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Catalogues are always flat views although they can be built from multiple relational data tables underneath.

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CatalogueItem

A 'virtual' column that is made available to researchers. Each Catalogue has 1 or more CatalogueItems, these store the columns description as well as any outstanding/resolved issues.

CatalogueItems can be tied to the underlying database via ExtractionInformation . This means that you can have multiple extraction transforms from the same underlying ColumnInfo e.g. PatientDateOfBirth / PatientYearOfBirth (each with different governance categories).

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CohortAggregateContainer

Cohort identification is achieved by identifying Sets of patients and performing set operations on them e.g. you might identify "all patients who have been prescribed Diazepam" and then EXCEPT "patients who have been prescribed Diazepam before 2000". This is gives you DISTINCT patients who were FIRST prescribed Diazepam AFTER 2000.

A CohortAggregateContainer is a collection of sets (and subcontainers) which are all combined with the given SetOperation (UNION,INTERSECT or EXCEPT)

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CohortIdentificationConfiguration

Describes a configuration for identifying patients fitting a given study criteria. E.g. "I want all patients who have been prescribed Diazepam for the first time after 2000 and who are still alive today".

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