NAME

       TM::Overview - Topic Maps, Overview

INTRODUCTION

       The TM suite of packages allows you to read and modify data organized according to the
       Topic Map paradigm.  It includes some drivers to read TM content from files, such as LTM
       or AsTMa=, but also a way to synchronize with MLDBM data files.

       The core functionality is enhanced in several ways: bulk transfer of TM content into your
       application, treating a set of maps as another map (mapsphere), map statistics and
       analysis, and converting a map taxonomy into a tree. There is also a way to index an
       existing map.

       The distribution also provides packages to handle 'virtual' topic maps, i.e. wrappers
       around other resources which can be accessed via a TM interface and a set of backend
       technologies to make topic maps persistent. There is also nascent support of a TMQL-like
       query language. There is also an experimental TMDM-layer.

OVERVIEW

       The set of classes and traits has evolved over several development stages and can be
       regarded as failry stable.

   TM Core
       At the core sits the class TM. This class implements a memory-based topic map store. With
       it, you can instantiate maps, fill them with content and extract it again using direct
       access methods for topic-like and association-like information. Its implementation
       paradigm is actually not TMDM, but the much more low-level TMRM. According to that a map
       consists mostly of assertions which are light-weight associations. With these,
       associations, topic names and occurrences are implemented.  The topics themselves are
       collaps in this model to simple focal points carrying only subject locator and subject
       indicator information.

       The search functionality is quite minimalistic, mostly provided by the functions
       "match_forall" and "match_exists".

   TM Traits
       The core functionality is extensible in many, many different ways. To allow a developer
       precise control over what he needs, these extensions are written as traits, i.e. a set of
       methods which can be added ad libitum to a TM object. Or, alternatively, you can create
       your own subclass of TM and mixin these traits as they suit you.

       Here are some of the more interesting traits:

       TM::Synchronizable
           With it you can not only attach a map to an external resource (this is actually done
           by another trait TM::ResourceAble), but also have methods to synchronize in (loading
           map content from the resource into memory) and synchronize out (saving map content to
           the resource).

           Some resources are serializable, i.e. the content is stored as a sequence of
           characters (symbols).  Examples are LTM, AsTMa, XTM, etc. files. For each of these
           exists parsers, usually tucked away in packages such as TM::Serializable::AsTMa,
           TM::Serializeable::LTM, etc.  Since some formats are more popular, dedicated classes
           for these exist: TM::Materialized::AsTMa, TM::Materialized::LTM, and so forth.

           Some resources are not serializable, but they are still synchronizable. One example of
           this is TM::Synchronizable::MLDBM which allows you to dump the whole map content into
           a MLDBM file.

       TM::Analysis, TM::Tree
           These packages allow you to compute some statistics of a map, but also to find the
           connected island, i.e. those parts of a map which are somehow linked together with
           associations. The tree package can analyze a map in respect to an inherent tree
           structure. One example are family trees.

       TM::MapSphere
           Since maps can store any information about the real world, they can also store
           information about other maps. In this sense you can embed maps into other maps. Here
           this is done by having one topic representing an embedded map. From then you can
           easily added meta-information about embedded maps, such as authorship, access control,
           etc.

           If you organize this hierarchically, then you end up with a tree of maps: The top-
           level map contains various things, among them child maps. And each of these children
           can link to further maps. In a sense this is a complete TM repository into which you
           can add maps (mount) and remove complete maps (umount).

       TM::Bulk
           Especially when building web frontends for TM servers, the communication events have
           to be minimized.  With TM::Bulk it is possible to learn a lot from a topic, instead of
           querying numerous times. There is also a first lookup function for names.

   Indexing
       Using a naive in-memory representation can be quite slow if you map gets big and the
       retrieval more complex. To improve the performance instances of TM::Index can be
       associated with the map. See for the subclasses TM::Index::Match,
       TM::Index::Characteristics, TM::Index::Reify.

       [from v1.54]: There is now a trait TM::IndexAble which you can attach to an existing map
       to get index support (experimental).

   TMDM
       The low-level data structures are not exactly what most application developers would
       expect when they come across Topic Maps. They are more familiar with the high-level TMDM.
       The package TM::DM tries to emulate this behaviour as closely as possible.

   Tau Expressions
       Still quite experimental (but cool) are Tau expressions which allow you to combine maps in
       various ways, not just add them together for merging. One example would be the expression

         file:test.atm > file:test.xtm

       which - when evaluated - will try to read AsTMa= content from the file "test.atm" and will
       try to save an XTM version of it into "test.xtm". More elaborate examples involve
       filtering:

         file:test.atm * urn:tau:statistics > io:stdout

       That would take the map from "test.atm" and would apply the converter "urn:tau:statistics"
       to it to compute the statistics of the map. The statistical information is represented as
       map as well; it will then be copied to STDOUT (which is default anyway).

       Tau expressions can also include TMQL queries and support any number of different formats
       (these are pluggable at compile and at run time).

Workbench "tm"

       The distribution contains one 'binary' "tm". It is a command-line oriented interface to
       manage topic map content. With it you can copy map, query them (soon) and transform them.
       The interface also introduces one global store, a mapsphere into which you can save one or
       more maps.

Tutorial: In-memory maps

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Tutorial: Associating Resources

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Tutorial: Adding Indices

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Tutorial: Analyzing Maps

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Tutorial: Managing MapSpheres

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Tutorial: Tau Expressions

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COPYRIGHT AND LICENSE

       Copyright 200[3-6] by Robert Barta, <drrho@cpan.org>

       This library is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.