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Biblio::ILL::ISO
================

Biblio::ILL::ISO is a module for handling ISO-protocol Interlibrary 
Loan messages.

According to the ISO standard maintained by the National Library of
Canada (http://www.nlc-bnc.ca/)
there are 20 message types:

   ILL-Request               Forward-Notification
   Shipped                   ILL-Answer
   Conditional-Reply         Cancel
   Cancel-Reply              Received
   Recall                    Returned
   Checked-In                Overdue
   Renew                     Renew-Answer
   Lost                      Damaged
   Message                   Status-Query
   Status-Or-Error-Report    Expired

Each of these message types is built up from a collection of basic
types (such as Transaction-Id, Service-Date-Time, Client-Id, etc).
There are about a hundred basic types.

In the Biblio::ILL::ISO module, each basic type is implemented as
an object derived from a common base, Biblio::ILL::ISO::ILLASNtype.
(the "special" types, ENUMERATED and SEQUENCE_OF, are also derived
from ILLASNtype, and have certain basic types derived from them in
turn).

All of the basic type objects are collected into one message-type
meta-object, Biblio::ILL::ISO::ISO, from which the various message-
type objects are derived.  Biblio::ILL::ISO::ISO.pm is best thought
of as a "pure virtual" class - it's just a base to derive the "real"
message-type classes.

+---------------------------------------+
| The 20 message-types                  |
+---------------------------------------+
| Biblio::ILL:ISO::ISO.pm               |
+---------------------------------------+
| The hundred or so basic-types         |
+-------------+--------------+----------+
|          | ENUMERATED  | SEQUENCE_OF  |
|          +-------------+--------------|
| Biblio::ILL::ISO::ILLASNtype.pm       |
+---------------------------------------+

To get a feel for how all this works, take a look at the scripts
in the pl/ directory (especially pl/ISO-msg-t-dumper.pm, which creates
the test cases for messages, and pl/ISO-t-dumper.pm, which creates
the test cases for basic types (if you want to dig that deeply)).

Messages are encoded to / decoded from BER-encoded files.

For encoding of messages, the module uses Convert::ASN1, which expects
a hash containing the data.  The objects implement an as_asn() method
which returns this hash (and is invoked in the message-type object's
encode() method).

Likewise, for decoding of messages, the module uses Convert::ASN1,
which returns a hash of the data.  The objects implement a from_asn()
method which builds the message-type object from this hash (and is
invoked in the message-type object's decode() method).

Fortunately, you shouldn't have to worry about all that.

Some "special" objects
----------------------
asn.pm                The ASN.1 definition from the ILL ISO 
		      Maintenance Agency (http://www.nlc-bnc.ca/).
		      The ASN.1 definition has been tweaked so that
		      Convert::ASN1 can understand it.

ENUMERATED.pm         A base object for building enumerated types 
		      (there are a lot of them - grep for ENUMERATED
		      in the lib/Biblio/ILL/ISO directory).

SEQUENCE_OF.pm	      A base object for building lists of other types
		      (there are a few of them).

ILLASNtype.pm	      The basic-types base object.

ISO.pm		      The message-types base object.

ILL_ASN_type_list.pm  A convenience.  Includes all of the basic-types
		      (to avoid having to retype it a hundred times!)

Some examples
-------------
In the pl/ directory, see ISOtypetest.pm, ISO-t-dumper.pm, and
ISO-msg-t-dumper.pm.

In the pl/messages directory, there are a read and a write script for
each of the message types.


Some caveats
------------
Currently, ASN.1 extension handling in Biblio::ILL::ISO doesn't work,
pending further understanding on my part ;-)  This is a big issue - all
message-types can make use of ASN.1 extensions - but it's not a 
show-stopper. According to the ASN.1 definition, the extensions are
optional.... Unfortunately, I suspect that they are common.



INSTALLATION

To install this module type the following:

   perl Makefile.PL
   make
   make test