Collada is an xml-based file format which supports interoperability. 3D application users can exchange geometry, shaders and effects, physics, animation, kinematics.
Users can change multiple version representations of the same asset too. It is managed by the nonprofit technology consortium, the Khronos Group,
and has been adopted by ISO as a publicly available specification, ISO/PAS 17506. The schema and specification are freely available from the Khronos Group.
COLLADA documents that describe digital assets are XML files, usually identified with a .dae
(digital asset exchange) filename extension.
In March 2011, Khronos released Conformance Test Suite (CTS). The suite allows applications, that import and export COLLADA, to test against a large suite of examples, ensuring that they conform properly to the specification.
Sources: wikipedia and collada.org