Credits

The MEP concept is borrowed from Python's [1] PEPs [2]. Much of this document is adapted from PEP-0001 [3] by Barry A. Warsaw, Jeremy Hylton, and David Goodger, and from GLEP-0001 [4] by Grant Goodyear.

What is a MEP?

MEP stands for "Mozart Enhancement Proposal". A MEP is a design document providing information to the Mozart/Oz community, or describing a new feature for Mozart/Oz. The MEP should provide a concise technical specification of the feature and rationale for the feature.

We intend MEPs to be the primary mechanisms for proposing significant new features, for collecting community input on an issue, and for documenting the design decisions that have gone into Mozart/Oz. The MEP author is responsible for building consensus within the community and documenting dissenting opinions.

Because the MEPs are maintained as text files under CVS control, their revision history is the historical record of the feature proposal [5].

Kinds of MEPs

There are two kinds of MEPs. A Standards Track MEP describes a new feature or implementation for Mozart/Oz. An Informational MEP describes provides general guidelines or information to the Mozart/Oz community, but does not propose a new feature. Informational MEPs do not necessarily represent a Mozart/Oz community consensus or recommendation, so users and implementors are free to ignore Informational MEPs or follow their advice.

MEP Work Flow

The MEP editors assign MEP numbers and change their status. The current MEP editors are Denys Duchier and Kevin Glynn. Please send all MEP-related email to <mep@mozart-oz.org>

The MEP process begins with a new idea for Mozart/Oz. It is highly recommended that a single MEP contain a single key proposal or new idea. The more focussed the MEP, the more successful it tends to be. The MEP editors reserve the right to reject MEP proposals if they appear too unfocussed or too broad. If in doubt, split your MEP into several well-focussed ones.

Each MEP must have a champion -- someone who writes the MEP using the style and format described below, shepherds the discussions in the appropriate forums, and attempts to build community consensus around the idea. The MEP champion (a.k.a. Author) should first attempt to ascertain whether the idea is MEP-able. Small enhancements or patches often don't need a MEP and can be injected into the Mozart/Oz development work flow with an enhancement "bug" submitted to the Mozart/Oz bugzilla [8].

The MEP champion then emails the MEP editors <mep@mozart-oz.org> with a proposed title and a rough, but fleshed out, draft of the MEP. This draft must be written in MEP style as described below.

If the MEP editor accepts the MEP, he will assign the MEP a number, label it as Standards Track (a better name would be nice here -- suggestions?) or Informational, give it status "Draft", and create and check-in the initial draft of the MEP. The MEP editors will not unreasonably deny a MEP. Reasons for denying MEP status include duplication of effort, being technically unsound, not providing proper motivation or addressing backwards compatibility, or not in keeping with Mozart/Oz philosophy.

If a pre-MEP is rejected, the author may elect to take the pre-MEP to the hackers@mozart-oz.org mailing list to help flesh it out, gain feedback and consensus from the community at large, and improve the MEP for re-submission.

The author of the MEP is then responsible for posting the MEP to the hackers mailing list, and marshaling community support for it. As updates are necessary, the MEP author can check in new versions if they have CVS commit permissions, or can email new MEP versions to the MEP editors for committing.

Standards Track MEPs consist of two parts, a design document and a reference implementation. The MEP should be reviewed and accepted before a reference implementation is begun, unless a reference implementation will aid people in studying the MEP. Standards Track MEPs must include an implementation -- in the form of code, patch, or URL to same -- before it can be considered Final.

MEP authors are responsible for collecting community feedback on a MEP before submitting it for review. A MEP that has not been discussed on hackers@mozart-oz.org will not be accepted.

Once the authors have completed a MEP, they must inform the MEP editors that it is ready for review. MEPs are reviewed by the Mozart/Oz Board, who may approve or reject a MEP outright, or send it back to the author(s) for revision.

For a MEP to be approved it must meet certain minimum criteria. It must be a clear and complete description of the proposed enhancement. The enhancement must represent a net improvement. The proposed implementation, if applicable, must be solid and must not complicate the distribution unduly. Finally, a proposed enhancement must satisfy the philosophy of Mozart/Oz.

Once a MEP has been accepted, the reference implementation must be completed. When the reference implementation is complete and accepted, the status will be changed to "Final".

A MEP can also be assigned status "Deferred". The MEP author or editor can assign the MEP this status when no progress is being made on the MEP. Once a MEP is deferred, the MEP editor can re-assign it to draft status.

A MEP can also be "Rejected". Perhaps after all is said and done it was not a good idea. It is still important to have a record of this fact.

MEPs can also be replaced by a different MEP, rendering the original obsolete (where version 2 of a policy, for example, might replace version 1).

MEP work flow is as follows:

Draft -> Accepted -> Final -> Replaced
  ^
  +----> Rejected
  v
Deferred

Some Informational MEPs may also have a status of "Active" if they are never meant to be completed. E.g. MEP 1 (this MEP).

What belongs in a successful MEP?

Each MEP should have the following parts:

1. Preamble -- RFC 822 style headers containing meta-data about the MEP, including the MEP number, a short descriptive title (limited to a maximum of 44 characters), the names, and optionally the contact info for each author, etc.

2. Abstract -- a short (~200 word) description of the technical issue being addressed.

3. Motivation -- The motivation is critical for MEPs that want to modify Mozart/Oz functionality. It should clearly explain why the existing functionality or policy is inadequate to address the problem that the MEP solves. MEP submissions without sufficient motivation may be rejected outright.

4. Specification -- The technical specification should describe the specific areas of Mozart/Oz that would be touched by this MEP. If new functionality is being introduced, what packages will that functionality affect? If new policy, who will be affected?

5. Rationale -- The rationale fleshes out the specification by describing what motivated the design and why particular design decisions were made. It should describe alternate designs that were considered and related work, e.g. how the feature is supported in other distributions.

   The rationale should provide evidence of consensus within the community and discuss important objections or concerns raised during discussion.

6. Backwards Compatibility -- All MEPs must include a section describing any issues of backwards incompatibilities and their severity. The MEP must explain how the author proposes to deal with these incompatibilities. (Even if there are none, this section should be included to clearly state that fact.) MEP submissions without a sufficient backwards compatibility treatise may be rejected outright.

7. Reference Implementation -- The reference implementation must be completed before any MEP is given status "Final", but it need not be completed before the MEP is accepted. It is better to finish the specification and rationale first and reach consensus on it before writing code or significantly modifying ebuilds.

8. Copyright/public domain -- Each MEP must either be explicitly labelled as placed in the public domain (see this MEP as an example) or licensed under the Open Publication License [#OPL].

MEP Formating and Template

There are two MEP formats available to authors: plaintext and reStructuredText [10].

Plaintext MEPs are written in plain ASCII text, contain minimal structural markup, and should adhere to a rigid style. MEP 9 contains a boilerplate template [7] you can use to get started writing your plaintext MEP.

ReStructuredText MEPs allow for rich markup that is still quite easy to read, but results in much better-looking and more functional HTML. MEP 2 contains a boilerplate template [6] for use with reStructuredText MEPs.

MEP Header Preamble

Each MEP must begin with an RFC 2822 style header preamble. The headers must appear in the following order. Headers marked with "*" are optional and are described below. All other headers are required.

  MEP: <mep number>
  Title: <mep title>
  Version: <cvs version string>
  Last-Modified: <cvs date string>
  Author: <list of authors' real names and optionally, email addrs>
* Discussions-To: <email address>
  Status: <Draft | Active | Accepted | Deferred | Rejected |
           Final | Replaced>
  Type: <Informational | Standards Track>
* Content-Type: <text/plain | text/x-rst>
* Requires: <mep numbers>
  Created: <date created on, in dd-mmm-yyyy format>
  Post-History: <dates of postings to hackers>
* Replaces: <mep number>
* Replaced-By: <mep number>

The Author header lists the names, and optionally the email addresses of all the authors/owners of the MEP. The format of the Author header value must be

Random J. User <address@dom.ain>

if the email address is included, and just

Random J. User

if the address is not given.

If there are multiple authors, each should be on a separate line following RFC 2822 continuation line conventions. Note that personal email addresses in MEPs will be obscured as a defense against spam harvesters.

While a MEP is in private discussions (usually during the initial Draft phase), a Discussions-To header will indicate the mailing list or URL where the MEP is being discussed. No Discussions-To header is necessary if the MEP is being discussed privately with the author, or on the hackers mailing list. Note that email addresses in the Discussions-To header will not be obscured.

The Type header specifies the type of MEP: Informational or Standards Track.

The format of a MEP is specified with a Content-Type header, which should read "text/plain" for plaintext MEPs and "text/x-rst" for ReStructuredText MEPs.

The Created header records the date that the MEP was assigned a number, while Post-History is used to record the dates of when new versions of the MEP are posted to hackers. Both headers should be in dd-mmm-yyyy format, e.g. 14-Aug-2001.

MEPs may have a Requires header, indicating the MEP numbers that this MEP depends on.

MEPs may also have a Replaced-By header indicating that a MEP has been rendered obsolete by a later document; the value is the number of the MEP that replaces the current document. The newer MEP must have a Replaces header containing the number of the MEP that it rendered obsolete.

Reporting MEP Bugs, or Submitting MEP Updates

How you report a bug, or submit a MEP update depends on several factors, such as the maturity of the MEP, the preferences of the MEP author, and the nature of your comments. For the early draft stages of the MEP, it's probably best to send your comments and changes directly to the MEP author. For more mature, or finished MEPs you may want to submit corrections to the Mozart/Oz bugzilla [8] so that your changes don't get lost.

When in doubt about where to send your changes, please check first with the MEP author and/or MEP editors.

MEP authors who are also Mozart/Oz developers can update the MEPs themselves by using "cvs commit" to commit their changes.

Transferring MEP Ownership

It occasionally becomes necessary to transfer ownership of MEPs to a new champion. In general, we'd like to retain the original author as a co-author of the transferred MEP, but that's really up to the original author. A good reason to transfer ownership is because the original author no longer has the time or interest in updating it or following through with the MEP process, or has fallen off the face of the 'net (i.e. is unreachable or not responding to email). A bad reason to transfer ownership is because you don't agree with the direction of the MEP. We try to build consensus around a MEP, but if that's not possible, you can always submit a competing MEP.

If you are interested in assuming ownership of a MEP, send a message asking to take over, addressed to both the original author and the MEP editors <mep@mozart-oz.org>. If the original author doesn't respond to email in a timely manner, the MEP editors will make a unilateral decision (it's not like such decisions can't be reversed :).

References and Footnotes

Copyright

This document has been placed in the public domain.