OpenGIS® Implementation Specification, 20 February 2001

OGC Document Number: 01-029

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Simon Cox (CSIRO Exploration & Mining) <>

Adrian Cuthbert (SpotOn MOBILE) <>

Ron Lake (Galdos Systems, Inc.) <>

Richard Martell (Galdos Systems, Inc.) <>


Simon Cox (CSIRO Exploration & Mining) <>

Adrian Cuthbert (SpotOn MOBILE) <>

Paul Daisey (U.S. Census Bureau) <>

John Davidson (OGC IP2000 Team) <>

Sandra Johnson (MapInfo Corporation) <>

Edric Keighan (Cubewerx Inc.) <>

Ron Lake (Galdos Systems Inc.) <>

Marwa Mabrouk (ESRI Ltd.) <>

Serge Margoulies (IONIC Software) <>

Richard Martell (Galdos Systems, Inc.) <>

Lou Reich (NASA/CSC) <>

Barry O'Rourke (Compusult Ltd.) <>

Jayant Sharma (Oracle Corporation) <>

Panagiotis (Peter) Vretanos (CubeWerx Inc.) <>

Copyright © 2001 OGC, All Rights Reserved.


The Geography Markup Language (GML) is an XML encoding for the transport and storage of geographic information, including both the spatial and non-spatial properties of geographic features. This specification defines the XML Schema syntax, mechanisms, and conventions that

  • Provide an open, vendor-neutral framework for the definition of geospatial application schemas and objects;

  • 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 data sets;

  • Increase the ability of organizations to share geographic application schemas and the information they describe.

Implementers may decide to store geographic application schemas and information in GML, or they may decide to convert from some other storage format on demand and use GML only for schema and data transport.

Document status

This document is an OpenGIS® Implementation Specification.

XML instances which are compliant to this specification shall validate against a conforming application schema. A conforming application schema shall import the Geometry Schema (geometry.xsd), the Feature Schema (feature.xsd), and the XLinks schema (xlinks.xsd) as base schemas; furthermore, it shall be developed using the rules for the development of application schemas specified in section 5 of this document.

Sections 1 and 2 of this document present the background information and modeling concepts that are needed to understand GML. Section 3 presents the GML conceptual model which is independent of encoding. Section 4 presents material which discusses the encoding of the GML conceptual model using the XML Schema definition language (XSDL). This material is intended to demonstrate how to employ the normative GML geometry and feature schemas specified in Appendices A and B of this document. Section 5 of this document presents the rules for the development of conformant GML application schemas. Section 6 presents examples to illustrate techniques for constructing compliant GML application to model recurring geographic themes; these techniques are not normative but they do represent the collective experience of the editors of this document and are strongly recommended. Conforming profiles of this document shall be developed according to the rules specified in section 7. Appendix A presents the Geometry schema, Appendix B presents the Feature schema, and Appendix C presents the XLinks schema.

The OpenGIS Consortium (OGC) invites comments on this Implementation Specification?please submit them to

Table of Contents

1 Representing geographic features

1.1 Introduction

1.2 Feature and Geometry models

2 Overview of GML

2.1 Design goals

2.2 Schemas for geospatial data

2.3 Graphical rendering

3 Conceptual framework

3.1 Features and properties

3.2 Geometric properties

3.3 Application schemas

4 Encoding GML

4.1 Introduction

4.2 Encoding features without geometry

4.3 Encoding geometry

4.4 Encoding features with geometry

4.5 Encoding feature collections

4.6 Encoding feature associations

5 GML application schemas

5.1 Introduction

5.2 Rules for constructing application schemas (normative)

6 Worked examples of application schemas (non-normative)

7 Profiles of GML

Appendix A: The Geometry schema, v2.06 (normative)

Appendix B: The Feature schema, v2.06 (normative)

Appendix C: The XLinks schema, v2.01 (normative)

Appendix D: References

Appendix E: Revision history