You need a CD-ROM drive and a UNIX workstation with X11 and Fortran. Our disk includes source and many binaries for IBM RS-6000, Hewlett-Packard 700 series, Sun 4 (not Solaris 2), and DEC 3100.
In many branches of engineering and science there is a substantial computational element. Seismology is one of these. In taking up computational problems we should abandon books, journals, and reports and replace them with electronic documents that can be used to recreate any print document, including its figures, from its underlying data and computations. Today, few published results are reproducible in any practical sense. To verify them requires almost as much effort as it took to create them originally. After a time, authors are often unable to reproduce their own results!
It is time to plunge into a new era. These electronic documents contain everything needed to rebuild themselves; data, programs, graphics libraries, text, and word processor. This software, gathered and prepared at the Stanford Exploration Project, is presented in a way to encourage you to prepare reproducible electronic documents.
Some people see reproducibility of research as a troublesome ethical issue. We see it as an everpresent, irritating practical concern. We are annoyed when we cannot easily reproduce our own work. Some of us are irritated when other professors publish grandiloquent papers whose conclusions require too much time to confirm. And we are further frustrated when new students cannot reproduce (in a year) the work of other recently graduated students. Although each student prepares a doctoral dissertation that should enable others to reproduce that work, the reality is that paper documents are outdated; they no longer fulfill the role they did a generation ago when data consisted of photographs and pencil marks on a piece of paper---when theory was several pages of Greek symbols.
Paper no longer serves us well. Our data now resides in a computer, and our theory is embodied in computer programs. Many libraries overflow and they cannot afford the materials they want. At a million characters per book, over 600 books could be on a CD-ROM with a retail cost below 2 cents per book. We do not have 600 books so we filled our CD-ROM with the accumulated shared software library of many current and former students. We added many valuable, publicly available programs including fortran extenders and programs for composition and typesetting. We added seismograms. And, most importantly, we glued it together with "shell scripts" and "makefiles" that enable us and others to reproduce all our work. We call this a "living document."
Our experience shows that it is only slightly more difficult to give birth to a "living" document than a "dead" one. The major hurdles in preparing a doctoral dissertation, research monograph or textbook are these: (1) mastering the subject matter itself, (2) writing the ancillary technical programs, (3) using a text editor and word processing system, and (4) writing the command scripts that run the programs to make the illustrations. The difference between preparing a "live" document and a "dead" one, lies in the command scripts. Will they be run once and then forgotten, or will they be attached to the figure-caption pushbutton? Authors who wish to communicate will produce live documents. Authors who merely wish to advertise their scholarship without really sharing it will continue to produce dead ones. The increase in effort for the authors is minuscule---once they learn how to organize their work properly and to "file" it electronically.
When you look beneath the surface of these documents you will find everything you need to make your own living documents. And you can freely copy it from our disk. At the beginning of the computer revolution, I gave young students the advice: "Learn how to type." With the mass-storage revolution now underway, and with a $10 CD-ROM able to hold all the keystrokes you can type in a lifetime, I now advise everyone: "Learn how to file."
Jon F. Claerbout and Martin Karrenbach
Department of Geophysics