By default, Fluid Topics assigns the same value for the ft:clusterId metadata key to all the variants of a given document uploaded through the same source. Fluid Topics automatically assigns this value to content uploaded through an Author-it, DITA, FTML, Unstructured Document, or custom source if the ft:clusterId metadata element is implemented.
When using the default value, there is no need to declare the ft:clusterId metadata element in the Search page administration interface.
However, it is possible to cluster documents or topics from different sources together by manually overriding the default value that Fluid Topics assigns to the the clusterId metadata key.
The ft:clusterId metadata element is case-sensitive. If case does not match, the cluster will not work.