From Kolab Wiki

Overview

In order to have a storage format which allows us to model all needed properties for all supported types, the Kolab XML Format was rebased on the existing xCal/xCard standards. To ease client implementation and to improve interoperability libkolabxml is developed, which servers as a serialization/de-serialization library. This library can be used from several languages through bindings.

Format Features

• Based on official standards:
• Todos/Events/Journals are fully xCal compliant
• Contacts/Distributionlists are fully xCard compliant
• Can model everything which is used in the Kolab XML Format 2.0, Kontact and Roundcube.
• Easily extensible
• Canonical storage format
• Supports Todos/Events/Journals/Contacts/Distribution Lists/Notes/Configurations

libkolabxml Features

• Few dependencies: Boost, xerces-c
• Efficient impelmentation
• Structural validation of XML-Documents through XML-Schema
• Language bindings for PHP and Python
• API matching the Kolab Format specification (respectively the used xCal/xCard specifications)