NAME

       Tangram - Store pure objects in standard relational databases

SYNOPSIS

       See Tangram::Tour

DESCRIPTION

       Tangram is an object-relational mapper.  It is orthogonal, meaning that it does not
       require anything of the objects stored in it (other than the common convention that base
       objects be based upon HASHes; individual columns can be anything).

       It consists of a schema language that can describe or be built around an object structure,
       or so as to closely match an existing SQL schema (with some limitations).  This schema
       language is rich enough to express such common RDBMS features as links, foreign keys, and
       link tables.

       It also consists of a relational database storage engine, which based on the schema
       structure, will make Perl structures persist in a relational (SQL compliant) database.
       References to other objects (or collections, as represented with foreign keys and link
       tables) may be loaded using on demand references that `lazily' load data when it is
       needed.

       As of Tangram 2.08, the schema need not describe every single object property, so that you
       can map only the columns you intend to query.  The rest of the object is then stored in a
       column via a serialiser, like Data::Dumper, YAML or Storable.  These structures themselves
       may contain arbitrary references to other objects in storage.

       Tangram has soundly engineered transaction support, without sacrificing excellent data
       caching abilities.  The general optimisation strategy of the code makes it most suited for
       OLTP (aka application servers) and other situations where it is better to select and
       update whole rows than to worry about which columns to retrieve/update or not
       retrieve/update.

       Once your object are persistent, you can build query expressions to find them in terms of
       the schema language that you used to put them in.  Therefore, the schema data structure
       does not describe a data structure, it describes a data access pattern.

       If you are not picky about which accessor module to use, preferring to specify the schema
       once only, then you can use the separately distributed Class::Tangram::Generator to make a
       set of classes from a Tangram schema structure.

       If you are looking for a tool that implements SQL abstraction only, you have probably
       missed the point (of this module, anyway), and a well-supported module like Class::DBI, or
       an interactive SQL modeller like Alzabo will likely suit your needs better.

       Tangram is beginning to include preliminary support for aggregation functions, and
       currently supports grouping, summing and counting.  Joins must currently be in terms of
       integer primary key columns, to extend past this would require extra mapping types to be
       developed.  Basic support for alternative join types is present, but in its infancy.

       Tangram currently contains no support for database-side updates (ie, "UPDATE foo SET bar =
       'baz' where frop = 'blarg'"), but support is planned.

       There is no support for creating views based on existing classes to make new derived
       classes; you have to use your database SQL and create corresponding Tangram classes
       manually to do that.

       Tangram has a web site at <http://tangram.utsl.gen.nz/>, currently sponsored by MarketView
       (New Zealand) Ltd.

DOCUMENTATION INDEX

CONTENTS

       Tangram::Tour
           The original "Guided Tour" of the features of Tangram, by Jean-Louis Leroy.

       Tangram::Intro
           The humble beginnings of a new guided tour, based on the next-generation features
           found in Tangram 2.08.

       Tangram::Springfield
           The classes and schema used in the Guided Tour(s).

       Tangram::Storage
           The main database handle class.  Includes details on query syntax.

       Tangram::Cursor
           Return an iterator that retrieves persistent objects in a result set one by one.

       Tangram::Schema
           The Tangram schema structure - representing your data model so that Tangram can map
           it.

       Tangram::Relational::Mappings
           An informative text on exactly how Object Relational Mapping is accomplished by the
           Tangram::Relational back-end, what the different styles of mapping are, and how each
           is selected.

       Tangram::Type
           What Tangram types are available.  This page is an index of other manual pages that
           express the data and relationship types available in Tangram.

       Tangram::Type::Extending
           How to write your own custom types for Tangram.

       Tangram::Dialect
           Database-specific extensions to Tangram, such as Tangram::mysql and Tangram::Sybase.
           These extensions only add functionality, and are not required for core operation of
           Tangram.

COMPATIBILITY

       Tangram has been known to run in the following environments, however, Tangram uses
       standard SQL and should be usable with any SQL-83 compliant database.  Most of the
       requirements are simply avoiding the worst bugs.

       Note that some functions (e.g. transactions and subselects) may not be available in some
       environments. This is reported during the test suite.

       •   Perl 5.005_03+, 5.6.1+, 5.8.1+ (5.8.0 had a nasty bug and doesn't work with Tangram)

       •   Set::Object 1.04 (though the latest version is highly recommended)

       •   DBI 1.14

       •   DBD::mysql 2.0402

       •   DBD::Oracle 1.06

       •   DBD::Sybase 0.21

       •   DBD::SQLite 1.07

       •   DBD::Pg 0.93

LICENSE & WARRANTY

       You may use Tangram, free of charge, under the terms of the GPL.  This notice applies to
       the entire distribution and all of its parts.

       You can obtain a commercial license for old (2.04 and earlier) versions of Tangram from
       Sound Object Logic, see http://www.soundobjectlogic.com/tangram/licenses.html.

       TANGRAM COMES WITHOUT ANY WARRANTY OF ANY KIND.  IT DOES NOT EVEN COME WITH ANY KIND OF
       VAGUE IMPLICATION THAT IT DOES ANYTHING MORE THAN GIVE YOUR COMPUTER HINTS ABOUT HOW TO
       TRY STIRRING ITS ELECTRONS.  THE AUTHORS ARE NOT RESPONSIBLE FOR THE RESULTANT ELECTRON
       CONFIGURATION IN ANY WAY INCLUDING TRANSMUTATIONS OF ELECTRONS INTO OTHER FIELDS SUCH AS
       MAGNETIC MEDIA OR PUNCH CARDS.

SUPPORT

       Please send bug reports directly to the Tangram 2 maintainer's mailing list
       <t2-users@lists.utsl.gen.nz>, and please CC: <bug-Tangram@rt.cpan.org> so your fault can
       be tracked accurately.

       Whenever possible, include a short yet complete script demonstrating the problem.  (read:
       if you want it fixed quicker, demonstrate it)

       Questions of general interest should should be posted to the mailing list, but not sent to
       rt.cpan.org.

AUTHORS

       All the code and documentation for versions 2.04 and earlier, as well as some changes in
       the 2.05 release, were written by Jean-Louis Leroy (jll@soundobjectlogic.com) and Sound
       Object Logic.

       Sam Vilain <sam@vilain.net> is the author of the derived work that is Tangram 2.05 and
       later.

       Andres Kievsky <ank@cpan.org> has contributed to the Tangram code starting with Tangram
       2.08.