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FUNNELWEB MANUAL WEB PAGE
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Copyright (c) Ross N. Williams 1992,1999. All rights reserved.
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Permission is granted to redistribute and use this manual in
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any medium, with or without modification, provided that all
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notices (including, without limitation, the copyright
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notice, this permission notice, any record of modification,
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and all legal notices) are preserved on all copies, that all
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modifications are clearly marked, and that modified versions
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are not represented as the original version unless all the
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modifications since the manual's original release by Ross N.
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Williams (www.ross.net) consist of translations or other
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transformations that alter only the manual's form, not its
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content. THIS MANUAL IS PROVIDED "AS IS" AND WITHOUT ANY
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EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
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LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND
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FITNESS FOR A PARTICULAR PURPOSE. TO THE EXTENT PERMITTED BY
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LAW THERE IS ABSOLUTELY NO WARRANTY.
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<TITLE>4.1 The Danger of Modifying Languages</TITLE>
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<A HREF="index.html"><FONT COLOR="#FFFFFF"><B>Developer</B></FONT></A><BR>
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<A HREF="compile.html"><FONT COLOR="#FFFFFF">1 Compile</FONT></A><BR>
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<A HREF="design.html"><FONT COLOR="#FFFFFF">2 Design</FONT></A><BR>
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<A HREF="implement.html"><FONT COLOR="#FFFFFF">3 Implement</FONT></A><BR>
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<A HREF="modify.html"><FONT COLOR="#FFFFFF">4 Modify</FONT></A><BR>
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<A HREF="misc.html"><FONT COLOR="#FFFFFF">5 Misc</FONT></A><BR>
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<A HREF="gpl.html"><FONT COLOR="#FFFFFF">6 Licence</FONT></A><BR>
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<A HREF="search.html"><FONT COLOR="#FFFFFF"><B>SEARCH</B></FONT></A><BR>
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<P><FONT SIZE="5">4.1 The Danger of Modifying Languages</FONT><BR>
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<P>FunnelWeb is a computer program that implements the
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semantics of the FunnelWeb language. As such, you should
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take great care when making changes to FunnelWeb that
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modify the syntax or semantics of its language:
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<P><BLOCKQUOTE><B>Removing
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features:</B> Removal of features
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(featurectomy) is extremely difficult once the legacy base
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is using the features. If a feature is removed, users will
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have to go through all their files and find
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a way to simulate the effect of the removed feature with
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other features. This is usually unthinkable.</BLOCKQUOTE>
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<P><BLOCKQUOTE><B>Modifying
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features:</B> Modification of
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features has less direct impact than the removal of
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features, but can cause more subtle errors. Anyone modifying
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features should be sure that they
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are not inadvertently laying semantic traps.</BLOCKQUOTE>
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<P><BLOCKQUOTE><B>Adding
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features:</B> Although the addition
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of features is generally the most painless for the user
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community, as Hoare points out, it is also the most
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dangerous in the long run.</BLOCKQUOTE>
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<BLOCKQUOTE> "When any new language
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design project is nearing completion, there is always a mad
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rush to get new features added before standardization. The
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rush is mad indeed, because it leads into a trap from which
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there is no escape. A feature which is omitted can always be
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added later, when its design and its implications are well
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understood. A feature which is included before it is fully
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understood can never be removed later."<STRONG>[Hoare80]</STRONG>
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<P>The benefits of tight control over a language are
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<P><BLOCKQUOTE><B>Universal portability:</B> Source files can be
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treated as portable.</BLOCKQUOTE>
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<P><BLOCKQUOTE><B>Clear semantics:</B> Doubt about the semantics
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of the language are minimized.</BLOCKQUOTE>
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<P>For these reasons, I have decided to keep tight control
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over the FunnelWeb syntax and semantics. If you develop
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a variant of FunnelWeb, please take these issues into account.
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<A HREF="copyright.html">Copyright © Ross N. Williams 1992,1999. All rights reserved.</A><BR>
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