88
3 Non-geometry standards
Steps 3 and 4 use general Information Technology transfer services to send and
receive data.
Steps 1 and 6, the internal translations within the source and destination systems,
are outside the scope of this standard.
SystemA
System B
Internal schema
Internal schema
i 11
Common applicatlon schema <;;~~~~~~ Common application schema
11
enaxled dataset step3
general rr
transfer service
Ln
il
Step 4 encoded dataset
Fig. 3.17. Model for the data exchange, simplified (lS050 2002)
Encoding using the Extensible Markup Language (XML)
As the Extensible Markup Language (XML) is recommended for the data exchange, the ISO 19118 (Encoding) defines a mapping for application schemas that
are written in the Unified Model\ing Language (UML) to the corresponding data
structures of XML. There are two views to that mapping:
1. The abstract view is independent from any dataset. This is the application
schema. It contains the c1asses and other components, such as attributes and associations, that ful\y describe all geographie feature types belonging to a certain application and their relations. A representation of the application schema is a feature catalogue. In XML the application schema is expressed as a Document Type
Dec1aration (DTD) or as an XML schema document (XSD). 80th contain the
rules according to which an XML document has to be built.