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Metadata in Spatial Data Management

What is Metadata?

Metadata, commonly defined as "data about data" or "information about data", is a structured set of information which describes data (including both digital and non-digital datasets) stored in administrative systems. Metadata may provide a short summary about the content, purpose, quality, location of the data as well as information related to its creation.

What are Metadata Standards?

Metadata standards provide data producers with the format and content for properly describing their data, allowing users to evaluate the usefulness of the data in addressing their specific needs.

The standards provide a documented, common set of terms and definitions that are presented in a structured format.

Why do we need Standardised Metadata?

Standardised metadata support users in effectively and efficiently accessing data by using a common set of terminology and metadata elements that allow for a quick means of data discovery and retrieval from metadata clearinghouses. The metadata based on standards ensure information consistency and quality and avoid that important parts of data knowledge are lost.

Geographic Information Metadata Standard

Geographic data, which can be defined as any data with a geographic component, is often produced by one individual or organisation, and may address the needs of various users, including information system analysts, programme planners, developers of geographic information or policy makers. Proper standard documentation on geographic data enable different users to better evaluate the appropriateness of data to be used for data production, storage, update.

The metadata standards supported by GeoNetwork opensource are the ISO 19115:2003 -approved by the international community in April 2003 as a tool to define metadata in the field of geographic information - and the FGDC - the metadata standard adopted in the United States by the Federal Geographic Data Committee. In addition, GeoNetwork opensource supports also the international standard Dublin Core for the description of general documents.

This ISO Standard precisely defines how geographic information and related services should be described, providing mandatory and conditional metadata sections, metadata entities and metadata elements. This standard applies to data series, independent datasets, individual geographic features and feature properties. Despite ISO 19115:2003 was designed for digital data, its principles can be extended to many other forms of geographic data such as maps, charts, and textual documents as well as non-geographic data.

The underlying format of an ISO19115:2003 compliant metadata is XML. GeoNetwork uses the ISO Technical Specification 19139 Geographic information - Metadata -XML schema implementation for the encoding of this XML.

Metadata profiles

A metadata profile is an adaptation of a metadata standard to suit the needs of a community. For example, the ANZLIC profile is an adaptation of the ISO19115/19139 metadata standard for Australian and New Zealand communities. A metadata profile could be implemented as:

  • a specific metadata template that restricts the fields/elements a user can see with a set of validation rules to check compliance
  • all of the above plus new fields/elements to capture concepts that aren't in the basic metadata standard

Building a metadata profile is described in the Schema Plugins section of the GeoNetwork Developers Manual. Using this guide and the GeoNetwork schema plugin capability, a profile can be built by an experienced XML/XSL software engineer.

Transition between metadata standards

With the ISO19115:2003 Metadata standard for Geographic Information now being the preferred common standard, many have a need to migrate legacy metadata into the new standard.

GeoNetwork provides import (and export) functionality and has a number of transformers in place. It is an easy process for a system administrator to install custom transformers based on XSLT.