
==== NAME ====

Tie::FieldVals - an array tie for a file of enhanced Field:Value data


==== VERSION ====

This describes version 0.6202 of Tie::FieldVals.


==== DESCRIPTION ====

This is a Tie object to map the records in an enhanced Field:Value data file
into an array. Each file has multiple records, each record has its values
defined by a Field:Value pair, with the enhancements that (a) the Value part
can extend over more than one line (because the Field names are predefined)
and (b) Fields can have multiple values by repeating the Field:Value part
for a given field.

Because of its use of the Tie::File module, access to each record is
reasonably fast. The Tie::File module also ensures that (a) the whole file
doesn't have to be read into memory (b) record changes are written to the
file straight away (c) record changes don't require the whole file to be
rewritten, just the part of the file after the change.

The advantage of this setup is that one can have useful data files which are
plain text, human readable, human editable, and at the same time able to be
accessed faster than using XML (I know, I wrote a version of my reporting
software using XML data, and even the fastest XML parsers weren't as fast as
this setup, once there were a reasonable number of records). This also has
advantages over a simpler setup where values are given one per line with no
indication of what value belongs to what field; the problems with that is
that it is harder to fix corrupted data by hand, and it is harder to add new
fields, and one can't have multi-line data.

It is likewise better than a CSV (Comma-Separated Values) file, because
again, with a CSV file, the data is positional and therefore harder to fix
and harder to change, and again one can't have multi-line data.

This module is both better and worse than file-oriented databases like
DB_File and its variants and extensions (such as MLDBM). This module does
not require that each record have a unique key, and the fact that a DBM file
is binary makes it not only less correctable, but also less portable. On the
downside, this module isn't as fast.

Naturally, if one's data needs are more complex, it is probably better to
use a fully-fledged database; this is oriented towards those who don't wish
to have the overhead of setting up and maintaining a relational database
server, and wish to use something more straightforward.

This comes bundled with other support modules, such as the
Tie::FieldVals::Row module. The Tie::FieldVals::Select module is for
selecting and sorting a sub-set from a Tie::FieldVals array, and the
Tie::FieldVals::Join is a very simple method of joining two files on a
common field.

This distribution includes the fv2xml script, which converts a
Tie::FieldVals data file into an XML file, and xml2fv which converts an XML
file into a Tie::FieldVals data file.


==== REQUIRES ====

    Test::More

    Carp
    Tie::Array
    Tie::File
    Fcntl
    Data::Dumper

    Getopt::Long
    Pod::Usage
    Getopt::ArgvFile
    File::Basename


==== INSTALLATION ====

To install this module, run the following commands:

    perl Build.PL
    ./Build
    ./Build test
    ./Build install

Or, if you're on a platform (like DOS or Windows) that doesn't like the "./"
notation, you can do this:

   perl Build.PL
   perl Build
   perl Build test
   perl Build install

In order to install somewhere other than the default, such as in a directory
under your home directory, like "/home/fred/perl" go

   perl Build.PL --install_base /home/fred/perl

as the first step instead.

This will install the files underneath /home/fred/perl.

You will then need to make sure that you alter the PERL5LIB variable to find
the modules, and the PATH variable to find the script.

Therefore you will need to change: your path, to include
/home/fred/perl/script (where the script will be)

        PATH=/home/fred/perl/script:${PATH}

the PERL5LIB variable to add /home/fred/perl/lib

        PERL5LIB=/home/fred/perl/lib:${PERL5LIB}


==== AUTHOR ====

    Kathryn Andersen (RUBYKAT)
    perlkat AT katspace dot com
    http://www.katspace.com


==== COPYRIGHT AND LICENCE ====

Copyright (c) 2004-2008 by Kathryn Andersen

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.

