For context, here is the entire (older) Prior Publication Policy, from http://www.acm.org/tods/Authors.html#ManuscriptPreparation, as of July 2002.

"The technical contributions appearing in ACM journals are normally original papers which have not been published elsewhere. Widely disseminated conference proceedings and newsletters are a form of publication.

"A submission based on a paper appearing elsewhere must have major value-added extensions to the version that appears elsewhere. For conference papers, there is little scientific merit in simply sending the submitted version to a journal once the paper has been accepted for the conference. The authors learn little from this, and the scientific community gains little.

"The submitted manuscript should thoroughly consolidate the material, should extend it to be broader, and should more carefully cover related research. It should have at least 30% new material. The new material should be content material, not just the addition of proofs or a few more performance figures. This affords an opportunity to describe the novel approach in more depth, to consider the alternatives more comprehensively, and to delve into some of the issues listed in the other paper as future work."

From the discussion during summer 2002, there were several related but separable aspects.

• Whether there should be additional content in a TODS submission over a version that has already appeared elsewhere.

  The first two paragraphs of the policy makes clear the need for additional content.

• Who should decide whether the additional content is adequate.

  We agree with Peter's definition: "It should be left to the referees and editor (who will have the conference submission) to decide whether the journal submission fits the bill."

  Indeed, all questions of suitability for TODS ultimately come down to the handling editor, who makes the final decision.

• What should be considered additional content.

  There has been a lot of discussion on this. The consensus was that the following are examples that generally should be considered as additional content,

  • complex proofs of theorems that appeared in the original paper
  • non-obvious proofs of correctness of algorithms that appeared in the original paper
  • experimentation that enlarges the parameter space over which algorithm(s) are evaluated
  • an in-depth analysis of how the results can be applied in practice

  while the following, while perhaps helpful to understanding the paper, would generally not be considered as significant new content,

  • background context
  • obvious theorems
  • straightforward proofs of existing theorems
  • more discussion of related work
  • more discussion of the material for non-experts
  • a few more performance figures that don't significantly elucidate the applicability of the approach.

  Clearly "The new material should be content material, not just the addition of proofs or a few more performance figures." is misleading, since an insightful, well-executed proof is a contribution.

• Whether to be specific on how much new content is minimally required.

  Some have felt that it is best to leave this entirely up to the reviewers and editors, while others have felt that having a baseline is helpful.

• Should the TODS submission be a strict superset of the conference paper?

  This was raised by one person, indirectly. Elsewhere we push for shorter papers, but here we require journal papers to have more content than their associated conference paper, necessarily making them longer.

At the same time, the above characterization of what should be considered additional content is simultaneously too verbose and not specific enough. It doesn't seem possible to be adequately specific while also accommodating all the peculiarities of individual papers. So the preference is for a statement that gives some guidance without being too prescriptive.

Finally, the policy should explicitly address the superset issue. Papers should be allowed to reference the archival paper from which they were extended, rather than expecting them to include the entire paper as a subset.

The final wording, agreed to on July 23, 2002, is as follows.

"The submitted manuscript should have at least 30% new material. The new material should be content material, not just the addition of obvious proofs or a few more straightforward performance figures. The submitted manuscript affords an opportunity to describe the novel approach in more depth, to consider the alternatives more comprehensively, and to delve into some of the issues listed in the other paper as future work. At the same time, it is not required that the submitted manuscript contain all of the material from the published paper. To the contrary: only enough material need be included from the published paper to set the context and render the new material comprehensible."