What is ISO 19136-1 about?
The Geography Markup Language (GML) is an XML encoding in accordance with ISO 19118 for the transport and storage of geographic information modelled in accordance with the conceptual modelling framework used in ISO 19136-1 of International Standards and including both the spatial and non-spatial properties of geographic features.
ISO 19136-1 defines the XML Schema syntax, mechanisms and conventions that:
- Provide an open, vendor-neutral framework for the description of geospatial application schemas
- For the transport and storage of geographic information in XML
- Allow profiles that support proper subsets of GML framework descriptive capabilities
- Support the description of geospatial application schemas for specialized domains and information communities
- Enable the creation and maintenance of linked geographic application schemas and datasets
- Support the storage and transport of application schemas and datasets
- Increase the ability of organizations to share geographic application schemas and the information they describe.
Implementers can decide to store geographic application schemas and information in GML, or they can decide to convert from some other storage format on demand and use GML only for schema and data transport.
NOTE- If an ISO 19109 conformant application schema described in UML is used as the basis for the storage and transportation of geographic information, this document provides normative rules for the mapping of such an application schema to a GML application schema in XML Schema and, as such, to an XML encoding for data with a logical structure in accordance with the ISO 19109 conformant application schema.
Who is ISO 19136-1 for?
ISO 19136-1 on Geography Markup Language (GML) is useful for:
- Geographic information department
- Companies that use GML for Geographic information
- Transport and logistic companies
Why should you use ISO 19136-1?
The number of properties a feature may have, together with their names and types, is determined by its type of definition. Geographic features with geometry are those with properties that may be geometry value.
A feature collection is a collection of features that may itself be regarded as a feature, as a consequence a feature collection has a feature type and thus may have distinct properties of its own, in addition to the features it contains.
A GML application schema is specified in XML Schema and can be constructed in two different and alternative ways:
- By adhering to the rules specified in ISO 19109 for application schemas in UML, and conforming to both the constraints on such schemas and the rules for mapping them to GML application schemas specified in this document
- By adhering to the rules for GML application schemas specified in this document for creating a GML application schema directly in XML Schema.
ISO 19136-1 is valuable for the users because it supports both the ways. To ensure proper use of the conceptual modelling framework of the ISO 19100 series of International Standards, all application schemas are expected to be modelled in accordance with the General Feature Model as specified in ISO 19109. Within the ISO 19100 series, UML is the preferred language by which to model conceptual schemas.
GML specifies XML encodings, conformant with ISO 19118, of several of the conceptual classes defined in the ISO 19100 series of International Standards and the OpenGIS Abstract Specification. These conceptual models include those defined in:
- ISO/TS 19103 — Conceptual schema language (units of measure, basic types)
- ISO 19107 — Spatial schema (geometry and topology objects)
- ISO 19108 — Temporal schema (temporal geometry and topology objects, temporal reference systems)
- ISO 19109 — Rules for application schemas (features)
- ISO 19111 — Spatial referencing by coordinates (coordinate reference systems)
- ISO 19123 — Schema for coverage geometry and functions
The aim of ISO 19136-1 is to provide a standardized encoding (i.e., a standardized implementation in XML) of types in the conceptual models specified by the International Standards listed above. If every application schema were encoded independently and the encoding process included the types from, for example, ISO 19108, then, without unambiguous and completely fixed encoding rules, the XML encodings would be different. Also, since every implementation platform has specific strengths and weaknesses, it is helpful to standardize XML encodings for core geographic information concepts modelled in the ISO 19100 series of International Standards and commonly used in application schemas.
What’s changed since the last update?
BS EN ISO 19136-1:2020 supersedes BS EN ISO 19136:2009. BS EN ISO 19136-1:2020 includes some technical changes with respect to BS EN ISO 19136:2009. These include:
- The XML attribute gml:id in gml: AbstractGMLType has been made optional
- The elements gml: AbstractRing and gml: Shell have been added to the substitutionGroups gml AbstractCurve and gml: AbstractSurface respectively
- The types gml: AbstractRingType and gml: ShellType are now extended from base types gml
- AbstractCurveType and gml: AbstractSurfaceType respectively.