The 
holds one 
per row. Each is of a particular type, and has a source 
and a destination 
An example of a is given below: 
where:
Only one record with the same id field will be current at any point in time. The current record will be the one with the most recent effectiveTime before or equal to the point in time under
If the 
field of this record is false ('0'), then the is 
at that point in time. If the field is true ('1'), then there is a between the 
identified by 
and 
.
The , , 
, 
, characteristicTypeIdand 
will not change between two rows with the same id, in other words they are immutable. Where a change is required to one of these fields, then the current row will be de-activated (by appending a row with the same id and the field set to false) and a new row with a new id will be appended.
The field is used to group 
with the same field into one or more logical sets. A with a field value of '0' is considered not to be grouped. All with the same and non-zero are considered to be logically grouped.
The field will be an unsigned 
, and will not be limited to a single digit value. There is no guarantee that they will be assigned sequentially, and the values will not be unique across 
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