.3 are associated with the Building module which is subject of discussion in that chapter.
Classes painted in blue belong to a CityGML UML package different to that associated with the yellow color. In order to explicitly denote the UML package of such classes, their class names carry a
namespace prefix which is uniquely associated with a CityGML module throughout this specification cf. section 4.3 for a list of namespaces and prefixes. For example, in the context of the Building mod-
ule, classes from the CityGML Core module are painted in blue and their class names are preceded by the prefix core.
Classes painted in green are defined in GML3 and their class names are preceded by the prefix gml.
