23.09d
There are four pipe delimited history files in this directory.

Cumulative_history_23.09d is a direct export of the concept history table as of Sep 25, 2023.  Subset_Cumulative_history_23.09d is a subset of the Cumulative_history that displays only cases where concepts have been created, merged, split, or retired.  These files are cumulative from the beginning of EVS recorded history to the given date.  All subsequent files are pulled on a monthly basis and are not cumulative.

Monthly_history_23.09d is a direct export of the concept history table from  Aug 38, 2023 to Sep 25, 2023.  Subset_Monthly_history_23.09d is a subset of the Monthly_history_23.09d that displays only cases where concepts have been created, merged, split, or retired.  These history files correspond to the Thesaurus_23.09d baseline.  History files for previous baselines can be found in the appropriate folder under archive.

***********************************************************
The fields in these files are conceptcode|editaction|editdate|referencecode

conceptcode is the unique, permanent, alphanumeric identifier of the concept

editaction is the activity being recorded (create, modify, split, merge, retire)

editdate is the date the activity occurred

referencecode is the identifier for a concept affected by or influencing the action, as detailed below

**********************************************************************************************

Reference codes are recorded in the following circumstances:

Merges - 
In a merge, two concepts are merged into one.  One of the two concepts survives and the other concept is retired.  
A merge history record is written for both of the concepts with a reference code of the surviving concept and a
retire record is written for the concept that retires.  In the case of C11111 merging with C22222 and C11111 surviving, the history 
will appear as follows:
C11111|merge|dd-mon-yy|C11111
C22222|merge|dd-mon-yy|C11111
C22222|retire|dd-mon-yy|(null)

Splits - 
In a split, a single concept is split into two.  The original concept survives and a new concept is generated.  Two 
split records are written for the original concept with reference codes for the resulting concepts and a create history
 record is written for the new concept. In the case of C11111 being split into C11111 and C22222 the history will appear as follows:
C22222|create|dd-mon-yy|(null)
C11111|split|dd-mon-yy|C22222
C11111|split|dd-mon-yy|C11111

Retires -
In a retirement the concept is moved from its old location in the tree hierarchy into the Retired_Kind.  A retire 
record is written for the retiring concept with a reference code of the old superconcept.  If a concept has multiple 
superconcepts, then a retire record is written for each reference.  In the case of retiring concept C11111 which has two 
superconcepts (C22222 and C33333), the history will appear as follows:
C11111|retire|dd-mon-yy|C22222
C11111|retire|dd-mon-yy|C33333