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Lab 1.5 Exercises

1.5.1. Apply Traditional Hypertext Concepts to WWW Content

a) Demonstrate how a bidirectional link between two Web pages may be emulated using HTML. Hint: The “name” attribute of the anchor tag might be one way.

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A1:

Answer: The following example illustrates the use of a “quasi-bidirectional” hyperlink between two pages. Use of the “Go Forward” and “Go Back” links on the respective pages enable a reader to “toggle” between the same locations (using the anchor name attribute) on the two pages.

<HTML>
<HEAD>
<TITLE>Example of Bidirectional Link</TITLE>
</HEAD>
<BODY>
<H1>Example of Bidirectional Link</H1>
<A name= "Top" href="...End_2.html#Bottom">Go Forward</A>
</BODY>
</HTML>

<HTML>
<HEAD>
<TITLE>Example of Bidirectional Link</TITLE>
</HEAD>
<BODY>
<H1>Example of Bidirectional Link</H1>
<A name= "Bottom" href="...End_1.html#Top">Go Back</A>
</BODY>
</HTML>

b) How might you add “rich text” to a Web page?

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A2:

Answer: Using the “onmouseover” attribute to many HTML tags, you could provide a small popup or text in the status bar of the browser that provides addition information about the link.

1.5.2. Evaluate WWW as a Hypertext System

a) How might the problem of “broken links” on the WWW be addressed with today's technology?

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A1:

Answer: For links to pages internal to your Web server, any scripting language that can traverse the directory tree and can file contents could be used. Each file is checked for HREF tags and then a check is made to see if the file is still where it supposed to be.

Some scripting languages like Perl even provide the ability to directly connect to Web servers and can therefore be used to check connectivity. Pages on your Web site could be checked for external URLs using Perl, and then Perl would check the connectivity to that page. Commercial products such as LinkScan will do this for you.

There are also a number of commericial Web development products (i.e., Alliare Home Site, Netobjects Fusion) that have site management functionality.

In addition, numerous technologies are under development that address the problem of “broken links”—link management. Research the work currently being done with URNs (Universal Resource Names) and Persistent URLs (PURLs).The following URLs can provide useful resources:

URNs: http://www.w3.org/Addressing/URL/uri-spec.html

PURLs: http://purl.oclc.org/

b) Ted Nelson once told a Web conference, “Your future is my past.” The implication was that the features he described for his Xanadu system should be incorporated into the WWW. Research some of Xanadu's features (e.g., “transclusion”) and discuss how they might be a part of the next generation of WWW.

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A2:

Answer: The following URL provides an interesting overview of the Xanadu system: http://www.internetvalley.com/intvalxan.html


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