Dictionary (Flat Vocabulary)

Definition of Dictionary

In the context of metadata, a dictionary is a type of controlled flat vocabulary, which provides a list of metadata terms, definitions and additional information within a specific domain.

Discussion

The idea of a dictionary in the context of metadata is somewhat vague. Just as there was no definition of "dictionary" in Webster's original dictionary for the English language, there is no formal definition of a metadata dictionary. In practice, a dictionary builds upon a glossary by providing additional information about each value. This additional information might include how the value came to be selected, the etymology of the value, or additional site-specific context for each value. The main purpose of a dictionary is to provide more than a definition - but the "more" is subject to individual projects' interpretation.

Example - CDI Sea Search (SeaDataNet) Vocabularies

"CODE","SHORT_TITLE","FULL_TITLE","COMMENTS","CREATED","MODIFIED"
"USPC","Unspec.","Not specified","Use for parameters where the units are deliberately undefined such as arbitrary units","2/2/05 16:14",""
"UKWN","Unknown","Not known","Use for parameters that should have a unit, but it is not known. Usage of this code is STRONGLY DISCOURAGED","2/2/05 16:16",""
"UPPM","ppm","Parts per million","Usage not recommended for parts per million by weight. Use milligrams/kilogram instead.","16/9/1994 00:00:00","18/10/1995 13:36:11"
"UAQU","A^2/Q","Angstrom squared per quanta","Scaled unit by Avagadro's number and powers of ten to m**2/mol","2/2/05 16:49",""
"USVD","Sv","Sverdrup","One Sverdrup is a million cubic metres per second or a million cumecs","17/2/2005 12:44:16","14/10/2005 11:47:50"
"UNPI","ng","Nanograms","Changed from nanograms per individual when per individual semantics transferred to the parameter description","10/2/00 0:00","3/8/05 8:52"
"UAAA","deg","Degrees","","1/1/87 0:00","4/11/05 12:47"
"UABB","deg T","Degrees True","","1/1/87 0:00","4/11/05 12:47"

In this dictionary, we are provided with a code, short title, full title, comments, creation date and modification date, in csv format. Notice this dictionary clearly tells us about the management of this vocabulary. This type of information is very useful while you are selecting a vocabulary. Many of the creation or modification dates are in 2005, so this shows that the list is very actively managed.