This is the landing page for the Scala Improvement Process (SIP). The Scala Library Improvement Process (SLIP) has its own distinct mechanism documented at Scala SLIP github project page. In time, the SIP mechanism may be split out into a github oriented process similar to the SLIP mechanism.
The SIP process replaced the older SID (Scala Improvement Document) process, however the old completed SID documents are still available to review in the completed section of the SIP list.
For changes and additions to the Scala core libraries (i.e. those distributed with the main scala-lang download), a still rigorous (yet less demanding) process called the Scala Library Improvement Process (SLIP) exists.
SLIPs are intended for any library addition or modification that does not require associated changes to the Scala language or compiler.
Submitting a SLIP covers the process.
SIPs are for changes to the Scala language and/or compiler and are subject to a rigorous review process and are usually accompanied by changes to the Scala language specification, lots of review and discussion on the scala-internals mailing list and voting/approval milestones. Please read Submitting a SIP and our SIP tutorial for more information.