About an old paper, victim of peer review and editor’s choice, and about these

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About an old paper,victim of peer review and editors choice,

and about these

Glauco Masotti

Preface

This document is two sided, or perhaps three sided. On one side I am presenting you a paper, which I wrote,that was submitted to CAD for publication, in December 1993. Regrettably, the paper was rejected instead,and no other attempts to publish this work were made later, thus, since then, it rested in a drawer of mine,before it come into my hands again, in recent times.

What I am proposing you, its thus material which have been seen hitherto only by a very limitednumber of persons. From my point of view its like a piece of jewelry lost for a long time under the sand,which come to light again. Well, this perhaps is not your opinion. From your point of view it may be relevantthe fact that, after almost 19 years, this material, most likely, doesnt represent anymore the state of the artin this topic. As I abandoned this field many years ago, I dont really know how much the technology have

evolved and in which direction, however, what I can tell you is that what is described in the paper workedquite well, and constituted a remarkable improvement, in terms of easiness of use and performances offered,over competitor commercial systems. Thus I think you could still find valuable content in it, which could alsobe applied in other contexts (e.g. in nonlinear optimization). In particular, certain general principles, which arehighlighted in the paper, should maintain their validity across time.

The second side, developed in this preface, is the main reason for this publication, and it is areflection, which I am asking also to you to do, on the process which brought to rejection of the paper, whichends up with the questions was that decision right?, is this really the best that we can do?, and do wereally need peer review and editors?.

There could be also a third side, as I said, which could be entitled my life rowing countercurrent, butthis most likely wont interest you, and thus it will not be developed here.

The paper, object of discussion here, presented a software module for the modeling of assemblies, in which

the various parts were positioned via the interactive, sequential specification of mating constraints. Thepaper describes the capabilities of the module, as well as the problems encountered in its development andthe solutions found.

It must be said that what is presented in the following pages is a greatly revised version of a previousdocument, which was submitted for publication to the same journal (CAD) in September 1993. The fate ofthis first version was determined by just two referees! One of them lamented that the paper was confusedand unclear, and questioned many parts of it. Some observations were reasonable, and contributed to makethe second revision clearer, but others made me think that he/she didnt understood much of what I wrote,perhaps really my fault, but a referee should make some efforts to understand the point of view of the author,isnt it?

The other referee observed that the author (me) didnt discuss the vast literature on part matinganddidnt explain how his work improves on it. I still think that this should come out also from an attentivereading of the first version, but probably I hadnt emphasized enough certain aspects, I must admit instead

that the first remark was justified, too little space was dedicated to a discussion of known, related works.He/she also complained that the algorithm was demonstrated only with simple examples. Also thisobservation, was reasonable and acceptable, and contributed to improve the second version. After all it wasnot my business to write papers, working for industry and not for academy, thus inexperience may haveaccounted for some ingenuity in preparing the first version.

However the referee continued observing that similar algorithms already appeared in the literature andthat Just using an off the shelf algorithm from Press does not count as publishable work. I cannot describewhat I felt reading this. A sensation of real anger, like when you are victim of a profound injustice!What!? Months of work, of studies and trials, several new ideas developed and thousands of lines of codeimplemented and I just used an off the shelf algorithm? If this, presumed expert in the field, and honoredpeer, made such an observation, it means that he did not go into the details of my work! And, in this case,the details are what makes the difference.

In fact, if its true that in the first version I omitted an adequate discussion of known approaches to the

problem, I think to have filled this lacuna in the second version, so that you can read what the state of the artwas. At that time, all known works on the subject reported applications to more or less simple examples,generally even simpler of those used by me in the first version, but none reported of a truly spatial (3D)

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kinematism, like the last example that you can see in the second version of the paper. This result waspossible also because an adequate set of mating constraints was used, several of them introduced for thefirst time.

In my paper I also made a clear distinction between one-objectand n-objects positioning problems, aswell as between committed and step-by-step approaches in defining the position of parts. These concepts,were not clearly defined in previous published works. The referees may have considered these distinctionsas irrelevant, but taking one approach or another, changes the user perspective a lot. Also the mathematical

problems to be solved change, as in the various cases we may have underconditioned or overconditionedproblems, however the algorithm described can solve both.Known works typically used linearized algorithms, none reported, as I did, a detailed study on

exploitation of at least second order terms, which instead is essential to guarantee convergence in allpossible cases. None of these papers discussed in detail the difficult cases which may arise in practice andhow to overcome these, providing in all cases the desired solutions. The use of second order terms or thecomputation of a direction of negative curvature to escape local maxima or saddle points, in this context, wasan original contribution, as well as the particular exploitation of a polynomial approximation for the objectfunction.

Moreover, none of the known papers emphasized (or just reported) the importance of transforming thespace of variables in a uniform domain, and of rescaling the equations to guarantee a uniform and balancedcontribution of each term to the objective function. Just this detail accounts for at least an order of magnitudein speed of convergence!

The algorithm which I described in the paper is peculiar also for other contrivances, which, altogethercontribute to the final result, e.g. the temporary relaxation of some constraints, to escape local minima, theuse of temporary attractor points (a newly introduced concept), to escape unwanted solutions, the use ofrandom perturbations to determine the residual degrees of freedom.

Saying that my algorithm was similar to those already published, IMHO is thus like saying that horsesare similar to dogs! (After all they both have four legs, isnt it?). I also must emphasize that, considering allthese aspects, saying that I just used an off the shelf algorithm from press, is absolutely scandalous! Likesaying that Mr. Sacher, in conceiving and crafting his famous cake, did nothing more than just taking theingredients off the shelf!

Anyway, as I said, the two referees also made reasonable remarks, which were taken into account forpreparing the 2nd version of the paper, which I carried out with the support of my head of division. Thissecond version resulted in practice in a quite different paper. The text size doubled, stepping from 11 to 22

pages, an adequate discussion of known approaches was provided, details of the algorithm were explainedfurther, recurring to more complicated and meaningful examples, illustrated by a completely different set offigures. A final demonstration of the capabilities of the software module was shown, with the realization andsubsequent animation of a spatial kinematism.

It is so that, in December 1993, we submitted the new paper for reconsideration of publication. But allour efforts resulted vain. This time in fact it was the Editor who directly rejected the paper, without submittingit to a new process of evaluation! He justified this decision saying that he couldn't reconsider a rejectedpaper for publication after such a short time! Therefore he didn't take in any account the fact that the paperwas so much different from the previous one, and also the fact that we were so quick in preparing the secondversion, was paradoxically valued negatively rather than positively! He also said that he had a long queue ofaccepted paper waiting for publication, and this certainly played against us. He also suggested sending thepaper to another journal, or retrying with CAD in about a year. My consternation, in reading these words wasgreat, and this was the sentiment also of people of my group.

For a private company, the interest in publishing some of its work, through one of its members, is ingaining visibility and recognition, CAD played a dominant role at that time, thus publishing elsewhere wouldhave not been the same. Moreover those were times of rapid developments in the field, thus the appeal ofthe paper one year later could have been much lower. Therefore, we end up not pursuing further ourattempts for publishing the work.

Despite the rebuff received by the community of experts, that piece of software proved in the field itsefficacy. It received constant appreciation from the users, who evaluated it more powerful and simpler to usethan corresponding modules of the competitors. It was used also to model very complex machinery (likediesel motors) and remained in service, almost unchanged, for several years.



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At this point, considering that it was not the first time that I had problems with peer review1, but also that I amin good company, with the people who had similar experiences 2, I think that it makes sense to ask ourselvesthe questions which I anticipated above: was that decision right?, is this really the best that we can do?,and do we really need peer review and editors?.

I leave to you the answer to the first question; the last two questions instead, deserve someconsiderations. What could be the alternatives to the usual process of submitting papers to peer review andeditors approval? And would these be better? The limits of the traditional approach have been highlighted by

several authors, and the debate on this issue is open since several years

2,3,4

. The two papers cited are bothworth reading, but I want in particular to explicitly cite the enlightening words by Horrobin:The history of many innovations, both in medicine and in other areas of endeavor, indicates that the

innovators are often erratic, unsystematic, and difficult to deal with. The quality controllers often regard thework as of poor quality and not worth publishing or noting.

Editors must be conscious that, despite public protestations to the contrary, many scientist-reviewersare against innovation unless it is their innovation. Innovation from others may be a threat because itdiminishes the importance of the scientist's own work.

I don't want to say that all of the considerations above apply to the paper which follows, but I think thatthey are valid in general and we should be aware of these flaws in the traditional process of paper selection.

Well, I do believe that with current technology we are in condition to bypass these procedure and thatthe benefits in doing so would surpass the inconveniences. In fact we have now available a virtually unlimited

space for storing publications. Passing papers through a process of selection makes sense if we have alimited space available, like for traditional journals or conferences, but if the space is unlimited?We also have sophisticated and efficient means for retrieving the contents which may interest us. Thus

the solution could be as simple as lets publish everything on the web, or at least everything which passessome minimal, formal criteria for acceptance.

This does not mean that papers will not be evaluated! Papers could receive votes, and thus beevaluated by a much larger public than a couple of referees, plus we can count the number of citations.Evaluation and critical comments from a wide public should also contribute, better than a couple of reviewerscan do, to revise and improve reports, but, most of all, in this way we can avoid the censorshipof peers oreditors! So that heterodox, perhaps too ahead of time, or controversial works will still have a chance forappearing.

This could be the main road to go. Websites like Scribd or arXiv are interesting experiments in thissense, but I think they are still not up to the task. I thus hope that there will be an evolution in the sense I

advocated, and that, sooner or later, one or more websites, with all the required functionality, will emerge,gaining wide acceptance in the scientific community.

Returning to the paper, which is presented in the following pages, I am posting the original master, digitizedvia a scanner, because the electronic version, which I was able to recover from my old Mac, would requireextensive editing of mathematical formulas to be restored properly. I only made one correction of a wrongword, plus I edited the figures, to enhance their visual representation, and I associated to each figure therelated caption, for your convenience.

The Editor of CAD, suggested me to change the title, in case of submission to another journal or to aconference, because Placing mating condition at work was not meaningful to him. Perhaps he was right,the title of the first version was Interactive assembly of parts by means of mating constraints, but, inchanging the title for the 2nd version, we intended to stress the fact that this was not an academic, theoreticalwork, but the description of a fully functional part, actually employed for production in industry. Perhaps

another title can be found, capturing better this meaning, but we had not occasion to think about it again.

1 Glauco Masotti, "Floating-Point Numbers with Error Estimates (revised)", Jan 2012,http://arxiv.org/abs/1201.5975

2 C. W. McCutchen, "Peer review: treacherous servant, disastrous master", TECHNOLOGY REVIEW, Oct.1991,http://www.technologyreview.com/magazine/magpdf.aspx?id=486

3Horrobin, D. F., The philosophical basis of peer review and the suppression of innovation, J. Amer. Med.

Assoc., 263(10), 1438-1441, 1990,

http://jama.jamanetwork.com/data/Journals/JAMA/9237/jama_263_10_024.pdf

4Peer-review (refereeing),http://www.iva.dk/bh/core concepts in lis/articles a-z/peer%C2%AD_review.htm

http://arxiv.org/abs/1201.5975http://www.technologyreview.com/magazine/magpdf.aspx?id=486http://www.technologyreview.com/magazine/magpdf.aspx?id=486http://jama.jamanetwork.com/data/Journals/JAMA/9237/jama_263_10_024.pdfhttp://www.iva.dk/bh/core%20concepts%20in%20lis/articles%20a-z/peer%C2%AD_review.htmhttp://www.iva.dk/bh/core%20concepts%20in%20lis/articles%20a-z/peer%C2%AD_review.htmhttp://www.iva.dk/bh/core%20concepts%20in%20lis/articles%20a-z/peer%C2%AD_review.htmhttp://www.technologyreview.com/magazine/magpdf.aspx?id=486http://arxiv.org/abs/1201.5975http://jama.jamanetwork.com/data/Journals/JAMA/9237/jama_263_10_024.pdf


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Figure 1.Assembled slider crank mechanism.

Figure 2. Parts in unassembled initial position.



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Figure 3. Assembled configuration after sequential positioning of parts (without inserting the pins),

before closing the kinematic loop.

Figure 4. A configuration which correspond to a local maximum of the objective function.



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Figure 5. Here a saddle point will be encountered.

Figure 6. This configuration will end up in a local minimum.



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Figure 7. An unwanted optimal solution.

Figure 8. Trying to flip the parts by means of a side-of constraint will trap the solver in this local minimum.



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Figure 9. Desired 4-bar mechanism configuration.

Figure 10. Intermediate configuration of the four bars during the assembly sequence.



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Figure 11. Collapsed solution upon imposition of the last fits constraint.

Figure 12. Flipping the configuration using an "attractor point".



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Figure 13. Examining residual possibility of motion of parts.



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Figure 15. Animating the crank slider mechanism, searching for maximum drive angle allowed.

Figure 16. A two-stage cardanic joint example.



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Figure 17. Changing the configuration parameters requires the simultaneous repositioning of seven objects.

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