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Describe / Metadata > Data Dictionaries
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U.S. Geological Survey Data Lifecycle Diagram

Data Dictionaries

A data dictionary contains structured data names defining and describing the data resource.

Definition: Data Dictionary

Key Points

  • A Data Dictionary is a repository of information that defines and describes a data resource.
  • A Thesaurus is a structured list of preferred terms around a subject.
  • Use widely known keywords and tags for your data in order to make your data more searchable and discoverable.
  • Find preferred terms and keywords with a thesaurus (e.g., USGS Biocomplexity Thesaurus).

According to the DOI Data Management Guide [PDF] (2008), a data dictionary is a repository of data (metadata) defining and describing the data resource.

Data Dictionary Definitions


Entity: Fish Measurements - A sample of the physical measurements of rainbow trout in Lake Superior, MN collected on 07/14/2010.


  • Attribute Type: fish_totl
  • Attribute Definition: Fish Total Length - Measured total length (cm) of the fish from mouth to tip fin. Mouth shut and fin pinched closed.
  • Domain Range: 0.00-300.00;
    -999 = NA

Entity definitions:

  • Defines a person, place, or thing about which data can be stored
  • Must be clearly understood before attributes can be named or defined

Data element (attribute) definitions:

  • Describe the inherent nature of the data
  • NOT the entity that the attribute contains information about
  • NOT the uses of the data (where, when, how, or by whom)
  • NOT the codes and values the codes represent


Example USGS Data Dictionaries

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