Concept, functions, content, structure and accessibility to metadata
What are the metadata?
A Spatial Data Infrastructure (SDI) allows users to find the geographic information they need by simply searching for in the inventory of available datasets and geographic services (geoservices).
Each record in this inventory is called Metadata and describes the basic characteristics of a specific dataset or geoservice. It is used by the user to find it through the infrastructure, check its characteristics and evaluate to what extent it satisfies its needs and, if necessary, to use it later.
Therefore, datasets and geoservices must necessarily have associated some metadata in order to be accessible through the SDI.
What information do they contain?
Metadada is a description of a dataset or a geoservice that contains information about:
- The own metadata: identifier, date in which it was documented, responsible organism, standard of reference used to generate it, etc.
- The dataset or service: title, information date, responsible organism, scale or resolution, descriptive keywords, geographical and temporal extension, reference system, content, etc.
- The data quality: data origin, elaboration process, compliance with the requirements of quality described in the technical specifications, etc.
- The distribution of data and access to the service: available formats, link or information to download or to access to the service, operations supported by the service, etc.
What structure do they have? - Metadata standards
Metadata is a formal description of a dataset or geoservice based on a recognized standard, such as ISO 19115, ISO 19119, Dublin Core or DCAT.
The standards set the elements that must be described obligatorily, as well as those that are optional. They also determine the type of data to be used for each element of metadata, for example: text string, numerical types, prefixed list values, etc.
In order for users to be able to use any metadata, they must have developed according to a conceptual framework or standard that determines what their content is.
In order for a metadata file to be locatable on the Internet, this one must have been elaborated according to a set of rules of format or structured implementation standard, readable by the computers.
IDEC metadata profiles
In order to formalize and standardize metadata, the SDI Support Center has drafted guidelines that define general rules (requirements and recommendations) to follow when generating metadata, according to dataset metadata standards (ISO 19115) and of services (ISO 19119), in the scope of Catalonia. Among others, they set the minimum and mandatory information content they must include, as well as the possible optional contents.
These documents are known as:
- IDEC profile for datasets
- IDEC profile for services
Accessibility to metadata
When metadata files are accessible online (Internet), the information is available to any user who can locate and discover them by means of appropriate search mechanisms.
In order to achieve this, they are integrated into a catalog of metadata, which can be understood and operated thanks to its standardization.
IDEC, through its Support Center, makes available to users a tool to catalog metadata: the IDEC Metadata Catalogue.
The IDEC catalog is based on reference standards, both to document and generate metadata and to make them accessible through a Web Service Location -Catalogue Service for the Web (CSW)-, according to the Open Geospatial Consortium (OGC).
You will find the full description of the CSW Localization Service in the metadada of this service.