====== Parameter instance ======

A parameter instance is a set of [[Parameter_entry|entries]] for a realization of a [[Parameter_definition|parameter definition]].

In order to distinguish different instances, an instance can be [[Tag|tagged]]. The [[Tag|tags]] can be used to search for a specific instance (for instance: “show me all instances tagged ‘Food’“), and are also used to link instances in the database with exported data in Excel or [[Ecolego|Ecolego]].

===== Instances and dependencies =====

Instances are related to [[Dependencies_(Parameter_database)|dependencies]], and can be used when the maximum number of dependencies (two) runs out. Dependencies are used to vectorise models, where instances are used to distinguish different objects, cases or models.

Instances are more generic than dependencies; A parameter //weight// kg could be used for many different types of objects or substances. Creating a dependency for the //type// of object (_bonemarrow_, //Arsenic//, //grandmother// etc.) would be inconvenient: better in this case to create multiple instances of the //weight// parameter and [[Tag|tag]] them //bonemarrow//, //Arsenic// or //grandmother//. Tags also have the advantage that you can assign as many as you want (_weight_: //male//, //czech republic//, //overweight//).

===== See also =====

  * [[Database_design|Database design]]
  * [[Glossary_(Parameter_database)|Glossary]]
  * [[Parameter_definition|Parameter definition]]
  * [[Tag|Tag]]
  * [[Parameter_entry|Parameter entry]]