What is a CEP?

CEP stands for Coopr Enhancement Proposal. A CEP is a design document providing information to the Coopr community, or describing a new feature for Coopr or its processes or environment. The CEP should provide a concise technical specification of the feature and a rationale for the feature.

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

Because the CEPs are maintained as text files in a versioned repository, their revision history is the historical record of the feature proposal [1].

CEP Types

There are three kinds of CEP:

1. A Standards Track CEP describes a new feature or implementation for Coopr packages.
2. An Informational CEP describes a Coopr design issue, or provides general guidelines or information to the Coopr community, but does not propose a new feature. Informational CEPs do not necessarily represent a Coopr community consensus or recommendation, so users and implementors are free to ignore Informational CEPs or follow their advice.
3. A Process CEP describes a process surrounding Coopr, or proposes a change to (or an event in) a process. Process CEPs are like Standards Track CEPs but apply to areas other than Coopr packages. They may propose an implementation, but not to Coopr's codebase; they often require community consensus; unlike Informational CEPs, they are more than recommendations, and users are typically not free to ignore them. Examples include procedures, guidelines, changes to the decision-making process, and changes to the tools or environment used in Coopr development. Any meta-CEP is also considered a Process CEP.

CEP Work Flow

The CEP process begins with a new idea for Coopr. The CEP editors assign CEP numbers and change their status. Please send all CEP-related email to <coopr-developers@googlegroups.com> with a subject starting with CEP.

It is highly recommended that a single CEP contain a single key proposal or new idea. Small enhancements or patches often do not need a CEP; a patch submission can be submitted as a Coopr ticket. A more focussed CEP will likely be more successful, and the CEP editor may reject CEP proposals that are not focused or too broad. If in doubt, split your CEP into several well-focussed ones.

Each CEP must have a champion -- someone who writes the CEP using the style and format described below, shepherds the discussions in the appropriate forums, and attempts to build community consensus around the idea. The CEP champion (a.k.a. Author) should first attempt to ascertain whether the idea is CEP-able. For example, discussing the CEP on the <coopr-developers@googlegroups.com> or <coopr-forum@googlegroups.com> can help evaluate whther the idea might be rejected due to issues that are well-known by Coopr developers.

The CEP editor that approves a CEP will assign it a CEP a number, label it as Standards Track, Informational, or Process, give it status "Draft", and create and check-in the initial draft of the CEP. The CEP editor will not unreasonably deny a CEP. Reasons for denying CEP status include duplication of effort, being technically unsound, not providing proper motivation or addressing backwards compatibility, or not in keeping with Coopr's design philosophy.

As updates are necessary, the CEP author can check in new versions if they have SVN commit permissions, or can email new CEP versions to the CEP editor for committing.

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

Once the authors have completed a CEP, they must inform the CEP editor that it is ready for review. CEPs are reviewed the Coopr project leader, and other individuals identified by the editor. The reviewers may accept or reject a CEP or send it back to the author(s) for revision. For a CEP to be accepted 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 core Coopr functionality unduly. Finally, a proposed enhancement must be match the design philosophy of Coopr, or provide a clear justification for why this design departure is acceptable.

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

A CEP 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.

CEPs can also be replaced by a different CEP, rendering the original obsolete. This is intended for Informational CEPs, where version 2 of an API can replace version 1.

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

What belongs in a successful CEP?

Each CEP should have the following parts:

1. Preamble -- RFC 822 style headers containing meta-data about the CEP, including the CEP 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. Copyright/public domain -- Each CEP must either be explicitly labelled as placed in the public domain (see this CEP as an example) or licensed under the Open Publication License [5].

4. Specification -- The technical specification should describe the syntax and semantics of any new language feature. The specification should be detailed enough to allow competing, interoperable implementations for any of the current Python platforms.

5. Motivation -- The motivation is critical for CEPs that want to change core Coopr functionality. It should clearly explain why existing Coopr functionality is inadequate to address the problem that the CEP solves. CEP submissions without sufficient motivation may be rejected outright.

6. 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 similar software packages (e.g. PuLP or AMPL).

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

7. Backwards Compatibility -- All CEPs that introduce backwards incompatibilities must include a section describing these incompatibilities and their severity. The CEP must explain how the author proposes to deal with these incompatibilities. CEP submissions without a sufficient backwards compatibility treatise may be rejected outright.

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

   The final implementation must include test code and documentation appropriate for either the Coopr reference manual.

CEP Formats and Templates

There are two CEP formats available to authors: plaintext and reStructuredText [6]. Both are UTF-8-encoded text files.

Plaintext CEPs are written with minimal structural markup that adheres to a rigid style. CEP 3 contains a instructions and a template [2] you can use to get started writing your plaintext CEP.

ReStructuredText [6] CEPs allow for rich markup that is still quite easy to read, but results in much better-looking and more functional HTML. CEP 3 contains instructions and a template [3] for reStructuredText CEPs.

There is a Python script that converts both styles of CEPs to HTML for viewing on the web [4]. Parsing and conversion of plaintext CEPs is self-contained within the script. reStructuredText CEPs are parsed and converted by Docutils [7] code called from the script.

CEP Header Preamble

Each CEP must begin with an RFC 822 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.

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

The Author header lists the names, and optionally the email addresses of all the authors/owners of the CEP. 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 CEPs will be obscured as a defense against spam harvesters.

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

The Type header specifies the type of CEP: Standards Track, Informational, or Process.

The format of a CEP is specified with a Content-Type header. The acceptable values are "text/plain" for plaintext CEPs (see CEP 3 [2]) and "text/x-rst" for reStructuredText CEPs (see CEP 3 [3]). Plaintext ("text/plain") is the default if no Content-Type header is present.

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

Standards Track CEPs must have a Coopr-Version header which indicates the version of Coopr that the feature will be released with. Informational and Process CEPs do not need a Coopr-Version header.

CEPs may have a Requires header, indicating the CEP numbers that this CEP depends on.

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

Auxiliary Files

CEPs may include auxiliary files such as diagrams. Such files must be named cep-XXXX-Y.ext, where "XXXX" is the CEP number, "Y" is a serial number (starting at 1), and "ext" is replaced by the actual file extension (e.g. "png").

Reporting CEP Bugs, or Submitting CEP Updates

How you report a bug, or submit a CEP update depends on several factors, such as the maturity of the CEP, the preferences of the CEP author, and the nature of your comments. For the early draft stages of the CEP, it is probably best to send your comments and changes directly to the CEP author. For more mature, or finished CEPs you may want to submit corrections as Coopr tickets so that your changes do not get lost. If the CEP author is a Coopr developer, assign the bug/patch to him, otherwise assign it to the CEP editor.

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

CEP authors who are also Coopr developers can update the CEPs themselves by using "svn commit" to commit their changes.

Transferring CEP Ownership

It occasionally becomes necessary to transfer ownership of CEPs to a new champion. In general, we would like to retain the original author as a co-author of the transferred CEP, but that is really up to the original author. For example, it may be necessary to to transfer ownership of a CEP when the original author no longer has the time or interest in updating it or following through with the CEP process.

If you are interested in assuming ownership of a CEP, send a message asking to take over, addressed to both the original author and the CEP editor. If the original author does not respond to email in a timely manner, the CEP editor will make a unilateral decision.

CEP Editor Responsibilities & Workflow

The role of the CEP editor is to manage the administrative and editorial part aspects of managing CEPs. Currently, the CEP editor also has the final say in the acceptance of CEPs. (Note: This differs from Python's model of using a benevalent dictator for life (BDFL), which is not the CEP editor. If the CEP editor responsibilities become significant, then we could envision this separate role within Coopr. But for now the CEP editor also serves as the Coopr BDFL.)

The CEP editor must subscribe to the <coopr-admin@googlegroups.org> list. All CEP-related correspondence should be sent (or CC'd) to <coopr-admin@googlegroups.com>. For each new CEP that comes in the editor does the following:

• Read the CEP to check if it is ready: sound and complete. The ideas must make technical sense, even if they don't seem likely to be accepted.
• The title should accurately describe the content.
• Edit the CEP for language (spelling, grammar, sentence structure, etc.), markup (for reST CEPs), code style (examples should match CEP 8 & 7).

If the CEP is not ready, the editor will send it back to the author for revision, with specific instructions.

Once the CEP is ready for the repository, the CEP editor will:

• Assign a CEP number

• List the CEP in CEP 0 (in two places: the categorized list, and the numeric list).

• Add the CEP to SVN.

  The command to check out and edit the repository is:

  svn checkout https://software.sandia.gov/svn/public/coopr/trunk/ceps
  

  In particular, the svn:eol-style property should be set to native and the svn:keywords property to Author Date Id Revision.

  Also, the 'make' command needs to be run to generate new CEP web pages, which need to be added to the repository.

• Send email back to the CEP author with next steps (post to coopr-forum and coopr-developers).

Updates to existing CEPs also come in to <coopr-admin@googlegroups.org>. Many CEP authors are not SVN committers yet, so we do the commits for them.

Many CEPs are written and maintained by developers with write access to the Coopr codebase. The CEP editor monitors Coopr checkins for CEP changes, and correct any structure, grammar, spelling, or markup mistakes.

References and Footnotes

Copyright

Copyright 2010 by Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.