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--- documentation:next_cdm:schema_revisions [2016/08/22 19:08] – frank_defalco
+++ documentation:next_cdm:schema_revisions [2018/02/12 20:23] (current) – [Proposal] patrick_ryan
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 ===== CDM Schema Revisions =====
+(needs rewriting to accommodate schemas in the specs)
   * Requesters: Frank DeFalco, Patrick Ryan
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   * The cohort, cohort_definition, cohort_attribute and attribute_definition tables move from the CDM specification to the results schema specification.
-  * The results schema specification will be managed by a database migration package that will be developed in a separate GitHub repository.
+  * The results schema specification will be managed by a database migration package that will be developed leveraging [[https://flywaydb.org/|Flyway]].
-  * The table in the OHDSI schema named cohort_definition be renamed as to avoid table name collision with the results schema specified cohort_definition table.
+  * The table in the OHDSI schema named cohort_definition and the result schema table 'cohort_definition' should not use the same name to avoid confusion.  Option 1: Rename 'cohort_definition' in the OHDSI schema.  Option 2: Rename 'cohort_definition' in the results schema.  Since 'cohort_definition' is being moved from CDM to results schema, it seems least disruptive to pursue Option 2.
 == Background ==
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 In April 2012 the [[http://75.101.131.161/download/loadfile.php?docname=CDM%20Specification%20V4.0|CDM V4 specification]] introduced the cohort table as a location to store records that share a particular feature during a particular time span and defined cohorts as a group of entities exposed to a common circumstance.  This table has since been included as part of the DDL statements to create a CDM database.
-When the initial tool to create cohort definitions ([[documentation:software:circe|CIRCE]]) was introduced it leveraged the existing cohort table that was found in the CDM schema as the location where it would store people identified when a cohort definition is executed against a CDM database resulting in a cohort of people.
+When the initial tool to create cohort definitions ([[documentation:software:circe|CIRCE]]) was introduced it introduced a new 'cohort' table that was found in the results schema where it would store people identified when a cohort definition is executed against a CDM database.
 Since that time many other tools have been created and new tables have appropriately been deployed in the separate results schema to store the data that they derive from the CDM schema.  This represents the fundamental issue we are seeking to resolve whereby some derived results are being stored in the CDM schema specified table and others are defined and maintained in the results schema.