Preliminary status is the initial conception of a specification and are generated by Technical Committees (or by Working Groups under advisement from a Technical Committee). The chair of a Technical Committee can propose a specification for Preliminary status with the agreement of the Technical Committee membership.
A Preliminary specification is considered to be a draft that is under construction. As such, it is liable to undergo many revisions and changes and is therefore considered to be unstable and not suitable for implementation. All Preliminary specifications have an informal specification identifier that begins with ‘P’.