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TM::QL.3pm

NAME

TM::QL - Topic Maps, Query Language Expressions

SYNOPSIS

    use TM::QL;
    # compile a TMQL query (here path expression style)
    my $q = new TM::QL ('// hypocrite [ . <- employee -> organisation == $org ]');
 
    use TM;
    my $tm = new TM (....);                         # get a map from somewhere
 
    my $or  = $tm->mids ('vagabond-university');    # find internal id
    my $ts = $q->eval ('%_' => $tm,                 # explicitly pass in a default map
                       '$o' => $or);                # and any number of other variable bindings
 
    foreach my $tuple (@$ts) {                      # iterate through the tuple sequence
       foreach my $value (@$tuple) {                # do something with the tuple
         print ref ($value) 
                  ? $value->[0]                     # literal
                  : $value                          # internal map identifier
       }
    }
 
 

DESCRIPTION

This class implements TMQL expression handling. A TMQL expression can be parsed, stored in an object, optimized and then evaluated. The results of this process is a tuple sequence as described in

     http://topicmaps.it.bond.edu.au/junk/tmql.html
 
 

NOTE: This is work in progress, so there might be discrepancies.

Constructor

Given a TMQL query expression, this constructor will build a compiled version of the query, which then can be executed with the method "eval".

If an already compiled is passed as parameter, the constructor behaves as a cloner. (Note: no deep copy of the compiled query).

Methods

eval

Given a query object, this method will evaluate it according to the TMQL semantics. The result is a tuple sequence (TM::QL::TS).

Optionally, a hash reference can be passed into this method. It will be used as variable binding.

AUTHOR

Robert Barta, <drrho@cpan.org>

COPYRIGHT AND LICENSE

Copyright (C) 200[4-6] by Robert Barta

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.4 or, at your option, any later version of Perl 5 you may have available.