I've just published draft #2 of SRFI 153.  It was submitted
by John Cowan, author of the SRFI.

<https://srfi.schemers.org/srfi-153/>

Here are John's comments on the draft:

  Note that the title has changed, dropping the word
  "immutable"; you may have to change some metadata at the
  site.  The names iset and ibag have been changed to oset
  and obag, since the distinguishing mark is now orderedness
  rather than immutability.  Linear-update procedures have
  been added to match SRFI 113.

Here's the diff:

  <https://github.com/scheme-requests-for-implementation/srfi-153/compare/d68d7dba17419dcb424d0c76382c5829b998625b...4dff0ab528696d70ec084347108361bac80903de>

Regards,

SRFI Editor