The Paper Reviewing Process

Learning how to review papers not only (obviously) makes you a better reviewer, but it can also help you as an author, since an understanding of the process can help you write your paper submissions for an audience of reviewers.  If you know the criteria that a reviewer will use to judge your paper, you are in a much better position to tailor your paper so that it has a higher chance of being accepted.

There are many good resources that describe the paper reviewing process already, including those that explain the process (and its imperfections) and those that provide instructions for writing a good review (as well as techniques to avoid).  There are also a few nice summaries of the review process for conferences in different areas of computer science that lend visibility into the process (e.g., here and here).  Program committee chairs sometimes provide guidelines for writing reviews, such as these.  I will not reiterate or summarize those previous articles here, but they are all definitely worth a read.  Instead, I will discuss the importance of the review process and how it differs from simply reading a paper; I’ll also talk about how to prepare (and ultimately write) a review.

I will not talk about the paper selection process (i.e., what determines whether a paper is ultimately accepted or rejected), but will instead focus on the creation of a paper review.  Program committee meetings are an important part of the paper selection process—at least in computer science—and I will be devoting a complete post to this topic next week.  Meanwhile, I recommend reading Matt Welsh’s post on the psychology of program committees.

The Review Process

Why understanding the review process is important. Whether you end up reviewing a lot of papers as a Ph.D. student, your research will definitely be subject to the paper review process.  It is imperative as a researcher to understand this process.  Knowing the process can help you better write your paper for an audience of reviewers (and a program committee), and it can also help you maintain perspective when your paper is accepted or rejected.  The process is far from perfect, and the outcome of the process is neither validation nor condemnation of your work.  How you react—and how you adapt your research or follow through on it after the acceptance (or rejection)—is far more important to long-term success.

In the “Introduction to the Ph.D.” class at Georgia Tech, I ask students to create a research idea and write it up; a subsequent set of assignments asks the students to review and evaluate the ideas as part of a “mock” program committee.  The process isn’t exactly the same as the review process for a full paper, but it is a lightweight way to have students experience the process first-hand in a low-stakes setting, and see both sides of the process (submission and review) at the same time.  In next week’s blog post, I will discuss program committee meetings in general, as well as some observations from this year’s (and previous years’) in-class experiences with the mock PC.

Reviewing vs. reading.  There are some significant distinctions between reading papers vs. reviewing them.  When reading a paper for your own enrichment, your goal is to gather information as quickly as possible.  In this case, you are a scientist who seeks to understand the context and content of existing work, to (for example) better understand how your own research might fit into the bigger picture or learn about techniques that might apply to your own work.  The goal of reviewing is different.  A reviewer’s goal is to first and foremost determine the suitability of a paper for some conference and second, to provide feedback to the authors to help them improve the paper in subsequent revisions.  Remember that the reviewer’s primary goal trumps all other objectives: A reviewer often has a large number of papers to process and is typically not deeply devoted to improving the content of any particular paper.  If you are lucky, you will get a diligent, thoughtful reviewer who provides thorough feedback, but do not be surprised if a review is not as thorough as you would have liked, or if the review “misses” some point you were trying to make.  We would all like reviewers to make three passes through your paper submission—and, these are the instructions I would give, too, in an ideal world.  Unfortunately, however, you will be lucky in many cases to get two thorough reads.  The reviewer’s main goal is to determine the paper’s suitability for publication.  As an author, you shouldn’t be surprised if some of the comments seem trivial: there may be underlying issues of taste that drove the reviewer’s opinion on your paper that a reviewer may not explicitly state.  Whenever I read reviews I receive for a rejected paper, I try to look past specific detailed quibbles (or “excuses” for rejecting the paper) and figure out the big picture:  the reviewer couldn’t find a reason to accept the paper.

Calibration: Reviewing one paper vs. reviewing many papers. The paper review process can differ depending on who, exactly, is reviewing the paper.  For example, as a Ph.D. student, you may review one or two papers at a time, as an “external reviewer” for a conference or journal.  Journal editors and program committee chairs often seek the help of external reviewers if they need a particular subject-matter expert to review a paper.  Later in your Ph.D. career, you may have established yourself as an expert on a particular topic and find yourself reviewing a paper here and there on a handful of topics.  Sometimes a member of the program committee (e.g., your advisor) might ask you to help review a particular paper.  As you progress in your career, you will be asked to serve on program committees yourself, whereupon you’ll find yourself with tens of papers to review over the course of a couple of months.  Ironically, it is sometimes easier to review a group of papers than a single (or a few) papers, because seeing a group of papers helps you “calibrate” your scores and rankings of papers according to the general quality of papers that have been submitted to the conference.    If you have been asked to review a single paper for a conference, you should either figure out how to calibrate your assessment with respect to other papers that might have been submitted, or simply review the paper on its merits while reserving judgement as to the paper’s ultimate disposition.

Does the Paper Realize a Great Idea?

Look for a reason to accept the paper.  Does it realize a great contribution or idea?  Every paper is imperfect.  The paper may have made an incorrect or imperfect assumption.  The experiments may not have been as thorough as you liked.  The graphs may be difficult to read.  Parts of the paper may be difficult to understand.  These types of issues certainly reflect problems with a paper, but they do not necessarily constitute a reason to reject a paper if they do not affect the correctness or significance of the main underlying conclusion or contribution of the paper.  Therefore, the first two questions I ask myself when reviewing a paper are: (1) Does the paper have a great idea?; and (2) Does it realize the great idea?  (or, alternatively, to what extent does it realize that great idea, since typically no paper is water-tight).

What makes an idea “great”?  Judging a paper’s contribution turns out to be highly subjective, which is why the review process remains so uncertain.  A paper isn’t judged on a set of fixed checkboxes, a grading “key”, or any notion of absolute correctness.  Reviewers often reserve considerable judgment based on “taste“, and reasonable people will disagree as to the merits of the main contribution or idea in a paper.  In fact, there has been a fair amount of documentation that, as reviewers, we are often quite terrible at predicting the merits of a particular piece of submitted work:  There’s a great article on this topic, as well as some parodies to illustrate the subjective nature of the process.  Many fields have also introduced a “test of time” award to papers from past decades, to recognize accepted papers that have truly had long-term positive impact (implicitly acknowledging that this is almost impossible to assess when a paper is first published).  Due to the subjective nature of this judgment, it is all the more important that your writing is clear, and well-matched to what a reviewer is looking for (i.e., the contributions and ideas).

Invariant questions.  Different conferences may have different value structures, and the chairs of any given conference may ask the reviewers to focus on different criteria when judging a paper.  Regardless, there are some invariant questions that most reviewers would (or at least should) always consider, including:

  • Is the problem important?  What problem is the paper trying to solve, and is it important?  Seek to summarize the paper’s contribution in one sentence.  Make this short summary the beginning of your review, as well.  Try to convince yourself (by reading the paper or otherwise) that a solution to the problem that the paper is proposing would advance knowledge or significantly improve the state of affairs for some group of people.  Note that you may not care about the problem, but also ask yourself whether you can imagine some group of readers who will be interested in the solution to the problem. When asking yourself this question about a paper, try to divorce your own taste about the problem’s importance from the more general question concerning whether there is some group of people who would be interested in the problem the paper is addressing and solving.
  • To what extent does the paper solve the problem it describes?  A single paper very rarely closes the book on a single problem, but it may take an important step towards solving the problem.  It might solve the problem for an important set of operating conditions or under a new set of assumptions.  Or, if the problem area is completely new, perhaps the paper doesn’t really solve the problem at all, but simply articulating a new problem area for follow-on work is a significant contribution.
  • What is the “intellectual nugget”?  As a reviewer, I try to identify whether a paper has a particular intellectual kernel that lies at the heart of the solution.  This kernel is often what separates an important research contribution from a simple matter of engineering.  This intellectual nugget might be the application (or invention) of a particular technique, a proof of correctness (where one previously did not exist), or an attempt to put the solution into a broader intellectual context.  In other words, the intellectual contribution might be to take a general problem and tackle a specific sub-problem (e.g., under certain assumptions or conditions), or to take a specific problem and generalize it (e.g., develop a general theory, proof of correctness, or taxonomy).  Looking through the paper for applications of specific research patterns can help identify an intellectual nugget, if one exists.
  • What is the main contribution or conclusion?  Is it important?  As a reviewer, I try to concisely articulate the paper’s main contribution (or small number of contributions).  Often, a paper will helpfully summarize those contributions somewhere in the introduction (Jim Kurose’s advice on writing paper introductions advises the writer to explicitly do so).   The reviewer’s job is then to assess whether those contributions are significant or important enough to warrant a publication.  The significance of those contributions often depends on the perceived increment over previous work.  All work is incremental to some degree, as everything builds on past work.  The author’s job is to convince the reviewer that the increment is important, and the reviewer’s job is to assess the author’s claims of significance.
  • Does the content support the conclusion?  An introduction may make broad (or wild) claims, and it is important to dig into the paper to determine whether the content of the paper supports the conclusion.  Are the experiments run correctly?  Are they based on the correct set of assumptions?  If the conclusion involves comparison to previous work, is the comparison performed in a controlled manner, using an equivalent (or at least fair) experimental setup?  If applicable, have the authors released their code and data so that you (or others) can check the claims yourself?

Preparing Your Review

Consider the audience.  Not every publication venue is the same.  Some venues are explicitly geared towards acceptance of early, incomplete work that is likely to generate discussion (many workshops use this criterion for acceptance).  Other venues favor contributions that constitute well-executed, smaller increments.  When reviewing a paper, either externally or as a member of a committee, your first question should be to consider the audience for the conference, workshop, or journal, and whether the likely audience for the venue would benefit from reading the paper.  The question of audience involves that of both the “bar” for acceptance (Does the paper meet the audience’s standards for something that is worth reading?) and the “scope” of the venue (is the paper on-topic for the venue?).  Often, scope can be (and is) broadly construed, so the key question really boils down to whether the likely audience for the paper will benefit from reading it.

Consider the standards. Your standards will (and should) vary depending on the venue for which you are reviewing a paper submission.  Workshops are typically more permissive as far as accepting “vision” papers that outline a new problem or problem area or papers that “foster discussion” than conferences, which typically aim to accept more complete pieces of work.   Nevertheless, even the standards for a conference review process will vary depending on both the conference itself, the program committee chair’s instructions about how permissive to be, and the relative quality of the group of papers that you are reviewing.  A good way to get a sense for the standards of a conference for which you are reviewing is to read through the complete set of papers that you have been asked to review and rank them, before writing a single review.  This will ensure some level of calibration, although it is still biased based on the set of papers that you are reviewing.  Reading past proceedings of the particular journal or conference can also help you determine the appropriate standard to set for acceptance.

Consider the purpose.  Different papers serve different purposes.  Multiple paper submissions to the same venue might in fact have quite different purposes, and it is important to establish what the paper is contributing (or attempting to contribute) before passing judgement.  For example, a paper might be a complete piece of work, but it might also be a survey, a tutorial, or simply a proposal.  If the paper is one of the latter types, your first questions as a reviewer should concern whether the audience would benefit from the survey, tutorial, or proposal, and whether such a paper meets the standards for the conference.  If the answers to those questions are “yes”, then your evaluation should be tailored to the paper’s purpose.  If the paper is a survey, your assessment should be based on the completeness of the survey, with respect to the area that the paper is claiming to summarize.  If the paper is a tutorial, is the description correct and clearly described?  If the paper is a proposal, does the proposed research agenda make sense, and is the outcome (if the proposal is successful) worthwhile?

Consider the big picture.  Every paper can be rejected.  It is always easy to find reasons to reject a paper.  The reviewer’s goal should not be to identify the reasons to reject a paper, but rather to determine whether there are any reasons to accept the paper.  If the answer to that question is negative, then it is always easy to find “excuses” to reject a paper (recall the discussion above).  You should be aiming to figure out whether the paper has important contributions that the audience will benefit from knowing about, and whether the paper supports those contributions and conclusions to the level of standard that is commensurate with the standard of the audience and the venue.  One litmus test I use to ensure that a negative aspect of a paper does not condemn it is to ask myself whether the problem (1) affects the main conclusion or contribution of the paper; and (2) can be fixed easily in a revision.  If the problem doesn’t affect the main contribution or conclusion, and if it can be easily fixed, then it should not negatively affect a paper’s review.

Writing Your Review

Start with a summary of the paper and its contributions.  A short, one-paragraph summary describing the paper’s main contribution(s) demonstrates to the authors (and to you!) that you understand the main point of the paper.  This helps you as a reviewer articulate the main contributions and conclusions of the paper for the purposes of your own evaluation.  Try to address the type of paper it is (is it a survey paper, for example?), the context for the paper (i.e., how it builds on or relates to previous work), its overall correctness, and its contributions.  If you cannot concisely summarize the paper, then the paper is not in good shape, and you can reflect this assessment in the review, as well.  These summaries are very helpful to authors, since they may not match the authors’ views of the main contribution!  For example, as an author, you can easily figure out if you’ve “missed the mark” or whether the reviewer fundamentally misunderstood the paper by reading a reviewer’s summary of your own work.  If the summary of the contribution does not match your own view of the paper’s contribution, then you know that you have some work to do in writing and presentation.

Assess whether the paper delivers on the main claims and contributions.  You should provide an assessment, for each of the paper’s main claims and contributions, whether it delivers on that claim.  If the main contribution of the paper is flawed, you should indicate whether you think a flaw is “fatal”, or whether the authors could simply fix the flaw in a revision if the paper is accepted.  Sometimes flaws (e.g., inconsistent terminology) are fixable. Other flaws (e.g., a questionable experimental setup) may or may not be fixable.  While it might seem that a broken experimental setup is “fatal”, ask yourself as a reviewer whether the conclusions from the paper’s experiments as is are still meaningful, even if the authors have not interpreted the results correctly.  If the conclusions from the experiments can be restated and still turn out to be meaningful contributions—or, if the flaw in an experiment doesn’t affect the main contribution or conclusion—then even a flaw in experiments can likely be fixed in revision.  Occasionally, however, experiments may need to be completely redesigned because they don’t support any meaningful conclusion.  Or, the content of the paper may simply be incorrect; sometimes correctness issues are difficult for a reviewer to spot, so a paper isn’t necessarily “correct” simply because a reviewer has validated the paper.  Regardless, if there are correctness issues that affect the main contribution of the paper that call into question whether the main result or contribution is correct in the first place, the paper’s review should reflect these concerns and likely cannot be accepted.

Discuss positive aspects of the paper; always try to find something positive, even in “bad” papers.  It is easy to identify problems with a paper.  It can be much trickier (especially with “average” papers) to identify the positive aspects and contributions, but most papers typically have at least some small kernel of goodness.  Even for particularly bad papers, there might be one sentence in the introduction, discussion, or future work section that makes an interesting point or highlights a possibility for interesting contributions.  In a pinch, if you can’t find anything positive, those are good places to look.  As a reviewer, you can remark that those observations are interesting, and that you would really like to see those parts of the work further developed.  These positive comments aren’t just for author morale (although that’s important, too): They give the author a direction to move forward.  The worst reviews are those that reject a paper but don’t provide any specific action for moving forward.  The best reviews are those that highlight the positive aspects of the work, while identifying weaknesses and areas where the work could be further developed to address weaknesses or build on the paper’s existing strengths.

Criticize the paper, not the authors.  When writing your review, consider the type of review that you would like to receive.  Always be polite, respectful, and positive.  Don’t be personal.  Choose your language carefully, as it will help convey your message.  For example, if you say “the authors don’t consider the related work”, that is a much more personal statement than “the paper doesn’t consider the related work”.  (In fact, you don’t know if the authors considered a particular piece of related work anyway; they may have simply chosen not to include it in the writeup!)  Talking about “the authors” gets personal, and it will put the authors themselves on the defensive when reading your review.  Instead, focus on “the paper” and frame your critique around “suggestions for improvement”.  Never, ever insult the authors; don’t accuse the authors of being sloppy or unethical researchers.  As a reviewer, you don’t always know the full context, so limit your judgement to what you can directly conclude by reading the paper.

Consider the type of feedback you would like to receive.  Receiving reviews for rejected papers is a part of the research process, but it is never fun for the authors (particularly new Ph.D. students). Do your part to contribute positively to the process by suggesting changes that you’d like to see if you had to review the paper again.  In all likelihood, you may see the paper again in the form of a revision!

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