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Frames and Wirth's Rule

The main problem I found with frames was the need to duplicate
information into at least 3 separate files.

    Frames Initialisation and <NOFRAMES> document
    The Frame Index or Navigation Document
    The Frame Top level or welcome page

Other pages the frames document displays also may need two versions
one with navagation buttons for the non-frame users.

The problem here can be summed up with Wirth's Rule

  Wirth's Rule:     Never store data in more than one place,
              sooner or later you will update one and not the other.

To solve this problem I have used two techniques.

   1/ A single file which is filtered to produce the three framing
      documents.

      For Example:  
         Anthony's WWW Images  http://www.cit.gu.edu.au/~anthony/
           Download the library, or look at a mirror site to see the
     framing.  Uses a C Pre-Processor file.

      That is to say I created one file with CPP #if #else #endif
      inserted which allows me to generate the three top level files
      from one source.

      The CPP (M4) source file for Anthony's WWW Images is at
           http://www.cit.gu.edu.au/~anthony/icons/www/Images.m4

      I use CPP defines   DEFAULT   INDEX   TOP  to generate the
      appropriate frame file using the following commands
      (which is put in a shell script or makefile)

      =======8<--------
      # DEFAULT :-  generate framing and default NOFRAMEs document
      /usr/lib/cpp -undef -P -DDEFAULT Images.cpp | \
             sed '/^$/d' > Images.html

      # INDEX   :-  output the frame navigation document
      /usr/lib/cpp -undef -P -DINDEX   Images.cpp | \
             sed '/^$/d' > Images_Index.html

      # TOP     :-   generate the framed top level welcome page
      /usr/lib/cpp -undef -P -DTOP     Images.cpp | \
             sed '/^$/d' > Images_Top.html

      =======8<--------

      The `sed' command is used to strip extra blank lines that
      CPP leaves behind

   2/ With the advent of the new Extended SSI of the latest Apache
      Web Server release, you can now use the Extended Server Side
      Includes, if-else-endif  tags.

      What you do is create one file like the CPP version above
      but link to this symbolic links for the other framing documents
      required.  You then use the XSSI to test the filename of the
      document requested to include or not-include the required parts.

      EG: You only have one document, but the XSSI allows the server
      to output the appropriate sections required for your frames
      according to the requested filename.

      To include or not include navigation buttons in other framed pages
      is even easier and only needs SSI (no extension needed)

      What you do is put your navigation buttons in a separate document
      (which could be shared by all your framed pages :-)
      and include it in your framed page with...

         <!--#include file="nav_buttions.html_incl" -->

      If you call this page    "page.shtml"   you create a symbolic link
      called  "page.html"  pointing to the same document.

      If you link to   "page.html"   you will get a framed version
      which as the file is NOT "Shtml" will not have the navigation
      buttons included!   If you link to  "page.shtml"  SSI will be
      performed and the "nav_buttions.html_incl" file included.
      hey presto navigation buttons will appear.

Of course these days, people use SSG (Static Site Genertors) to do all this.

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