GB/T 23708.2-2023Geographic information - Geography Markup Language(GML) - Part 2: Extended schemas and encoding rules (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents" Drafting.

This document is Part 2 of GB/T 23708 "Geographic Information Geographic Markup Language (GML)". GB/T 23708 has been released the following parts.

---Part 2: Extended patterns and encoding rules.

This document is equivalent to ISO 19136-2:2015 "Geographic Information Geographic Markup Language (GML) Part 2: Extension Schema and Coding Code Rules".

Compared with ISO 19136-2:2015, in terms of document structure, the original Chapter 2 has been adjusted to Chapter 4 of this document.

This document has made the following minimal editorial changes.

---GML3.2 in the original international standard document is replaced by GB/T 23708-2009, and GML3.3 in the original international standard document Use "this document" instead.

Please note that some content in this document may be subject to patents. The publisher of this document assumes no responsibility for identifying patents.

Introduction

Geography Markup Language (GML) is an XML syntax expressed in XML Schema, used to describe application schemas as well as transmission and storage Geographic information.

GB/T 23708 aims to provide XML syntax, data types and structures for describing application patterns and transmitting and storing geographical information.

Consists of 2 parts.

---Part 1: Basics. The purpose is to provide basic geographic information models (such as geographic features, space, time and coordinate reference systems Patterns, etc.) grammar and coding rules.

---Part 2: Extended patterns and encoding rules. The purpose is to provide geographic information expansion patterns (such as irregular triangulation, linear Reference and reference grid patterns, etc.) grammar and coding rules.

Key concepts in geomarkup languages for real-world modeling are derived from the ISO 19100 series of standards and the OpenGIS abstract specification.

An element is "an abstraction of some phenomenon in the real world" (ISO 19101). If a feature corresponds to a location on Earth, then it is a geographical element. Therefore, a digital representation of the real world can be viewed as a collection of elements. The status of an element consists of a set of special Characteristic definition, each characteristic can be defined by a triplet of {name, type, value}.

The number of attributes per feature and the name and type of each feature are determined by the type of feature. Geographic features have geometric properties elements. A feature set is a collection of multiple features, which itself can also be regarded as a feature. Therefore, a feature set has a feature type.

At the same time, in addition to the characteristics of the elements it contains, it also has its own characteristics.

According to ISO 19109, the element types of an application or application domain are usually defined in the application schema. A GML application schema is A specific XML schema can be constructed in one of two ways.

---By adopting the UML application pattern rules specified in ISO 19109, complying with the constraints of the pattern and mapping them to this document Rules for GML application schema;

---Create a GML application expressed directly in XML schema by adopting the GML application schema rules specified in this document model.

This document supports both methods. In order to ensure the correct use of the conceptual model framework in the ISO 19100 series of standards, all application models the modeling is consistent with the common element model in ISO 19109.In the ISO 19100 series of standards, it is recommended to use UML as a concept A language for pattern modeling.

Consistent with ISO 19118, GML specifies a number of conceptual classes defined in the ISO 19100 series of standards and the Open GIS Abstract Specification.

XML encoding. The definitions of these conceptual models are contained in the following standards.

---ISO 19103:2015 Conceptual pattern language (units of measurement, basic types);

---ISO 19107:2019 Spatial patterns (geometric and topological objects);

---ISO 19108:2002 time mode (time geometry and topological objects, time reference system);

---ISO 19109:2015 Rules (elements) for geographic information application models;

---ISO 19111:2019 Coordinate-based spatial reference (coordinate reference system)

---ISO 19123:2005 Geographic information covering geometric and functional patterns;

---ISO 19148:2021 Linear referencing of geographical information.

The purpose of this document is to provide the relevant types and standard encodings (i.e. standard XML implementation) of the conceptual models specified in the above-mentioned international standards.

It is assumed that each application mode is coded independently and that the code includes types derived from e.g. GB/T 22022.Without accurate and fully fixed According to certain encoding rules, the XML encoding will be different. At the same time, since each implementation platform has specific advantages and disadvantages, ISO it is necessary to standardize the XML encoding of the core geographic information conceptual models defined in the 19100 series of standards, and these concepts Models are also commonly used in application patterns.

In most cases, the mapping from a conceptual class is straightforward; in some cases, the mapping is more complex (a detailed description of the mapping is part of this document).

Additionally, GML provides XML for other concepts not yet modeled in the ISO 19100 series of standards and the OpenGIS abstract specification.

Encoding, such as dynamic features, simple observations or value objects.

Predefined geographic feature types in GML include coverage and simple observation.

Cover is a subtype of feature that has a cover function that takes into account the space and time domain and a set of numbers that describe homogeneous 1 to n-dimensional objects.

collection of values. A coverage can be an element or a collection of elements, "used to construct spatial relationships and spatial distributions among earth phenomena.

Modeling and Visualization" (OGC Abstract Specification Topic 6). Covers "As a function, returns a value in the range corresponding to its position in the space-time domain.

value" (ISO 19123).

Observation is used to model observation behavior, which usually includes a camera or some other program and a person or some Other Instruments [Merriam-Webster Dictionary. "The act of recognizing and recording facts or events often involving the use Instruments make measurements"]. An observation is considered a GML element with an observation time and an observation value.

A frame of reference provides a metric for determining location, time, or other descriptive quantitative or qualitative values.

A coordinate reference system consists of a set of coordinate axes related to the Earth through datums, which define the size and shape of the Earth.

A time frame of reference provides a standard unit for measuring time and describing its length or duration.

The Reference Systems Dictionary provides definitions of the use of reference systems in space or time geometry.

Spatial geometry is the value of spatial feature properties. They specify the coordinate reference system in which measurements are made. The "parent" of a geometric complex or geometric aggregation A geometric element specifies a coordinate reference system for its constituent elements.

Temporal geometry is the value of the temporal feature properties. Like its spatial counterpart, the geometry of time specifies the temporal frame of reference in which measurements are made.

Spatial or temporal topology is used to represent various topological relationships between elements.

The Dictionary of Measurement Units provides numerical measurement definitions of physical quantities such as length, temperature, and pressure, as well as conversions between measurement units.

Geographic Information Geographic Markup Language (GML) Part 2: Extended patterns and coding rules

1 Scope

Geographic Markup Language (GML) is an XML encoding consistent with ISO 19118 for transmitting and storing data according to the ISO 19100 series of standards.

The conceptual model framework is adopted to model the geographical information, including the spatial and non-spatial characteristics of geographical elements.

This document specifies XML schema syntax, mechanisms, and conventions, including.

--- Provide an open, neutral framework for describing geospatial application models, which can transmit and store geographic information in XML format;

---Enables dedicated standards to select appropriate subsets with GML framework description capabilities;

---Support specific fields and information groups to describe geospatial application models;

--- Geographical application schemas and datasets used to create and maintain links;

---Supports storage and transmission of application schemas and data sets;

---Improve the ability to share geographic application models and the information they describe.

Implementers can specify whether to use GML to store geographic application schemas and information, or to convert from other storage formats as needed, or it can be specified that only GML is used to transport the schema and data.

This document is based on GB/T 23708-2009 and extends the model components and requirements.

Note. Consistent with the application model described in UML form in ISO 19109, as the basis for transmitting and storing geographical information, this document provides Standard rules for mapping to GML application schemas expressed as XML schemas, and description of structured data consistent with ISO 19109 application schemas the XML encoding of the data.

2 Normative reference documents

The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, the dated quotations for undated referenced documents, only the version corresponding to that date applies to this document; for undated referenced documents, the latest version (including all amendments) applies to this document.

GB/T 23708-2009 Geographic Information Geographic Markup Language (GML) (ISO 19136:2007, IDT) Note. GB/T 7408-2005 Data elements and exchange formats Information exchange date and time representation (ISO 8601:2000, IDT) ISO/IEC 13249-3:2011 Information technology database language SQL multimedia and application package Part 3: Spatial (Infor-))

1) This document corresponds to OGC document 09-144r1.Until the final publication of this international standard, the MIME media type is still in the IETF/IANA registration process.

Therefore, this reference is undated so that the most recent media type after registration can refer to this document.