3.2 Basic standards
87
3.2.7 Encoding (ISO 19118)
The concept of the exchange of geographie information datasets is standardised in
the ISO 19118 (Encoding). It defines a system-independent data structure for transport and storage and recommends the usage of the Extensible Markup Language
(XML) for encoding. XML shall become a normative part of the ISO 19118 as soon
as another standard of the ISO 19100 family, the ISO 19136 (Geography Markup
Language), is accepted as mature.
The primary goal of the ISO 19100 family of standards is to enable full interoperability between heterogeneous geographie information systems. To achieve this
goal, two fundamental issues need to be resolved. The first issue is to define the semantics of the content and the logical structures of geographie data. This is achieved
by implementing the same application schema. The second issue is to define a system and platform independent data structure that can represent data corresponding to
the application schema.
For example, equal semantics and logical structures can be guaranteed by using
the same feature catalogue in the two systems involved. A system and platform independent data exchange format has to be created according to the ISO 19118
(Encoding).
Model for the data exchange
The generic model for the data exchange assumes two systems that run on different
computer platforms and have different application schemas. The transfer of a dataset
between such systems is modelled in six steps.
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Step 6:
The source system translates its internal data into a data structure that is
according to the common application schema.
An encoding service applies the encoding rules to the data, creating a file
or transferring the data to a transfer service.
The source system invokes a transfer service to send the encoded dataset
to the destination system.
The destination system receives the dataset.
The destination system applies the inverse encoding rule to interpret the
encoded data.
The destination system must translate the application schema specific data
into its internal database.
Steps 2 and 5 are standardised in ISO 19118 that describes the encoding and the
decoding of the dataset. These two steps are handled by an encoding service that is a
software component that implements the encoding rule and provides an interface to
encoding and decoding functionality.
The encoding rule specifies the data types to be converted as weIl as the syntax
structure and coding schemes used in the resulting data structure, preferably an
XML-document.
87
3.2.7 Encoding (ISO 19118)
The concept of the exchange of geographie information datasets is standardised in
the ISO 19118 (Encoding). It defines a system-independent data structure for transport and storage and recommends the usage of the Extensible Markup Language
(XML) for encoding. XML shall become a normative part of the ISO 19118 as soon
as another standard of the ISO 19100 family, the ISO 19136 (Geography Markup
Language), is accepted as mature.
The primary goal of the ISO 19100 family of standards is to enable full interoperability between heterogeneous geographie information systems. To achieve this
goal, two fundamental issues need to be resolved. The first issue is to define the semantics of the content and the logical structures of geographie data. This is achieved
by implementing the same application schema. The second issue is to define a system and platform independent data structure that can represent data corresponding to
the application schema.
For example, equal semantics and logical structures can be guaranteed by using
the same feature catalogue in the two systems involved. A system and platform independent data exchange format has to be created according to the ISO 19118
(Encoding).
Model for the data exchange
The generic model for the data exchange assumes two systems that run on different
computer platforms and have different application schemas. The transfer of a dataset
between such systems is modelled in six steps.
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Step 6:
The source system translates its internal data into a data structure that is
according to the common application schema.
An encoding service applies the encoding rules to the data, creating a file
or transferring the data to a transfer service.
The source system invokes a transfer service to send the encoded dataset
to the destination system.
The destination system receives the dataset.
The destination system applies the inverse encoding rule to interpret the
encoded data.
The destination system must translate the application schema specific data
into its internal database.
Steps 2 and 5 are standardised in ISO 19118 that describes the encoding and the
decoding of the dataset. These two steps are handled by an encoding service that is a
software component that implements the encoding rule and provides an interface to
encoding and decoding functionality.
The encoding rule specifies the data types to be converted as weIl as the syntax
structure and coding schemes used in the resulting data structure, preferably an
XML-document.