.OTLN File Extension
File TypeOpal Outline File
File format categories include Binary, Text, XML, and Zip. The format of this file type has not been determined.
What is an OTLN file?
Outline created by Opal, an outlining program for Mac OS X; creates hierarchical lists for organizing notes, projects, reports, ideas, etc.; Opal is the successor to Acta and has been completely rewritten for Mac OS X.
More information is available at the Opal Product Page.