(Internal) What are Clump and Sieve Classes doing?

The ENVI Docs say nothing about how the Clump and Sieve Classes functions work.

Both Clump and Sieve classes use IDL's morphological operators, DILATE and ERODE in sequence. All kernal values are set to 1, but the kernel size is user selectable.

Sequences:

Clump = DILATE --> ERODE

Sieve = DILATE--> ERODE --> ERODE --> DILATE