Properties

Extension Title

Properties

Introduction

This extension stores GeoPackage properties as key-value pairs and mappings (multiple values per key). All properties are permitted and pre-defined properties enable discovery of commonly defined metadata.

Extension Author

National Geospatial-Intelligence Agency, author_name nga

Extension Name or Template

nga_properties

Extension Type

New Requirement

Applicability

This extension applies to a custom attributes user table (2.4).

Scope

Read-write

Requirements

GeoPackage

Extension Table Entry

The Properties extension is registered into the gpkg_extensions table as follows:

`gpkg_extensions`
table_name	column_name	extension_name	definition	scope
nga_properties		nga_properties	URL to this extension description	read-write

Properties Attributes Table

The Properties Attributes Table defines an id, property, and value column. The property and value columns store key-value pairs and mappings. A unique constraint prevents duplicate property-value entries. Values may be any data type but are stored as TEXT.

`nga_properties`
Column Name	Type	Description	Null	Key
id	INTEGER	Autoincrement primary key	no	PK
property	TEXT	Property name or key to a value or set of values	no
value	TEXT	Property value	yes


CREATE TABLE nga_properties (
	id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
	property TEXT NOT NULL,
	value TEXT,
	UNIQUE (property, value)
);

Contents Entry

The Properties Attributes Table defines a Contents row (2.4.2).

`gpkg_contents`
table_name	data_type	identifier	description	last_change	min_x	min_y	max_x	max_y	srs_id
nga_properties	attributes	nga_properties		date of last change

GeoPackage SQLite Configuration

None

GeoPackage SQLite Extension

None

Pre-defined Properties

The following pre-defined list of properties define common metadata terms, most taken from the Dublin Core Metadata Initiative.

Pre-defined Properties
Property	Definition
contributor	An entity responsible for making contributions to the resource
coverage	The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant
created	Date of creation of the resource
creator	An entity primarily responsible for making the resource
date	A point or period of time associated with an event in the lifecycle of the resource
description	An account of the resource
identifier	An unambiguous reference to the resource within a given context
license	A legal document giving official permission to do something with the resource
modified	Date on which the resource was changed
publisher	An entity responsible for making the resource available
references	A related resource that is referenced, cited, or otherwise pointed to by the described resource
relation	A related resource
source	A related resource from which the described resource is derived
spatial	Spatial characteristics of the resource
subject	The topic of the resource
tag	A tag or label of the resource
temporal	Temporal characteristics of the resource
title	A name given to the resource
type	The nature or genre of the resource
URI	The set of identifiers constructed according to the generic syntax for Uniform Resource Identifiers as specified by the Internet Engineering Task Force
valid	Date (often a range) of validity of a resource
version	A version of the resource

Examples

The rivers GeoPackage defines properties including: title, creator, contributor, source, URI, and tag

The example GeoPackage defines properties including: title, version, creator, publisher, contributor, created, date, modified, description, identifier, license, source, subject, type, URI, and tag