Ubuntu Manpage: TM::DM - Topic Maps, read-only TMDM layer

NAME

       TM::DM - Topic Maps, read-only TMDM layer

SYNOPSIS

          # somehow acquire a map (see TM and its subclasses)
          my $tm = ....

          # put a TMDM layer on top of it
          use TM::DM;
          my $tmdm = new TM::DM (map => $tm);

          # get the TMDM topic map item
          my $topicmap = $tmdm->topicmap;

          # ask for all topics
          my @topics = $topicmap->topics;
          # for all associations
          my @assocs = $topicmap->associations;

          # get a particular topic
          my $adam = $topicmap->topic ('adam');

          # get some of its properties
          $adam->id;
          $adam->subjectLocators;
          $adam->subjectIdentifiers;
          $adam->parent;
          my @ns = $adam->names;
          my @os = $adam->occurrences;

          # similar for assocs
          my @as = $topicmap->associations (iplayer => 'adam');
          $as[0]->type;
          $as[0]->parent;
          my @rs = $as[0]->roles;

ABSTRACT

       This package provides a TMDM-ish (read-only) view on an existing topic map.

DESCRIPTION

       TMDM, the Topic Maps Data Model

          http://www.isotopicmaps.org/sam/sam-model/

       is the ISO standard for the high-level model for Topic Maps.

   TMDM Concepts
       TMDM's main concepts are the

       topic map item
           containing any number of topic and association items

       topic item
           containing any number of names, occurrence items, subject locators and subject
           identifiers

       association item
           containing a type, a scope and any number of role items

       name item
           containing a string, a type and a scope

       occurrence item
           containing a data value (together with its data type), a type and a scope

       role item
           containing a type and a player

       All items have an item id and all (except the map) have a parent which links back to where
       the item belongs.

       This package implements for each of the above a class and access methods to retrieve
       actual structure and values from an existing map. Nota bene, there are some deviations
       from TMDM:

       •   only ONE identifier per item is supported

       •   at most ONE subject locator per topic is supported

       •   no variants are supported (might be added at some stage, poke me)

       •   a scope consists only of a single topic

       •   role items do not have an identity, so they also cannot be reified

   Modus Operandi
       Before you can use the TMDM layer, you need TM information in the form of a TM object. Any
       subclass should do, materialized and non-materialized maps should both be fine. Only with
       such a map you can instantiate a TMDM layer:

         use TM::Materialized::AsTMa;
         my $tm = new TM::Materialized::AsTMa (file => 'test.atm');

         use TM::DM;
         my $tmdm = new TM::DM (map => $tm);

       Probably the first thing you need to do is to get a handle on the whole topic map:

         my $topicmap = $tmdm->topicmap;

       That is delivered as an instance of TM::DM::TopicMap as described below. From there you
       start to extract topics and associations and that way you then further drill down.

   Implementation Notes
       This implementation only supports reading map information, not changing it or modifying
       the structure of the map. Not that it is impossible to do, but many applications get their
       map content from elsewhere and a read/write interface is an overkill in these cases.

       All objects generated here are ephemeral, i.e. they are only instantiated because you
       wanted the map information embedded into them. This implies that if you ask for one and
       the same topic twice, you are getting two copies of the topic information. The following
       will not work as expected:

          my $t0 = $topicmap->topic ('adam');
          my $t1 = $topicmap->topic ('adam');

          warn "have the same topic!" if $t0 == $t1;

       This will work:

          warn "have the same topic!" if $t0->id eq $t1->id;

INTERFACES

TM::DM
The TM::DM class itself does not offer much functionality itself. It only keeps the
connection to the background map.

Constructor

The constructor expects exactly one parameter, namely the background map.

$tmdm = new TM::DM (map => $tm)

Methods

topicmap
$topicmap = $tmdm->topicmap

This method generates a Topic Map item. See TM::DM::TopicMap .

TM::DM::TopicMap
This class provides access to all TMDM properties:

id This returns the item identifier.

topics
@topics = $topicmap->topics (@list-of-ids)

@topics = $topicmap->topics

@topics = $topicmap->topics ($selection-spec)

This method expects a list containing topic valid identifiers and returns for each of
the topics a "TM::DM::Topic" reference. If any of the input identifiers do not denote
a valid topic in the map, undef will be returned in its place. If the parameter list
is empty, all topics will be returned. Have fun, I mean, use with care.

Examples:

# round tripping topic ids
print map { $_->id } $topicmap->topics ('abel', 'cain' );

print "he again" if $topicmap->topics ('god');

If a selection is specified then the same language as in TM (method "toplets") can be
used.

associations
@as = $topicmap->associations

@as = $topicmap->associations (%search_spec);

This method retrieves the list of ALL associations when it is invoked without a search
specification. See TM for that.

reifier
This returns the topic item which reifies the association. "undef" is returned if
there is none.

topic
This returns a topic item with that id. This method will die if the id is invalid.
Note that always new copies are made.

TM::DM::Topic
subjectLocators
Returns the (only) subject locator (URI string) in the topic item or "undef" if there
is none.

subjectIdentifiers
Returns a list of URI strings. Might be empty.

id Returns the item id.

parent
Returns a TM::DM::TopicMap item in which this topic is embedded.

names
@names = $topic->names

Returns a list of TMDM name items.

occurrences
@occurrences = $topic->occurrences

Returns a list of TMDM occurrences items.

roles
@roles = $topic->roles

Returns a list of TM::DM::Role items where this topic plays any role.

TM::DM::Association
id Returns the item id.

type
Returns a TM::DM::Topic item which is the type of the association. This is always
defined.

scope
Returns the scope of the association in the form of a single TM::DM::Topic item. This
is always defined as for the unconstrained scope the topic "us" is used (see TM::PSI).

roles
@roles = $assoc->roles

Returns a list of roles of the association. Each role is a TM::DM::Role item.

parent
Returns a TM::DM::TopicMap item for the embedding map.

reifier
Returns a TM::DM::Topic item if this association is reified. "undef" otherwise.

TM::DM::Occurrence
id Returns the item id.

value
Returns the value (together with the data type) in the form of a TM::Literal object.

type
Returns a TM::DM::Topic item which is the type of the occurrence. This is always
defined.

scope
Returns the scope of the occurrence in the form of a single TM::DM::Topic item. This
is always defined.

reifier
Returns a TM::DM::Topic item if this occurrence is reified. "undef" otherwise.

parent
Returns the TM::DM::Topic item of the topic where this occurrence is part of.

TM::DM::Name
id Returns the item id.

value
Returns the string value of the name.

type
Returns a TM::DM::Topic item which is the type of the name. This is always defined.

scope
Returns the scope of the name in the form of a single TM::DM::Topic item. This is
always defined.

reifier
Returns a TM::DM::Topic item if this name is reified. "undef" otherwise.

parent
Returns the TM::DM::Topic item of the topic where this name is part of.

TM::DM::Role
player
Returns a TM::DM::Topic item for the topic which is the player in this role.

type
Returns a TM::DM::Topic item for the topic which is the type of this role.

parent
Returns a TM::DM::Association item of the association where this role is in.

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