The extensions it defines must also be compliant
with the SIP processes for extensions. The group cannot modify baseline
SIP behavior or define a new version of SIP for IM and presence. If the
group determines that any capabilities requiring an extension to SIP are
needed, the group will seek to define such extensions within the SIP
working group, and then use them here.
I think these two paragraphs overlap enough that the charter will have less
room for misunderstanding if we just delete the first of them.