Introduction to Metadata
From DGIWG
The International Standard ISO 19115 defines metadata as ‘data about data’. This basic definition implies an unlimited scope to what can be seen as metadata. It allows some experts to see information as data or metadata with an unrealistic border between both[1]. Pragmatically, geospatial metadata can be seen as information describing spatial and, to a certain extent, non-spatial resources (as described in section 6.2), making it possible to discover, evaluate, and use available resources.
What is commonly understood as metadata comprises:
- Identification information, i.e. information to uniquely identify the resource such as:
- Title, abstract, reference dates, version, purpose, responsible parties, …
- Data extent,
- Browse graphics (overview, thumbnail, …),
- Possible usage;
- Content Description, i.e. information identifying the feature catalogue(s) used and/or information about the coverage content;
- Distribution information, i.e. information about the distributor of, and options for obtaining the resource;
- Legal and security constraints; i.e. restrictions placed on the data and metadata in the context of delivering, accessing and using.
- Portrayal information, i.e. information identifying the portrayal catalogue used;
- Reference system information, i.e. identification of the spatial and temporal system(s) used in the resource data;
- Spatial Representation, i.e. information concerning the mechanisms used to spatially represent the resource data;
- Quality and validity information, i.e. a general assessment of the quality of the resource data including:
- quality measures related to the geometric, temporal and semantic accuracy, the completeness or the logical consistency of the data;
- lineage information including the description of the sources and processes applied to the sources;
- validity information related to the range of space and time pertinent to the data; to whether the data has been checked to a measurement or performance standard or to what extent the data is fit for purpose.
- Maintenance information, i.e. information about the scope and frequency of updating of the resource data.
- Information about metadata, i.e. identifier for the metadata itself, information about the language and character set of the metadata, metadata date stamp, metadata point of contact, name and version of the metadata standard, …
A general use case described in section 7 defines the three major activities involving metadata: discovery, evaluation and use of the associated data. A prerequisite is the establishment and maintenance of metadata, i.e. the overall management of the metadata resources. This document does not define the way in which metadata resources are to be managed, but rather how the metadata resources are to be applied to address discovery, evaluation, and use.
