-# $Id: ZOOM.pod,v 1.16 2005-12-13 14:01:59 mike Exp $
+# $Id: ZOOM.pod,v 1.20 2005-12-13 16:03:14 mike Exp $
use strict;
use warnings;
=head2 ZOOM::Query
-I<###>
+ $q = new ZOOM::Query::CQL("creator=pike and subject=unix");
+ $q->sortby("1=4 >i 1=21 >s");
+ $rs = $conn->search($q);
+ $q->destroy();
+
+C<ZOOM::Query> is a virtual base class from which various concrete
+subclasses can be derived. Different subclasses implement different
+types of query. The sole purpose of a Query object is to be used in a
+C<search()> on a Connection; because PQF is such a common special
+case, the shortcut Connection method C<search_pqf()> is provided.
+
+The following Query subclasses are provided, both of the providing the
+same set of methods described below:
+
+=over 4
+
+=item ZOOM::Query::PQF
+
+Implements Prefix Query Format (PQF), also sometimes known as Prefix
+Query Notation (PQN). This esoteric but rigorous and expressive
+format is described in the YAZ Manual at
+http://indexdata.com/yaz/doc/tools.tkl#PQF
+
+=item ZOOM::Query::CQL
+
+Implements the Common Query Language (CQL) of SRU, the Search/Retrieve
+URL. CQL is a much friendlier notation than PQF, using a simple infix
+notation. The queries are passed ``as is'' to the server rather than
+being compiled into a Z39.50 Type-1 query, so only CQL-compliant
+servers can support such querier. CQL is described at
+http://www.loc.gov/standards/sru/cql/
+and in a slight out-of-date but nevertheless useful tutorial at
+http://zing.z3950.org/cql/intro.html
+
+=back
+
+See the description of the C<Query> class in the ZOOM Abstract
+API at
+http://zoom.z3950.org/api/zoom-current.html#3.3
+
+=head3 Methods
+
+=head4 new()
+
+ $q = new ZOOM::Query::CQL('title=dinosaur'));
+ $q = new ZOOM::Query::PQF('@attr 1=4 dinosaur'));
+
+Creates a new query object, compiling the query passed as its argument
+according to the rules of the particular query-type being
+instantiated. If compilation fails, an exception is thrown.
+Otherwise, the query may be passed to the C<Connection> method
+<search()>.
+
+=head4 sortby()
+
+ $q->sortby("1=4 >i 1=21 >s");
+
+Sets a sort specification into the query, so that when a C<search()>
+is run on the query, the result is automatically sorted. The sort
+specification language is the same as the C<yaz> sort-specification
+type of the C<ResultSet> method C<sort()>, described above.
+
+B<It ought to be possible to sort by CQL query, too, but at present
+limitations in the underlying ZOOM-C library make this impossible.>
+
+=head4 destroy()
+
+ $p->destroy()
+
+Destroys a Query object, freeing its resources. It is an error to
+reuse a Query that has been C<destroy()>ed.
=head2 ZOOM::Options
+ $o1 = new ZOOM::Options();
+ $o1->option(user => "alf");
+ $o2 = new ZOOM::Options();
+ $o2->option(password => "fruit");
+ $opts = new ZOOM::Options($o1, $o2);
+ $conn = create ZOOM::Connection($opts);
+ $conn->connect($host); # Uses the specified username and password
+
+Several classes of ZOOM objects carry their own sets of options, which
+can be manipulated using their C<option()> method. Sometimes,
+however, it's useful to deal with the option sets directly, and the
+C<ZOOM::Options> class exists to enable this approach.
+
+Option sets are B<not currently described> in the ZOOM
+Abstract API at
+http://zoom.z3950.org/api/zoom-current.html
+They are an extension to that specification.
+
+=head3 Methods
+
+=head4 new()
+
+ $o1 = new ZOOM::Options();
+ $o1and2 = new ZOOM::Options($o1);
+ $o3 = new ZOOM::Options();
+ $o1and3and4 = new ZOOM::Options($o1, $o3);
+
+Creates and returns a new option set. One or two (but no more)
+existing option sets may be passed as arguments, in which case they
+become ``parents'' of the new set, which thereby ``inherits'' their
+options, the values of the first parent overriding those of the second
+when both have a value for the same key. An option set that inherits
+from a parent that has its own parents also inherits the grandparent's
+options, and so on.
+
+=head4 option() / option_binary()
+
+ $o->option(preferredRecordSyntax => "usmarc");
+ $o->option_binary(iconBlob => "foo\0bar");
+ die if length($o->option_binary("iconBlob") != 7);
+
+These methods are used to get and set options within a set, and behave
+the same way as the same-named C<Connection> methods - see above. As
+with the C<Connection> methods, values passed to and retrieved using
+C<option()> are interpreted as NUL-terminated, while those passed to
+and retrieved from C<option_binary()> are binary-clean.
+
+=head4 bool()
+
+ $o->option(x => "T");
+ $o->option(y => "F");
+ assert($o->bool("x", 1));
+ assert(!$o->bool("y", 1));
+ assert($o->bool("z", 1));
+
+The first argument is a key, and the second is a default value.
+Returns the value associated with the specified key as a boolean, or
+the default value if the key has not been set. The values C<T> (upper
+case) and C<1> are considered true; all other values (including C<t>
+(lower case) and non-zero integers other than one) are considered
+false.
+
+This method is provided in ZOOM-C because in a statically typed
+language it's convenient to have the result returned as an
+easy-to-test type. In a dynamically typed language such as Perl, this
+problem doesn't arise, so C<bool()> is nearly useless; but it is made
+available in case applications need to duplicate the idiosyncratic
+interpretation of truth and falsehood and ZOOM-C uses.
+
+=head4 int()
+
+ $o->option(x => "012");
+ assert($o->int("x", 20) == 12);
+ assert($o->int("y", 20) == 20);
+
+Returns the value associated with the specified key as an integer, or
+the default value if the key has not been set. See the description of
+C<bool()> for why you almost certainly don't want to use this.
+
+=head4 set_int()
+
+ $o->set_int(x => "29");
+
+Sets the value of the specified option as an integer. Of course, Perl
+happily converts strings to integers on its own, so you can just use
+C<option()> for this, but C<set_int()> is guaranteed to use the same
+string-to-integer conversion as ZOOM-C does, which might occasionally
+be useful. Though I can't imagine how.
+
+=head4 set_callback()
+
I<###>
+=head4 destroy()
+
+ $o->destroy()
+
+Destroys an Options object, freeing its resources. It is an error to
+reuse an Options object that has been C<destroy()>ed.
+
=head1 ENUMERATIONS
The ZOOM module provides two enumerations that list possible return
projects / ZOOM-Perl-moved-to-github.git / blobdiff