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Issue No.01 - January/February (2006 vol.10)
pp: 3-5
Published by the IEEE Computer Society
ABSTRACT
The Greasemonkey Firefox extension could change the way people view Web pages. It lets users load and execute JavaScripts on Web pages, allowing them to manipulate the page?s content in certain ways.
The original commercial Web browsers seemed more oriented toward pleasing Web page creators than their consumers. I found the ability of scripts to take over browser processing, generate a desktop full of pop-up windows, and execute arbitrary code on my machine offensive. (I was particularly offended when Internet Explorer stymied my self-educational efforts by occasionally refusing to let me see a Web page's source. A Web page's source is clearly no deep secret — after all, it's revealed by a few lines of Java. I suspected a dark conspiracy between Microsoft and the page-creation establishment, but that limitation turned out to be a bug, provoked, among other things, by having an alias to the text viewer on the desktop.)
But in a funny sense, there was a dark conspiracy. Early on, it wasn't a foregone conclusion that the Web would take off; commercial organizations had to be convinced to put content out there. (That changed.) Browser creators weren't eager to put obstacles in Web page creators' paths. Holders of large quantities of intellectual property often have a more expansive interpretation of intellectual property rights than consumers do. (Or not, depending on which way they think they might make more money.) Browsers and the Internet exposed operating systems to environments that were far more malicious than their designers had anticipated, particularly those operating systems in which — how can I say this politely — a seemingly innocuous action like adding a link to an application can cause another application to misbehave in unexpected ways.
In any case, it's my computer and I don't understand why purveyors of Web pages get to control what I see. Actually, I do understand why — for the same reason that commercial television broadcasts include commercials: the ability to get attention for selling soap is the incentive for hiring production crews to make the show. I'd like to get rid of the Web page commercials in the same way that users of digital video recorders (DVRs) want to skip the commercials (I care about the content and not the soap). DVRs are a threat to the business model of television. If I want to control what my browser presents (and informs the sending Web site), well, the traditional answer has been simple: write my own browser. Although I think I could figure out how to do that, and as much as I enjoy the Web, that's probably a bit more effort than it's worth.
Greasemonkey
That could be changing. Greasemonkey is a Firefox extension that lets you load and execute JavaScripts on Web pages. That is, you can define JavaScripts and specify a pattern for pages that are to execute these scripts. Once loaded, these scripts can manipulate the page's content, to, for example, remove particular elements, rearrange the page, or insert additional HTML. You can build scripts that are specific to particular sites or generic to all sites.
Examples of what this technology generically enables include suppressing the advertisements on a page, altering links that redirect through a tracking site so that they go directly to the desired target, putting up comparative prices from other sites when shopping, changing fonts and formats to make text more comprehensible, restoring parts of the interface (for example, context menus and status bars) on sites that disable them, automatically reloading pages to prevent auto-logouts or to always display more current data, skipping the registration process demanded by some sites by using shared logins, suppressing offensive language, allowing mouse-free navigation, converting currencies by mousing over them, and removing wrapper frames. Site-specific actions include saving standard searches in GMail, presenting the prices at alternative booksellers on Amazon, redoing Google's entire interface, or presenting the "printer-friendly" (that is, ad-free) version of the New York Times.
Having It Your Way
So how can you bring this power to your desktop? Broadly, there are two ways: you can download scripts that someone else has written or write your own.
There are many directories full of Greasemonkey scripts. For example, the generic examples I mentioned come from http://dunck.us/collab/GreaseMonkeyUserScripts. I've tried various scripts I've found on the Internet, with mixed results — that is, many of them don't work. This can be expected, given that I haven't paid for this freeware, that it needs to run on a variety of hardware, operating systems, and browser versions, and that particular Web pages can be moving targets. However, most people have only a limited tolerance for things that don't work (except, perhaps, for that operating system mentioned earlier). Widespread acceptance requires widespread reliability.
Of course, we're engineers here, and we can roll our own scripts. I set out to learn how to do this. My starting point was Mark Pilgrim's "Dive Into Greasemonkey," a free, online book ( http://diveintogreasemonkey.org). Pilgrim has also recently published a conventional (that is, physical) book on Greasemonkey programming. 1 Greasemonkey relies on your ability to understand two key technologies: JavaScript and the structure of Web pages. JavaScript, despite the ugly semicolon and curly-brace syntax, is intellectually a descendant of Scheme and Self. It borrows from Scheme notions of interpretation, functions as objects (including closures), and a dynamic environment. It borrows from dynamic object languages such as Self and certain AI systems the idea of objects as dynamically extendable maps from names to values. Of course, part of the power and attraction of Lisp and its descendants comes from their fluid programming and debugging environments — something more difficult to achieve for Web pages, but for which rudimentary tools are appearing.
The rub with respect to effective programming is that these technologies are being applied to the Web page data object, an often messy structure that intermixes structural elements (headings, anchors, and lists) with a variety of presentation elements (not only directly with font and style commands, but also indirectly with style sheets). A Web page creator has many ways to encode the page's content. Scripts must often rely on pattern expressions in XML query (XPath) expressions, but pattern matching can be an easily disrupted technique. Web page formats evolve. Good Greasemonkey scripts need to consider all these possibilities — a computationally and intellectually intractable problem.
Scripting Scripts
Early technology adopters wrote their own HTML, but GUIs were necessary before every grandmother could have her own custom Web page. Now grandmothers can build Web pages without knowing of the syntax or even the existence of HTML. Skilled JavaScript programmers can build Greasemonkey scripts, but learning JavaScript, XPath, and Web page formatting details is too much for most. To be transformative, this technology needs to become more accessible.
One such initial effort is Platypus ( http://platypus.mozdev.org), which advertises itself as providing a graphical interface for creating Greasemonkey scripts. This is roughly on the level of keyboard macros — I'll watch what you do and repeat it for you next time. The fly in this ointment (as experienced keyboard macro writers know) is that it takes foresight and cleverness to write macros that don't stumble on minor variations of structure. That is, the macro that moves over a character on a numbered list to skip the "number" falters when the list suddenly turns up with 10 items.
Platypus is a good start, but much more effort (and creativity) is needed. Ideally, a user-capable Greasemonkey scripting environment needs to present Web pages in a conceptual model that is straightforward and easy for the user to understand, as opposed to one that's close to the textual metal of presented pages. This will likely blend elements of the watch-what-I-do macros with wizards that disambiguate possible interpretations of gestures ("When you said you didn't want to see this image, did you mean to suppress all images, just images that come from another site, just images from the site of this image, or just this particular image?") and provide a more sensible vocabulary of actions. It will not be able to demand that the user know a volume of function calls or field names, while nevertheless making a rich library of additional functionality easily accessible. Excel, to say something nice about a product from that large operating system company, is a fairly successful example of enabling such user programming — spreadsheets were the original transformative technology that enabled laypersons to define useful computations without having to train for the computational priesthood. The challenge for Web page manipulation is to make such manipulation Excel-transparent without the underlying data model being Excel-simple.
Conclusion
Will Greasemonkey transform the Web? Perhaps. Greasemonkey and DVRs both have the potential to distort the economic model underlying the way the technology is used. Television producers are fighting back against DVR technology on several fronts: politically, trying to make "transforming" a television show an illegal violation of copy- or some other fancied right; technologically, by trying to make the "to-be-skipped" commercials less obviously commercials; and semantically, by moving from a model in which the commercial is a separate entity to one in which the product endorsements are part of the text and visuals of the entertainment itself.
Faced with the Greasemonkey threat of removing the parts of Web pages that pay the bills, we can expect similar responses from Web page creators. We can certainly expect the usual political efforts, with the usual one-sided polemics about ethics. Technologically, we'll have more complex presentation mechanisms (for example, mixing the advertising with the context in executable form, or Web pages that check to see that they haven't been modified before they'll present their information), more useful advertising (the genius of Google is to present ads that are twice as likely to be clicked and correspondingly only half as annoying), frequent changes of Web page formats to catch naïve scripts, and more complex intermixing of desired information with the economically sustaining information.
We have seen a continuing arms race between malware writers and detectors and between Web page creators and search engine writers. If this technology moves beyond high-tech early adopters to actually impact the way the Web is used, we should expect a similar continuing escalation of more clever Web page hacks and more cleverly generated Web pages. I just can't tell whether that particular arms race will produce a détente or mutually assured destruction.

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