Parameters

Definition

Syntax

Group: Parameters 
    Category: [Category Valid]
    Topic: [Topic Valid]
    Term: [Term Valid]
    Variable: [Variable Valid]
    Detailed_Variable: [text line]
End_Group

Specifications

• Required field.
• May be repeated as often as necessary.
• Parameters include Categories, Topics, Terms, Variables, and Detailed Variables.
• Within the group, Category, Topic and Term are required, whereas Variable and Detailed Variable are not.
• Categories, Topics, Terms and Variables must be selected from the Parameter Valids: see Appendix A. DIFs submitted from CIESIN or UNEP may be keyed with CIESIN or INFOTERRA parameters, respectively. All others must be keyed with GCMD Earth Science parameters.
• No valids are maintained for Detailed Variables. This is a free-text line which may contain up to 80 characters of the printable ASCII character set. Specific data set parameters may be entered as desired.
• Only one Category/Topic/Term/Variable/Detailed Variable combination may be specified per group.

Recommendations

• All applicable parameters should be specified. Remember to look at the entire list of parameters to determine whether a Variable is repeated under more than one Topic or Term. If so, a decision must be made whether the Variable under the different Topic or Term also applies to the same data set.
• If more than one Term within a single Topic applies, multiple groups should be entered with the Topic repeated each time.
• If more than one Variable within a single Term applies, multiple groups should be entered with the Topic and Term repeated each time.
• If more than one Detailed Variable within a single Variable applies, multiple groups should be entered with the Topic, Term and Variable repeated each time.
• If the Variable designation is too specific, Topic and Term may be specified alone.
• Detailed Variables do not need to be selected from a list. There are no limitations on these words.
• The Parameter Valids are a generalization of the kinds of measurements found in data sets. The Parameter Valids guide users at search time from a broad terminology (Topics) to a terminology considered suitable for search purposes by most Earth scientists (Variable). Often however, data sets contain highly specialized terminology of the actual measurement value. The generalized terminology of the parameters is tied to the data set's highly specialized terminology by use of the Detailed Variable field. DIF writers are encouraged to populate the Detailed Variables with the specialized measurement terminology found in the data set itself. The user may be a specialist who will need to know the specialized terminology.
• New parameters may be suggested for inclusion in the list. When suggesting new valids for keyword searches, consider the user who will search with that word. A consistent level of specificity should be maintained among words in any single list. Before suggesting new parameters, review the Parameter Keyword Rules at http://gcmd.nasa.gov/valids/rules.html and the current parameter keyword list in Appendix A.

Examples

Group: Parameters
    Category: Earth Science
    Topic: Atmosphere
    Term: Precipitation
End_Group

Group: Parameters
    Category: Earth Science
    Topic: Biosphere
    Term: Aquatic Habitat
    Variable: Benthic Habitat
End_Group

Group: Parameters  
    Category: Earth Science
    Topic: Biosphere
    Term: Zoology
    Variable: Fish
    Detailed_Variable: Demersal Fish
End_Group

Group: Parameters
    Category: Earth Science
    Topic: Biosphere
    Term: Zoology
    Variable: Fish
    Detailed_Variable: Catch per Unit Effort
End_Group 

Group: Parameters  
    Category: Earth Science
    Topic: Human Dimensions
    Term: Environmental Effects
    Variable: Contaminants 
End_Group

Group: Parameters
    Category: Earth Science
    Topic: Hydrosphere
    Term: Water Quality
    Variable: Contaminants
End_Group