It describes the who, what, when, where, why and how for data.
It’s important because it’s the record we rely on to find out how it was created.
That’s why it has to be detailed, dependable and well-documented.
Let’s explore step-by-step the anatomy of metadata.
Here’s the necessary stuff you have to incorporate in metadata.
Identification provides a brief narrative of your data. It summarizes the purpose of your data in a succinct way. For example, identification assigns a title, description and keywords to your metadata. By adding keywords, it helps categorize your data with predefined taxonomy.
Contact information includes an originator, publisher and distributor. The originator is who developed the data set. Next, the publisher assists in producing, editing and finalizing the end-product. Finally, the distributor’s main focus is making the data available.
Quality explains the accuracy and standards the data set followed. For example, the horizontal and vertical position accuracy evaluates the ground position quality. Tests of quality include the completeness, integrity and inspections of the data.
4 Spatial Reference
Spatial reference information assigns a geographic extent and coordinate system. Projection information includes a projection, datum and units. For example, UTM Zones and State Plane are common coordinate systems. Geographic extent comes in the form of a bounding box, place keyword or thumbnail.
5 Entity and Attribute
Entities refer to the map data type such as points, line, polygons or grids.The purpose of this metadata item is to describe how the spatial information in the data is represented. For the entity attributes, it includes a description with a list of valid values and domains.
Lineage describes in detail how the dataset was constructed. For example, it lists the processing steps and responsible parties. Each processing step has a date when it took place so users can track changes. It’s like a changelog listing the evolution of the data from start to finish.
The legal section outlines the constraints for accessing and distributing the data. It describes the liability to assure protection of privacy and intellectual property. Metadata includes a security classification which handles the restriction over security concerns. For example, confidential, restricted, sensitive, unrestricted and unclassified are examples of security classification in metadata.
Temporal information focuses on when the data were collected or updated and how long it’s valid for. It also states the progress such as when future updates are scheduled. The frequency of updates can be anywhere from daily, weekly, monthly or annually.
9 Metadata Reference
The metadata reference section is specific to the metadata. It gives a point of contact when there are uncertainties such as how to cite information when used. The metadata reference has a temporal component for the date it was created and when it will be revised next.
10 Metadata Standard
For GIS metadata standards, geographic data providers follow guidelines from the Federal Geographic Data Committee (FGDC), ISO 19115, EPA, Esri, Inspire and MEDIN. Each schema was developed to best suit their particular requirements and needs. More on this later.
Metadata as XML
Remember that metadata is just a XML file. Each metadata standard follows a specific schema and markup.
Any text editor can open XML files. When you open a metadata file, it incorporates all the key elements in the markup.
<origin>National Aeronautics and Space Administration (NASA)</origin> <pubdate>2019/05/15</pubdate>
From these two blocks of XML code, you can find that NASA is the originator. Also, the data was published on May 5th, 2019.
Types of Metadata
Several committees from around the world have developed their own guidelines for metadata. In terms of GIS metadata, the most common are as follows: