Hi Andreas,
Are you looking to do something equivalent to writing an ACL in EXOS (if / then / action)?
If yes, you can create an ACL on ExtremeWare. Depending on if you have an 'i' series (Summit 48si, Summit 7i, Alpine, ex) or 'e' series switch (Summit 200/300/400), the commands are a little different.
Below is a link to the ExtremeWare CLI Guide. Page 491 describes how to create an access list.
The guide shows how to create ACLs for 'e' and 'i' series switches.
http://extrcdn.extremenetworks.com/wp-content/uploads/2014/02/ExtremeWareCommandRef78.zip
Hope this helps.
Regards
Tony