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This prospect raises the need to standardise inputs as much as possible and to guard against errors. One method, which can be used wherever the range of possible inputs is limited, is to supply the values for all alternatives. So, for instance, instead of inviting users to type in the text for (say) “New South Wales” (ie. g. 3). g. ”). 4 Processing scripts and tools The most basic operation on a server is to return a document to the user. However, many server operations need to include some form of processing as well.

For example, online processing of satellite images have been trialed but are not generally available because they tend to require a great deal of computation. The following examples give some idea of the sorts of interactive functions that can be, and are, online. 1 Environment Australia’s species mapper Environment Australia’s service Species Mapper (ERIN 1995) provided a system for querying its database of species distributions and plotting them on maps. However, the service went further than that.

If the user provides the boundaries from (say) a form, then we could generate a new script by using a Perl script to replace the variables in the template with the new values. Here’s a simple example of a Perl script that does this. # ! /usr/bin/perl # Build a simple script from a template # The associative array markup contains replacement values getvars fromform; filtertemplate; sub filtertemplate { while ($sourceline=) { chop ($sourceline) ; $targetline=$sourceline ; # Enter the input string into the template fields for ($i=0; $i<$no_of_tags; $i++) { $work=$tag[$i] ; $targetline =~ s/$work/$ formvar{$work}/gi; } print “$targetline\n”; } } This script acts as a filter.