+## This file is part of simpleserver
+## Copyright (C) 2000-2011 Index Data.
+## All rights reserved.
+## Redistribution and use in source and binary forms, with or without
+## modification, are permitted provided that the following conditions are met:
##
-## Copyright (c) 2000, Index Data.
-##
-## Permission to use, copy, modify, distribute, and sell this software and
-## its documentation, in whole or in part, for any purpose, is hereby granted,
-## provided that:
-##
-## 1. This copyright and permission notice appear in all copies of the
-## software and its documentation. Notices of copyright or attribution
-## which appear at the beginning of any file must remain unchanged.
-##
-## 2. The name of Index Data or the individual authors may not be used to
-## endorse or promote products derived from this software without specific
-## prior written permission.
-##
-## THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTY OF ANY KIND,
-## EXPRESS, IMPLIED, OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
-## WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-## IN NO EVENT SHALL INDEX DATA BE LIABLE FOR ANY SPECIAL, INCIDENTAL,
-## INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, OR ANY DAMAGES
-## WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER OR
-## NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
-## LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
-## OF THIS SOFTWARE.
-##
-##
-
-## $Log: SimpleServer.pm,v $
-## Revision 1.6 2001-03-13 14:17:15 sondberg
-## Added support for GRS-1.
+## * Redistributions of source code must retain the above copyright
+## notice, this list of conditions and the following disclaimer.
+## * Redistributions in binary form must reproduce the above copyright
+## notice, this list of conditions and the following disclaimer in the
+## documentation and/or other materials provided with the distribution.
+## * Neither the name of Index Data nor the names of its contributors
+## may be used to endorse or promote products derived from this
+## software without specific prior written permission.
##
+## THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
+## EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+## WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+## DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
+## DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+## (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+## LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+## ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+## (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+## THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package Net::Z3950::SimpleServer;
require AutoLoader;
@ISA = qw(Exporter AutoLoader DynaLoader);
-# Items to export into callers namespace by default. Note: do not export
-# names by default without a very good reason. Use EXPORT_OK instead.
-# Do not simply export all your public functions/methods/constants.
-@EXPORT = qw(
-
-);
-$VERSION = '0.02';
+@EXPORT = qw( );
+$VERSION = '1.15';
bootstrap Net::Z3950::SimpleServer $VERSION;
sub new {
my $class = shift;
- my $args = shift || croak "SimpleServer::new: Usage new(argument hash)";
- my $self = {};
+ my %args = @_;
+ my $self = \%args;
if ($count) {
carp "SimpleServer.pm: WARNING: Multithreaded server unsupported";
}
$count = 1;
- $self->{INIT} = $args->{INIT};
- $self->{SEARCH} = $args->{SEARCH} || croak "SimpleServer.pm: ERROR: Unspecified search handler";
- $self->{FETCH} = $args->{FETCH} || croak "SimpleServer.pm: ERROR: Unspecified fetch handler";
- $self->{CLOSE} = $args->{CLOSE};
- $self->{PRESENT} = $args->{PRESENT};
+ croak "SimpleServer.pm: ERROR: Unspecified search handler" unless defined($self->{SEARCH});
+ croak "SimpleServer.pm: ERROR: Unspecified fetch handler" unless defined($self->{FETCH});
bless $self, $class;
return $self;
my $self = shift;
my @args = @_;
+ ### This modal internal interface, in which we set a bunch of
+ # globals and then call start_server(), is asking for
+ # trouble. Instead, we should just pass the $self object
+ # as a parameter into start_server().
+ if (defined($self->{GHANDLE})) {
+ set_ghandle($self->{GHANDLE});
+ }
if (defined($self->{INIT})) {
set_init_handler($self->{INIT});
}
if (defined($self->{PRESENT})) {
set_present_handler($self->{PRESENT});
}
-
+ if (defined($self->{SCAN})) {
+ set_scan_handler($self->{SCAN});
+ }
+ if (defined($self->{SORT})) {
+ set_sort_handler($self->{SORT});
+ }
+ if (defined($self->{EXPLAIN})) {
+ set_explain_handler($self->{EXPLAIN});
+ }
+ if (defined($self->{DELETE})) {
+ set_delete_handler($self->{DELETE});
+ }
+ if (defined($self->{START})) {
+ set_start_handler($self->{START});
+ }
start_server(@args);
}
+# Register packages that we will use in translated RPNs
+package Net::Z3950::RPN::Node;
+package Net::Z3950::APDU::Query;
+our @ISA = qw(Net::Z3950::RPN::Node);
+package Net::Z3950::APDU::OID;
+package Net::Z3950::RPN::And;
+our @ISA = qw(Net::Z3950::RPN::Node);
+package Net::Z3950::RPN::Or;
+our @ISA = qw(Net::Z3950::RPN::Node);
+package Net::Z3950::RPN::AndNot;
+our @ISA = qw(Net::Z3950::RPN::Node);
+package Net::Z3950::RPN::Term;
+our @ISA = qw(Net::Z3950::RPN::Node);
+package Net::Z3950::RPN::RSID;
+our @ISA = qw(Net::Z3950::RPN::Node);
+package Net::Z3950::RPN::Attributes;
+package Net::Z3950::RPN::Attribute;
+package Net::Z3950::FacetList;
+package Net::Z3950::FacetField;
+package Net::Z3950::FacetTerms;
+package Net::Z3950::FacetTerm;
+
+
+# Utility method for re-rendering Type-1 query back down to PQF
+package Net::Z3950::RPN::Node;
+
+sub toPQF {
+ my $this = shift();
+ my $class = ref $this;
+
+ if ($class eq "Net::Z3950::APDU::Query") {
+ my $res = "";
+ my $set = $this->{attributeSet};
+ $res .= "\@attrset $set " if defined $set;
+ return $res . $this->{query}->toPQF();
+ } elsif ($class eq "Net::Z3950::RPN::Or") {
+ return '@or ' . $this->[0]->toPQF() . ' ' . $this->[1]->toPQF();
+ } elsif ($class eq "Net::Z3950::RPN::And") {
+ return '@and ' . $this->[0]->toPQF() . ' ' . $this->[1]->toPQF();
+ } elsif ($class eq "Net::Z3950::RPN::AndNot") {
+ return '@not ' . $this->[0]->toPQF() . ' ' . $this->[1]->toPQF();
+ } elsif ($class eq "Net::Z3950::RPN::RSID") {
+ return '@set ' . $this->{id};
+ } elsif ($class ne "Net::Z3950::RPN::Term") {
+ die "unknown PQF node-type '$class'";
+ }
+
+ my $res = "";
+ foreach my $attr (@{ $this->{attributes} }) {
+ $res .= "\@attr ";
+ my $set = $attr->{attributeSet};
+ $res .= "$set " if defined $set;
+ $res .= $attr->{attributeType} . "=" . $attr->{attributeValue} . " ";
+ }
+
+ return $res . $this->{term};
+}
+
+
+# Must revert to original package for Autoloader's benefit
+package Net::Z3950::SimpleServer;
+
+
# Autoload methods go after =cut, and are processed by the autosplit program.
1;
my $set_id = $args->{SETNAME};
- my $record = fetch_a_record($args->{OFFSET);
+ my $record = fetch_a_record($args->{OFFSET});
$args->{RECORD} = $record;
if (number_of_hits() == $args->{OFFSET}) { ## Last record in set?
}
}
-
## Register custom event handlers:
+ my $z = new Net::Z3950::SimpleServer(GHANDLE = $someObject,
+ INIT => \&my_init_handler,
+ CLOSE => \&my_close_handler,
+ SEARCH => \&my_search_handler,
+ FETCH => \&my_fetch_handler);
- my $handle = Net::Z3950::SimpleServer->new({
- INIT => \&my_init_handler,
- CLOSE => \&my_close_handler,
- SEARCH => \&my_search_handler,
- FETCH => \&my_fetch_handler
- });
## Launch server:
-
- $handle->launch_server("ztest.pl", @ARGV);
+ $z->launch_server("ztest.pl", @ARGV);
=head1 DESCRIPTION
retrieving the results in the form of structured "records". It is widely
used in libraries around the world, as well as in the US Federal Government.
In addition, it is generally useful whenever you wish to integrate a number
-of different database systems around a shared, asbtract data model.
+of different database systems around a shared, abstract data model.
The model of the module is simple: It implements a "generic" Z39.50
server, which invokes callback functions supplied by you to search
The programmer can specify subroutines to take care of the following type
of events:
+ - Start service (called once).
- Initialize request
- Search request
- Present request
- Fetching of records
+ - Scan request (browsing)
- Closing down connection
Note that only the Search and Fetch handler functions are required.
the Perl script to the server. The server calls the registered
subroutines to field incoming requests from Z39.50 clients.
-A reference to an anonymous hash is passed to each handle. Some of
+A reference to an anonymous hash is passed to each handler. Some of
the entries of these hashes are to be considered input and others
output parameters.
-The Perl programmer specifies the event handles for the server by
-means of the the SimpleServer object constructor
-
- my $handle = Net::Z3950::SimpleServer->new({
- INIT => \&my_init_handler,
- CLOSE => \&my_close_handler,
- SEARCH => \&my_search_handler,
- PRESENT => \&my_present_handler,
- FETCH => \&my_fetch_handler });
-
-After the custom event handles are declared, the server is launched
+The Perl programmer specifies the event handlers for the server by
+means of the SimpleServer object constructor
+
+ my $z = new Net::Z3950::SimpleServer(
+ START => \&my_start_handler,
+ INIT => \&my_init_handler,
+ CLOSE => \&my_close_handler,
+ SEARCH => \&my_search_handler,
+ PRESENT => \&my_present_handler,
+ SCAN => \&my_scan_handler,
+ FETCH => \&my_fetch_handler,
+ EXPLAIN => \&my_explain_handler,
+ DELETE => \&my_delete_handler,
+ SORT => \&my_sort_handler);
+
+In addition, the arguments to the constructor may include GHANDLE, a
+global handle which is made available to each invocation of every
+callback function. This is typically a reference to either a hash or
+an object.
+
+If you want your SimpleServer to start a thread (threaded mode) to
+handle each incoming Z39.50 request instead of forking a process
+(forking mode), you need to register the handlers by symbol rather
+than by code reference. Thus, in threaded mode, you will need to
+register your handlers this way:
+
+ my $z = new Net::Z3950::SimpleServer(
+ INIT => "my_package::my_init_handler",
+ CLOSE => "my_package::my_close_handler",
+ ....
+ .... );
+
+where my_package is the Perl package in which your handler is
+located.
+
+After the custom event handlers are declared, the server is launched
by means of the method
- $handle->launch_server("MyServer.pl", @ARGV);
+ $z->launch_server("MyServer.pl", @ARGV);
Notice, the first argument should be the name of your server
script (for logging purposes), while the rest of the arguments
are documented in the YAZ toolkit manual: The section on
-application invocation: <http://www.indexdata.dk/yaz/yaz-7.php>
+application invocation: <http://indexdata.com/yaz/doc/server.invocation.tkl>
+
+In particular, you need to use the -T switch to start your SimpleServer
+in threaded mode.
+
+=head2 Start handler
+
+The start handler is called when service is started. The argument hash
+passed to the start handler has the form
+
+ $args = {
+ CONFIG => "default-config" ## GFS config (as given by -c)
+ };
+
+
+The purpose of the start handler is to read the configuration file
+for the Generic Frontend Server . This is specified by option -c.
+If -c is omitted, the configuration file is set to "default-config".
+
+The start handler is optional. It is supported in Simpleserver 1.16 and
+later.
=head2 Init handler
$args = {
## Response parameters:
+ PEER_NAME => "", ## Name or IP address of connecting client
+ IMP_ID => "", ## Z39.50 Implementation ID
IMP_NAME => "", ## Z39.50 Implementation name
IMP_VER => "", ## Z39.50 Implementation version
ERR_CODE => 0, ## Error code, cnf. Z39.50 manual
+ ERR_STR => "", ## Error string (additional info.)
+ USER => "xxx" ## If Z39.50 authentication is used,
+ ## this member contains user name
+ PASS => "yyy" ## Under same conditions, this member
+ ## contains the password in clear text
+ GHANDLE => $obj ## Global handler specified at creation
HANDLE => undef ## Handler of Perl data structure
};
it is always best to store them in a private session structure -
rather than leaving them in global variables in your script.
-The Implementation name and version are only really used by Z39.50
+The Implementation ID, name and version are only really used by Z39.50
client developers to see what kind of server they're dealing with.
Filling these in is optional.
The ERR_CODE should be left at 0 (the default value) if you wish to
accept the connection. Any other value is interpreted as a failure
-and the client will be shown the door.
+and the client will be shown the door, with the code and the
+associated additional information, ERR_STR returned.
=head2 Search handler
$args = {
## Request parameters:
+ GHANDLE => $obj ## Global handler specified at creation
HANDLE => ref, ## Your session reference.
SETNAME => "id", ## ID of the result set
REPL_SET => 0, ## Replace set if already existing?
DATABASES => ["xxx"], ## Reference to a list of data-
## bases to search
QUERY => "query", ## The query expression
+ RPN => $obj, ## Reference to a Net::Z3950::APDU::Query
## Response parameters:
- ERR_CODE => 0, ## Error code (0=Succesful search)
+ ERR_CODE => 0, ## Error code (0=Successful search)
ERR_STR => "", ## Error string
HITS => 0 ## Number of matches
};
try to return good error codes if you run into something you can't or
won't support.
+A more convenient alternative to the QUERY member may be the RPN
+member, which is a reference to a Net::Z3950::APDU::Query object
+representing the RPN query tree. The structure of that object is
+supposed to be self-documenting, but here's a brief summary of what
+you get:
+
+=over 4
+
+=item *
+
+C<Net::Z3950::APDU::Query> is a hash with two fields:
+
+Z<>
+
+=over 4
+
+=item C<attributeSet>
+
+Optional. If present, it is a reference to a
+C<Net::Z3950::APDU::OID>. This is a string of dot-separated integers
+representing the OID of the query's top-level attribute set.
+
+=item C<query>
+
+Mandatory: a reference to the RPN tree itself.
+
+=back
+
+=item *
+
+Each node of the tree is an object of one of the following types:
+
+Z<>
+
+=over 4
+
+=item C<Net::Z3950::RPN::And>
+
+=item C<Net::Z3950::RPN::Or>
+
+=item C<Net::Z3950::RPN::AndNot>
+
+These three classes are all arrays of two elements, each of which is a
+node of one of the above types.
+
+=item C<Net::Z3950::RPN::Term>
+
+See below for details.
+
+=item C<Net::Z3950::RPN::RSID>
+
+A reference to a result-set ID indicating a previous search. The ID
+of the result-set is in the C<id> element.
+
+=back
+
+=back
+
+=over 4
+
+=item *
+
+C<Net::Z3950::RPN::Term> is a hash with two fields:
+
+Z<>
+
+=over 4
+
+=item C<term>
+
+A string containing the search term itself.
+
+=item C<attributes>
+
+A reference to a C<Net::Z3950::RPN::Attributes> object.
+
+=back
+
+=item *
+
+C<Net::Z3950::RPN::Attributes> is an array of references to
+C<Net::Z3950::RPN::Attribute> objects. (Note the plural/singular
+distinction.)
+
+=item *
+
+C<Net::Z3950::RPN::Attribute> is a hash with three elements:
+
+Z<>
+
+=over 4
+
+=item C<attributeSet>
+
+Optional. If present, it is dot-separated OID string, as above.
+
+=item C<attributeType>
+
+An integer indicating the type of the attribute - for example, under
+the BIB-1 attribute set, type 1 indicates a ``use'' attribute, type 2
+a ``relation'' attribute, etc.
+
+=item C<attributeValue>
+
+An integer or string indicating the value of the attribute - for example, under
+BIB-1, if the attribute type is 1, then value 4 indicates a title
+search and 7 indicates an ISBN search; but if the attribute type is
+2, then value 4 indicates a ``greater than or equal'' search, and 102
+indicates a relevance match.
+
+=back
+
+=back
+
+All of these classes except C<Attributes> and C<Attribute> are
+subclasses of the abstract class C<Net::Z3950::RPN::Node>. That class
+has a single method, C<toPQF()>, which may be used to turn an RPN
+tree, or part of one, back into a textual prefix query.
+
+Note that, apart to C<toPQF()>, none of these classes have any methods at
+all: the blessing into classes is largely just a documentation thing
+so that, for example, if you do
+
+ { use Data::Dumper; print Dumper($args->{RPN}) }
+
+you get something fairly human-readable. But of course, the type
+distinction between the three different kinds of boolean node is
+important.
+
+By adding your own methods to these classes (building what I call
+``augmented classes''), you can easily build code that walks the tree
+of the incoming RPN. Take a look at C<samples/render-search.pl> for a
+sample implementation of such an augmented classes technique.
+
+
=head2 Present handler
The presence of a present handler in a SimpleServer front-end is optional.
sets are likely to occur, the implementation of a reasonable present
handler can gain performance significantly.
-The informations exchanged between client and present handle are:
+The information exchanged between client and present handle is:
$args = {
## Client/server request:
+ GHANDLE => $obj ## Global handler specified at creation
HANDLE => ref, ## Reference to datastructure
SETNAME => "id", ## Result set ID
START => xxx, ## Start position
NUMBER => yyy, ## Number of requested records
- ## Respons parameters:
+ ## Response parameters:
HITS => zzz, ## Number of returned records
ERR_CODE => 0, ## Error code
$args = {
## Client/server request:
+ GHANDLE => $obj ## Global handler specified at creation
HANDLE => ref ## Reference to data structure
SETNAME => "id" ## ID of the requested result set
OFFSET => nnn ## Record offset number
REQ_FORM => "n.m.k.l"## Client requested format OID
COMP => "xyz" ## Formatting instructions
+ SCHEMA => "abc" ## Requested schema, if any
## Handler response:
ERR_STR => "" ## Error string
SUR_FLAG => 0 ## Surrogate diagnostic flag
REP_FORM => "n.m.k.l"## Provided format OID
+ SCHEMA => "abc" ## Provided schema, if any
};
The REP_FORM value has by default the REQ_FORM value but can be set to
NOTE: The record offset is 1-indexed - 1 is the offset of the first
record in the set.
+=head2 Scan handler
+
+A full featured Z39.50 server should support scan (or in some literature
+browse). The client specifies a starting term of the scan, and the server
+should return an ordered list of specified length consisting of terms
+actually occurring in the data base. Each of these terms should be close
+to or equal to the term originally specified. The quality of scan compared
+to simple search is a guarantee of hits. It is simply like browsing through
+an index of a book, you always find something! The parameters exchanged are
+
+ $args = {
+ ## Client request
+
+ GHANDLE => $obj, ## Global handler specified at creation
+ HANDLE => $ref, ## Reference to data structure
+ DATABASES => ["xxx"], ## Reference to a list of data-
+ ## bases to search
+ TERM => 'start', ## The start term
+ RPN => $obj, ## Reference to a Net::Z3950::RPN::Term
+
+ NUMBER => xx, ## Number of requested terms
+ POS => yy, ## Position of starting point
+ ## within returned list
+ STEP => 0, ## Step size
+
+ ## Server response
+
+ ERR_CODE => 0, ## Error code
+ ERR_STR => '', ## Diagnostic message
+ NUMBER => zz, ## Number of returned terms
+ STATUS => $status, ## ScanSuccess/ScanFailure
+ ENTRIES => $entries ## Referenced list of terms
+ };
+
+where the term list is returned by reference in the scalar $entries, which
+should point at a data structure of this kind,
+
+ my $entries = [
+ { TERM => 'energy',
+ OCCURRENCE => 5 },
+
+ { TERM => 'energy density',
+ OCCURRENCE => 6, },
+
+ { TERM => 'energy flow',
+ OCCURRENCE => 3 },
+
+ ...
+
+ ...
+ ];
+
+The $status flag is only meaningful after a successful scan, and
+should be assigned one of two values:
+
+ Net::Z3950::SimpleServer::ScanSuccess Full success (default)
+ Net::Z3950::SimpleServer::ScanPartial Fewer terms returned than requested
+
+The STEP member contains the requested number of entries in the term-list
+between two adjacent entries in the response.
+
+A better alternative to the TERM member is the the RPN
+member, which is a reference to a Net::Z3950::RPN::Term object
+representing the scan clause. The structure of that object is the
+same as for Term objects included as part of the RPN tree passed to
+search handlers. This is more useful than the simple TERM because it
+includes attributes (e.g. access points associated with the term),
+which are discarded by the TERM element.
+
=head2 Close handler
-The argument hash recieved by the close handler has one element only:
+The argument hash received by the close handler has two elements only:
$args = {
## Server provides:
+
+ GHANDLE => $obj ## Global handler specified at creation
HANDLE => ref ## Reference to data structure
};
after this call. If you need to close down a connection to your server
or something similar, this is the place to do it.
+=head2 Delete handler
+
+The argument hash received by the delete handler has the following elements:
+
+ $args = {
+ ## Client request:
+ GHANDLE => $obj, ## Global handler specified at creation
+ HANDLE => ref, ## Reference to data structure
+ SETNAME => "id", ## Result set ID
+
+ ## Server response:
+ STATUS => 0 ## Deletion status
+ };
+
+The SETNAME element of the argument hash may or may not be defined.
+If it is, then SETNAME is the name of a result set to be deleted; if
+not, then all result-sets associated with the current session should
+be deleted. In either case, the callback function should report on
+success or failure by setting the STATUS element either to zero, on
+success, or to an integer from 1 to 10, to indicate one of the ten
+possible failure codes described in section 3.2.4.1.4 of the Z39.50
+standard -- see
+http://www.loc.gov/z3950/agency/markup/05.html#Delete-list-statuses1
+
+=head2 Sort handler
+
+The argument hash received by the sort handler has the following elements:
+
+ $args = {
+ ## Client request:
+ GHANDLE => $obj, ## Global handler specified at creation
+ HANDLE => ref, ## Reference to data structure
+ INPUT => [ a, b ... ], ## Names of result-sets to sort
+ OUTPUT => "name", ## Name of result-set to sort into
+ SEQUENCE ## Sort specification: see below
+
+ ## Server response:
+ STATUS => 0, ## Success, Partial or Failure
+ ERR_CODE => 0, ## Error code
+ ERR_STR => '', ## Diagnostic message
+
+ };
+
+The SEQUENCE element is a reference to an array, each element of which
+is a hash representing a sort key. Each hash contains the following
+elements:
+
+=over 4
+
+=item RELATION
+
+0 for an ascending sort, 1 for descending, 3 for ascending by
+frequency, or 4 for descending by frequency.
+
+=item CASE
+
+0 for a case-sensitive sort, 1 for case-insensitive
+
+=item MISSING
+
+How to respond if one or more records in the set to be sorted are
+missing the fields indicated in the sort specification. 1 to abort
+the sort, 2 to use a "null value", 3 if a value is provided to use in
+place of the missing data (although in the latter case, the actual
+value to use is currently not made available, so this is useless).
+
+=back
+
+And one or other of the following:
+
+=over 4
+
+=item SORTFIELD
+
+A string indicating the field to be sorted, which the server may
+interpret as it sees fit (presumably by an out-of-band agreement with
+the client).
+
+=item ELEMENTSPEC_TYPE and ELEMENTSPEC_VALUE
+
+I have no idea what this is.
+
+=item ATTRSET and SORT_ATTR
+
+ATTRSET is the attribute set from which the attributes are taken, and
+SORT_ATTR is a reference to an array containing the attributes
+themselves. Each attribute is represented by (are you following this
+carefully?) yet another hash, this one containing the elements
+ATTR_TYPE and ATTR_VALUE: for example, type=1 and value=4 in the BIB-1
+attribute set would indicate access-point 4 which is title, so that a
+sort of title is requested.
+
+=back
+
+Precisely why all of the above is so is not clear, but goes some way
+to explain why, in the Z39.50 world, the developers of the standard
+are not so much worshiped as blamed.
+
+The backend function should set STATUS to 0 on success, 1 for "partial
+success" (don't ask) or 2 on failure, in which case ERR_CODE and
+ERR_STR should be set.
+
+=head2 Support for SRU and SRW
+
+Since release 1.0, SimpleServer includes support for serving the SRU
+and SRW protocols as well as Z39.50. These ``web-friendly'' protocols
+enable similar functionality to that of Z39.50, but by means of rich
+URLs in the case of SRU, and a SOAP-based web-service in the case of
+SRW. These protocols are described at
+http://www.loc.gov/sru
+
+In order to serve these protocols from a SimpleServer-based
+application, it is necessary to launch the application with a YAZ
+Generic Frontend Server (GFS) configuration file, which can be
+specified using the command-line argument C<-f> I<filename>. A
+minimal configuration file looks like this:
+
+ <yazgfs>
+ <server>
+ <cql2rpn>pqf.properties</cql2rpn>
+ </server>
+ </yazgfs>
+
+This file specifies only that C<pqf.properties> should be used to
+translate the CQL queries of SRU and SRW into corresponding Z39.50
+Type-1 queries. For more information about YAZ GFS configuration,
+including how to specify an Explain record, see the I<Virtual Hosts>
+section of the YAZ manual at
+http://indexdata.com/yaz/doc/server.vhosts.tkl
+
+The mapping of CQL queries into Z39.50 Type-1 queries is specified by
+a file that indicates which BIB-1 attributes should be generated for
+each CQL index, relation, modifiers, etc. A typical section of this
+file looks like this:
+
+ index.dc.title = 1=4
+ index.dc.subject = 1=21
+ index.dc.creator = 1=1003
+ relation.< = 2=1
+ relation.le = 2=2
+
+This file specifies the BIB-1 access points (type=1) for the Dublin
+Core indexes C<title>, C<subject> and C<creator>, and the BIB-1
+relations (type=2) corresponding to the CQL relations C<E<lt>> and
+C<E<lt>=>. For more information about the format of this file, see
+the I<CQL> section of the YAZ manual at
+http://indexdata.com/yaz/doc/tools.tkl#tools.cql
+
+The YAZ distribution include a sample CQL-to-PQF mapping configuration
+file called C<pqf.properties>; this is sufficient for many
+applications, and a good base to work from for most others.
+
+If a SimpleServer-based application is run without this SRU-specific
+configuration, it can still serve SRU; however, CQL queries will not
+be translated, but passed straight through to the search-handler
+function, as the C<CQL> member of the parameters hash. It is then the
+responsibility of the back-end application to parse and handle the CQL
+query, which is most easily done using Ed Summers' fine C<CQL::Parser>
+module, available from CPAN at
+http://search.cpan.org/~esummers/CQL-Parser/
+
=head1 AUTHORS
-Anders Sønderberg (sondberg@indexdata.dk) and Sebastian Hammer
-(quinn@indexdata.dk).
+Anders Sønderberg (sondberg@indexdata.dk),
+Sebastian Hammer (quinn@indexdata.dk),
+Mike Taylor (indexdata.com).
-=head1 SEE ALSO
+=head1 COPYRIGHT AND LICENCE
-perl(1).
+Copyright (C) 2000-2011 by Index Data.
-Any Perl module which is useful for accessing the database of your
-choice.
+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.
-=cut
+=head1 SEE ALSO
+Any Perl module which is useful for accessing the data source of your
+choice.
+=cut