Definition
1. Metadata is data (information) that provides information about other data.
2. Three distinct types of metadata exist: structural metadata, descriptive metadata, and administrative metadata.
3. Metadata means "data about data". Although the "meta" prefix (from the Greek preposition and prefix μετά-) means "after" or "beyond", it is used to mean "about" in epistemology. Metadata is defined as the data providing information about one or more aspects of the data; it is used to summarize basic information about data which can make tracking and working with specific data easier. Some examples include: Means of creation of the data, Purpose of the data, Time and date of creation, Creator or author of the data, Location on a computer network where the data was created, Standards used, File size
Abbreviation
Synonyms
Superterms
Subterms
Sources
http://www.merriam-webster.com/dictionary/metadata, http://marciazeng.slis.kent.edu/metadatabasics/types.htm, https://en.wikipedia.org/wiki/Metadata#Definition
Metadata in oedb
In the oedb, the metadata is stored in a comment as a JSON string.
The SQL example is on GitHub.
Different concepts for metadata were compared, harmonized and simplyfied:
-- metadata description
COMMENT ON TABLE model_draft.test_table IS '{
"title": "Good example title",
"description": "example metadata for example data",
"language": [ "eng", "ger", "fre" ],
"reference_date": "2016-01-01",
"sources": [
{"name": "eGo dataprocessing", "description": "", "url": "https://github.com/openego/data_processing", "license": "GNU Affero General Public License Version 3 (AGPL-3.0)", "copyright": "© Reiner Lemoine Institut"},
{"name": "", "description": "", "url": "", "license": "", "copyright": ""} ],
"spatial": [
{"extent": "europe",
"resolution": "100 m"} ],
"temporal": [
{"start": "2017-01-01",
"end": "2017-12-31",
"resolution": "hour"} ],
"license": [
{"id": "ODbL-1.0",
"name": "Open Data Commons Open Database License 1.0",
"version": "1.0",
"url": "https://opendatacommons.org/licenses/odbl/1.0/",
"instruction": "You are free: To Share, To Create, To Adapt; As long as you: Attribute, Share-Alike, Keep open!",
"copyright": "© Reiner Lemoine Institut"} ],
"contributors": [
{"name": "Ludee", "email": "", "date": "2016-06-16", "comment": "Create metadata"},
{"name": "Ludee", "email": "", "date": "2016-11-22", "comment": "Update metadata"},
{"name": "Ludee", "email": "", "date": "2016-11-22", "comment": "Update header and license"},
{"name": "Ludee", "email": "", "date": "2017-03-16", "comment": "Add license to source"},
{"name": "Ludee", "email": "", "date": "2017-03-28", "comment": "Add copyright to source and license"},
{"name": "Ludee", "email": "", "date": "2017-05-30", "comment": "Update metadata to version 1.3"} ],
"resources": [
{"name": "model_draft.test_table",
"format": "sql",
"fields": [
{"name": "id", "description": "Unique identifier", "unit": "" },
{"name": "year", "description": "Reference year", "unit": "" },
{"name": "value", "description": "Example value", "unit": "MW" },
{"name": "geom", "description": "Geometry", "unit": "" }] }],
"metadata_version": "1.3"}';
-- select description
SELECT obj_description('model_draft.test_table' ::regclass) ::json;
