Provided by: libtm-perl_1.56-10_all 
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.