Contrived acronym in computer science and web development: Captcha

The term “captcha” was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University to denote a webpage element that is designed to tell humans and robots automatically apart: Captcha stands for Completely Automated Public Turing test to tell Computers and Humans Apart [1]. A captcha image, consisting of randomly generated characters squiggling inside a rectangle, is often encountered as a required-to-do field within a submit form. Misrecognizing certain letters or symbols, a user may get the interrogation vibe when asked if she would mind to do it again (and again …). In a recent TechnoFile contribution, David Pogue highlights the functioning of captchas as efficiency barriers and suggests the following meaning: Computers Annoying People with Time-wasting Challenges that Howl for Alternatives [2].

In case you haven't found an alternative yet or are going to argue that captchas are nevertheless pretty good in capturing—or should I write captcharing—machines employed by misconducting humans, then some interesting websites and JavaScript code will be helpful. Client side as well as server side scripting has been explained and demonstrated  [3,4]. Further, dynamic generation of webpages that include forms with captcha images can be achieved with various programming languages such as PHP, ASP, JSP, Perl, Python and Ruby [5].

What about identifying and appreciating the honest human being, who is interacting with your site; instead of targeting potential spambots all the time? Ben Hunt discusses a promising approach [6]. Invisibility is not only the strategy of spammers and spies, but can be derived by user-friendly technology, implemented as a backstage wizard that lets humans submit, sign in and hack as long as they employ finger work. Open creativity instead of captchability!

References and resources to explore
[1] www.captcha.net and www.google.com/recaptcha/captcha.
[2] TechnoFiles by David Pogue: Time to Kill Off Captchas. How the bot-proofing of the Internet in bringing humans down. Sci. Am. March 2012, 306 (3), page 23 [www.scientificamerican.com/article.cfm?id=time-to-kill-off-captchas].
[3] Simple JavaScript CAPTCHA Generator: typicalwhiner.com/190/simple-javascript-captcha-generator/.
[4] Implementation of Captcha in JavaScript: www.codeproject.com/Articles/42842/Implementation-of-Captcha-in-Javascript.
[5] Free CAPTCHA-Service: captchas.net.
[6] Ben Hunt:  CAPTCHA Alternative? Try this Invisible Human Check for Web Form Validation [www.webdesignfromscratch.com/javascript/human-form-validation-check-trick].

Case sensitive URL distinction? Don't rely on it!

A Uniform Resource Locator (URL) should not be case sensitive. At least, the domain-name part of the URL string is not interpreted with respect to case sensitivity [1].  Of course, you can type a URL into the provided field of your browser anyway you want. The same applies to the href attribute in an anchor tag of your HTML page. But the server that is hosting the targeted website may interpret file paths differently, depending on the occurrence of upper- and lower-case letters in an otherwise identical character sequence [2]. Unless you know exactly the set-up and configuration (Apache/Linux or other hosting software) of the server you are trying to access, you do not want to rely on either a case or non-case sensitive interpretation of your query.

Obviously, the common concern is to locate a website by not caring for upper- or lower-case letter typing and by avoiding  to end up with a “404 Error File Not Found” page [3,4]. Here, I like to emphasize the “mirror problem:” let us assume the server presence of multiple files, whose names vary only by selective capitalization. This problem is not restricted to website location, but is a general issue of targeted search and annotation. For example, in fields such as chemistry, case-sensitive presentation can be critical to distinguish between different materials: the symbols/formulae Co and CO represent the chemical element cobalt and carbon monoxide; CsI and CSi represent  cesium iodide and silicon carbide. Within each pair, notations differ by case only. Two files, named Co.htm and CO.htm, may not correctly be addressed or resolved as separate files, when located in the same directory. Such ambiguities are avoided—although generating overhead—by employing a more distinctive naming scheme. In our ThermoML file repository for molecular-composition-based open access of thermodynamic data and chemical publication hyperlinks, we choose a host-independent system of file names. For cobalt and carbon monoxide the files happen to be Co_aaa.htm and CO_aax.htm, respectively. The x is making the difference.

Keywords: name disambiguation, formula disambiguation, file names, identifiers, web hosting, Windows, Linux, UNIX, case standardization 

References and more on URL case sensitivity
[1] Bin-Blog: www.bin-co.com/blog/2007/10/case-sensitivity-in-urls/.
[2] wiseGEEK: www.wisegeek.com/are-urls-case-sensitive.htm.
[3] Ted Kuik: Case Sensitive URLs. Does capitalization matter? [www.coolnotions.com/Articles/Article_02.htm].
[4] Case-Sensitive URL's: www.infocellar.com/networks/internet/URL-case-sensitive.htm.

HTML5 microdata markup validation

HTML5 introduces the microdata concept to web page design: HTML elements can semantically be annotated by using item attributes such as itemscope, itemtype and itemprop. Typically, I am using the W3C Markup Validation Service at validator.w3.org to test my HTML5 pages and have experienced good results in checking markup validity. The good news is the bad news: the W3C validator is rather strict and—unfortunately—is too picky when it comes to microdata. For example, it reports errors detected in the shown code snippet, although this code has correct HTML5 syntax.

The code example illustrates annotation of a short text about a chemical substance. This code employs microdata (property/value pairs) according to the vocabulary defined at www.axeleratio.com/voc/chemid. The W3C validator complains about the item attributes, declaring that their use is not allowed on the selected elements at this point. In contrast, the (X)HTML5 Validator at html5.validator.nu declares that this code is valid HTML5, after submitting a page containing this code snippet. The NU Markup Validation Service at qa-dev.w3.org:8888/html5 came up with the same result. The latter validator—according to the statement on its site—checks the markup validity like the current W3C validation service, but instead uses the backend of the Validator.nu engine, which provides non-DTD-based validation support for a number of markup languages. Currently, this latter service is a potentially unstable pilot version, provided for demonstration and testing purposes only.

Suggested sites for microdata digging: 
W3C: www.w3.org/TR/microdata/
Wikipedia: en.wikipedia.org/wiki/Microdata_%28HTML%29
Tutorials Point: www.tutorialspoint.com/html5/html5_microdata.htm
Google: support.google.com/webmasters/bin/answer.py?hl=en&answer=176035

Gale crater on Mars named after Australian banker and astronomer Walter Frederick Gale

The Gale crater on Mars was named in 1991 after Australian banker and astronomer Walter Frederick Gale (1865-1945) [1-3]. This 150-kilometer-wide hollow emerged as the front-runner for the landing site of NASA's Curiosity rover and finally was picked for the $2.5 billion rover mission, successfully launched at the end of November in 2011 [3-5].

The leaders of the Curiosity mission chose the Gale crater as landing spot, because it promises to be the scene for exciting studies of Martian sedimentary patterns by using rock-vaporizing lasers, gas chromatography, mass spectrometry and X-ray diffraction instruments for chemical analysis as well as high-resolution digital cameras from Malin Space Science Systems (MSSS)  [6]. Channels (probably carved by flowing water) in the crater wall and mid-crater mound have been found during previous orbit-based studies:  the mound in the center of the five-kilometer-deep impact crater contains layered materials including clay and other minerals [7].

Keywords: astronomy, planetary science, areography, Martian topography, geology, terminology.

References and more to explore
[1] Google Mars Lab: www.google.com/mars/.
[2] Harley Wood: Gale, Walter Frederick (1865-1945). Australian Dictionary of Biography [adb.anu.edu.au/biography/gale-walter-frederick-6269].
[3] Space News: NASA Picks Gale Crater for Mars Science Lab Landing. July 25, 2011 [www.spacenews.com/civil/110725-nasa-picks-gale-crater-msl.html].
[4] Nancy Atkinson: Gale crater reported front-runner for MSL landing site. June 24, 2011 [www.physorg.com/news/2011-06-gale-crater-front-runner-msl-site.html].
[5] James Holloway: Mars Curiosity Rover successfully launched. November 27, 2011 [http://www.gizmag.com/mars-curiosity-launch-nasa/20627/].
[6] Eric Hand: The Mars Observer. Nature, November 24, 2011, 479 (7374), pp. 460-463 [www.nature.com/news/mike-malin-the-mars-observer-1.9402].
[7] NASA Mars Science Laboratory > Gale Crater: mars.jpl.nasa.gov/msl/mission/timeline/prelaunch/landingsiteselection/galecrater2/.

Martian locality inside the Gusev Crater: Columbia Hills named to honor the crew of the space shuttle Columbia

The Columbia hills inside Crater Gusev on Mars are named to honor the crew of the space shuttle Columbia, which disintegrated over Texas after re-entry into Earth's atmosphere in February 2003 [1,2].

The Columbia Hills are a range of low hills inside Gusev Crater that were visited in 2004 by Mars rover Spirit, equipped with alpha particle X-ray spectrometer (APXS) as well as infrared and Mössbauer spectrometer [3]. With this technology on board, at least ten different types of rocks were identified at the Columbia site, which is exposing rock formations that are different and older than the lava-flooded surroundings of olevine-bearing basalts [1,4]: layered granular deposits were discovered in the Columbia Hills and have been interpreted to be volcanic ash and/or impact ejecta deposits that have been modified by aqueous fluids.

Keywords: astronomy, planetary science, areography, Martian topography, geology, space shuttle Columbia disaster, terminology.

References and more to explore
[1] Ulf von Rauchhaupt: Der Neunte Kontinent - Die wissenschaftliche Eroberung des Mars. Fischer Taschenbuch Verlag, Frankfurt am Main, November 2010; pages 181.
[2] Joseph Lorenzo Hall: Columbia and Challenger: organizational failure at NASA. Space Policy 2003, 19, pp. 239-247 [josephhall.org/papers/nasa.pdf].
[3] mindat.org > Columbia Hills, Gusev Crater, Aeolis quadrangle, Mars: www.mindat.org/loc-189893.html.
[4] R. E. Arvidson et al.: Overview of the Spirit Mars Exploration Rover Mission to Gusev Crater: Landing Site to Backstay Rock in the Columbia Hills. J. Geophys. Res. 2006, 111, E02S01 [si-pddr.si.edu/jspui/bitstream/10088/3547/1/200640.pdf].

Eberswalde Crater on Mars named after the City of Eberswalde in the German State of Brandenburg

The Eberswalde Crater on Mars is named after the German town with the same name (in accordance with the rules for planetary nomenclature of the International Astronomical Union), located about 50 km northeast of Berlin in the German Federal State (Bundesland) of  Brandenburg [1,2]. The 65-km-diameter crater (centered at 24.3°S, 33.5°W, just north of the Holden Crater) contains a distributary fan, which is supposed to be an ancient delta in which a river deposited sediments, now hardened to sandstone [3].  The delta structure is (so far) the most convincing sign that a Martian river once flowed into a standing body of water [4,5]: possible streambed features, which are now higher than the surrounding terrain due to sediment hardening and erosion resistance, are assumed to be remaining parts that formed when the Eberswalde streams carved new channels.   

The Eberswalde Crater and its interesting geology came into focus in 2003 during the Mars Global Surveyor exploration program [6]. Based on images taken during this remote expedition, Michael Malin and Kenneth Edgett of Malin Space Science Systems discovered the Eberswalde delta with a surface are of 115 km² [7].

Keywords: astronomy, planetary science, areography, Martian topography, impact crater, Margaritifer Terra, history, terminology.

References and more to explore
[1] Ulf von Rauchhaupt: Der Neunte Kontinent - Die wissenschaftliche Eroberung des Mars. Fischer Taschenbuch Verlag, Frankfurt am Main, November 2010; pages 174 and 175.
[2] Mahalo > Eberswalde (crater): www.mahalo.com/eberswalde-crater/.
[3] David Pratt: Life on Mars: from microbes to monuments. December 2011 [davidpratt.info/mars-life.htm].
[4]  NASA Mars Science Laboratory > Possible MSL Landing Site: Eberwalde Crater: hmars.jpl.nasa.gov/msl/mission/timeline/prelaunch/landingsiteselection/eberswalde2/.
[5] M. Pondrelli, A. P. Rossi, L. Marianangeli, E. Hauber, K. Gewinner, A. Baliva and S. di Lorenzo: Evolution and depositional environments of the Eberswalde fan delta, Mars. Icarus October 2008, 197 (2), pp. 429-451.
doi: 10.1016/j.icarus.2008.05.018.
[6] NASA Solar System Exploration > Mars Global Surveyor: solarsystem.nasa.gov/missions/profile.cfm?MCode=MGS.
[7] slashtheseats.com/rrpedia/Eberswalde_%28crater%29.

Valles Marineris, a Martian rift zone named to honor the scientific team of the Mariner 9 program

The Valles Marineris got their name in 1973 to honor the scientific team of the Mariner 9 program [1]. The term “Valles Marineris” is the latinized form of the phrase “Mariner Valleys.” “Valles” is the plural form of the Latin noun “vallis.” The plural form in “Valles Marineris” indicates that this vast Martian surface feature is a system of multiple valleys or canyons.

Valles Marineris was discovered in 1972 by the Mariner 9 spacecraft [3]: Its length matches the distance between New York City and Los Angeles. This valley system, commonly referred to as the Valles Marineris trough system, is located close to the Martian equator, where it trends east-west from longitude 40°W to 110°W with a depth reaching 10 km [4]. During NASA's Global Surveyor Mission, the deepest point was found by laser measurements within the valleys in the Coprates Chasma region [5,6]: Valles Marineris does not exhibit the typical features of a river bed or canyon formed by water flowing down from source to delta. A complete understanding of how the Valles Marineris system originated and evolved by combination of water flow, magmatic processes, tensional fracturing and/or other forces is still far away.  

Keywords: astronomy, planetary science, areography, Martian topography, Latin, vallis, valles, terminology.

References and more to explore
[1] Google Mars Lab: www.google.com/mars.
[2] Glossary of Latin Words > V: www.bible-history.com/latin/latin_v.html.
[3] Valles Marineris, a Martian Rift Zone: themis.asu.edu/feature/16.
[4] Géomorphologie > New insight on genetic links between outflows and chasmata on Valles Marineris plateau, Mars (January 2009): geomorphologie.revues.org/7485.
[5] ESA Mars Express > Coprates Chasma and Coprates Catena: www.esa.int/esaMI/Mars_Express/SEMIRE1DU8E_0.html.
[6] Ulf von Rauchhaupt: Der Neunte Kontinent - Die wissenschaftliche Eroberung des Mars. Fischer Taschenbuch Verlag, Frankfurt am Main, November 2010; pages 114 to 119.