44
2 Geomatics standards
tion of feature types like roads and buildings and their possible attributes and operations. The documentation of an application model is called an application schema.
The data model level contains the datasets and is the lowest level. In the case of
geographic information, the datasets are composed of one or many features including
their attributes and positions. The datasets are the actual data whereas the application
schema only sets the frame for the possible features.
Meta-meta model and meta model
Any consideration on modelling starts with the real world. The chosen piece of
the real world that one wishes to describe in a model is known as a universe of discourse. A first result of the modelling process is a conceptual model that describes
and limits the universe of discourse. A model is an abstract and represents only a
part of the real world. An example of the real world could be the landscape depicted
in the map in figure 2.2. A conceptual model is the list of features relevant for the
tourism-GIS in table 2.2.
A conceptual schema language provides the semantic and syntactic elements used
to rigorously describe the conceptual model and to convey consistent meaning. A
conceptual model described using a conceptual schema language is called a conceptual schema. A conceptual schema of the tourism-GIS is shown in figure 2.3. The
conceptual schema language prescribed in the ISO 19100 series is UML. The feature
types that are shown represent the semantics. The lines specif)ring the exact type of
associations are the syntactic elements. The conceptual schema language is addressed in more detail in section 3.1.1.
Application model
The application model of a GIS completely defines its data elements (classes) and
their interrelation. The heart of the application model is a detailed description of the
data structures. This description is called an application schema. The tools to describe the data structure are the feature catalogue and the General Feature Model
(GFM). The feature catalogue is a formal list ofthe feature types that are determined
as relevant and qualified for the application. The General Feature Model sets the
frame for the definition of every feature type. An example of a feature catalogue is
provided in section 3.4.2. The General Feature Model is explained in detail in section 3.2.2. Both tools have dedicated ISO 19100 standards.
An application schema also consists of components that are relevant to all feature
types. These components are the Coordinate Reference System and data quality describing elements. The Coordinate Reference System is explained in detail in section
3.2.5 and the quality aspects are addressed in section 3.2.9. Both components have
their own standards ofthe ISO 19100 family.
2 Geomatics standards
tion of feature types like roads and buildings and their possible attributes and operations. The documentation of an application model is called an application schema.
The data model level contains the datasets and is the lowest level. In the case of
geographic information, the datasets are composed of one or many features including
their attributes and positions. The datasets are the actual data whereas the application
schema only sets the frame for the possible features.
Meta-meta model and meta model
Any consideration on modelling starts with the real world. The chosen piece of
the real world that one wishes to describe in a model is known as a universe of discourse. A first result of the modelling process is a conceptual model that describes
and limits the universe of discourse. A model is an abstract and represents only a
part of the real world. An example of the real world could be the landscape depicted
in the map in figure 2.2. A conceptual model is the list of features relevant for the
tourism-GIS in table 2.2.
A conceptual schema language provides the semantic and syntactic elements used
to rigorously describe the conceptual model and to convey consistent meaning. A
conceptual model described using a conceptual schema language is called a conceptual schema. A conceptual schema of the tourism-GIS is shown in figure 2.3. The
conceptual schema language prescribed in the ISO 19100 series is UML. The feature
types that are shown represent the semantics. The lines specif)ring the exact type of
associations are the syntactic elements. The conceptual schema language is addressed in more detail in section 3.1.1.
Application model
The application model of a GIS completely defines its data elements (classes) and
their interrelation. The heart of the application model is a detailed description of the
data structures. This description is called an application schema. The tools to describe the data structure are the feature catalogue and the General Feature Model
(GFM). The feature catalogue is a formal list ofthe feature types that are determined
as relevant and qualified for the application. The General Feature Model sets the
frame for the definition of every feature type. An example of a feature catalogue is
provided in section 3.4.2. The General Feature Model is explained in detail in section 3.2.2. Both tools have dedicated ISO 19100 standards.
An application schema also consists of components that are relevant to all feature
types. These components are the Coordinate Reference System and data quality describing elements. The Coordinate Reference System is explained in detail in section
3.2.5 and the quality aspects are addressed in section 3.2.9. Both components have
their own standards ofthe ISO 19100 family.