Specification

Current version:

Specification v4.1 (PDF)

Older versions:

Specification v4.0 (PDF)

Specification v3.0 (PDF)

Specification v2.1 (PDF)

Specification v2.0 (PDF)

Specification v1.2 (PDF)

Specification v1.1 (PDF)

Specification v1.0 (PDF)