Posted by arlene

Java Yet more sophisticated interactive designs are possible using Java (developed by Sun Microsystems Inc.), which is now widely available. There are various Java-enabled browsers, such as Netscape Navigator 2.0 and above, Sun’s own HotJava, Opera, and Microsoft Internet Explorer.

Java is an object-oriented programming language that permits animated graphics as well as all the rest of the features of a full programming language, but it does require a powerful client machine (at least a good Pentium or equivalent with more than 16Mb of memory and a 32-bit operating system). Java development requires rather more investment of effort than does development using one of the scripting languages, but it offers the researcher much greater power to produce sophisticated task presentation systems with interactive graphics.

Java applets (small applications or programs, embedded in HTML pages) are delivered across the Web as required, and (in theory at least) function identically on all platforms. While Sun has had problems ensuring that all licensees implemented Java entirely according to its reference specification, better compliance can be expected in the future. Much effort has been expended to ensure that Java programs cannot compromise the security of the client machine, for example by crashing, or by writing to local disk drives. It is therefore a good choice of platform on which to develop Web-based research studies that demand sophisticated graphics or interface options.

However, Java has one disadvantage that has limited its usefulness up to now: Java programs tend to be quite large, and so they are slow to download across the dialup modem links with which most users currently access the Net. This can be mitigated, to some extent, by writing small, reusable applets that can be stored in browser caches. This approach works well if you use an applet that can be embedded in several different web pages. An increasing range of small, special- purpose Java applets is becoming available; these can be embedded in web pages to provide special interface devices, such as sliders or other interactive graphical widgets, in addition to the limited range offered by HTML forms. The idea is to use applets as components of more complex page designs involving HTML and JavaScript, and some useful applets are available ‘off the shelf’ for use without any special Java programming knowledge. You can find a variety of applets online via the TUCOWS site (see below).

It is worth mentioning that current HTML and DHTML standards do not support vector (line) graphics, which can be very useful for some types of study. Imagine, for example, an experiment on perceptual illusions: while these could be presented as static bitmap images (for example, JPG or GIF files) in some paradigms, the ability to drag line drawings to the ‘correct’ perceptual size would obviously increase the range of possible experimental manipulations. If such facilities are required, some good lightweight drawing applets are available online free of charge, such as JAIMEAS (available from TUCOWS) which supports vector graphics, interactive animation using combinations of bitmaps and line graphics, and interactivity with JavaScript.

Recently a number of integrated design and presentation systems for experiments and surveys have become available, allowing researchers the ability to design and present tasks with minimal programming.

ActiveX ActiveX is a name for a proprietary Microsoft technology (available only in Internet Explorer) by means of which applets can be embedded in web pages, extending the range of graphical and interface options, so in some respects it is similar to Java. However, there are two main differences: first, ActiveX applets are not portable across different hardware platforms, so they will only work on Intel machines running Windows; and, second, they are not secure in the way that Java applets are. ActiveX applets, once started, can in principle do anything, reading or writing the hard disk, spreading viruses or misbehaving in many possible ways. As a software author, you may be quite confident that your applet won’t compromise the user’s security, but users may be unwilling to trust a technology that lacks built-in safeguards.

While ActiveX applets will run on most machines, simply because most machines are Intel-based, and run Windows and Internet Explorer, their inability to work on all platforms still limits their applicability. Java does not suffer from these problems, so many developers will prefer it.

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