---
name: "XTM::topic"
section: "3pm"
platform: "linux"
package: "libxtm-perl"
version: "0.37-1"
release: "Debian 4.0 (Etch)"
platforms: ["linux"]
url: "https://new.carta.tech/XTM::topic"
---

# XTM::topic(3pm)

XTM::topic - Topic Map management, Topic

```
  use XTM::topic;
```

```
  my $t = new XTM::topic;
  ...
  print join (",", @{$t->occurrences()});
  print "bliss and happiness" if $t->has_instanceOf ('t-billionair');
```

```
  # now this time I am providing the id myself
  my $t2 = new XTM::topic (id => '1234');
```

```
  # there is also a cheap way to populate the topic with a default
  my $t3 = new XTM::topic (id => '1234', populate => \&XTM::topic::default_populate);
```

```
  # see XTM::generic for more methods
```

This package provides the primitive class Topic for Topic Maps.\
 **Constructor** The constructor expects a hash with following (optional) fields: a topic id (unique in the map in use), if not given, it will be generated a code reference to a subroutine populating the topic. There are the following **predefined** subroutines: This routine expects as first parameter a `"XTM::topic"`-blessed object and fills in the PSI topic as 'instanceOf', global scope where appropriate. It also generates in a fairly ad-hoc manner a 'baseName' from the topic id (substituting '-' by ' ').

```
  $t = new XTM::topic ('id' => 'x123');
```

**Methods** Following accessor methods are available via XTM::generic (see that package how to set/add values): @{ *$t*-\>baseNames}

returns list reference of XTM::baseName nodes. @{ *$t*-\>instanceOfs}

returns list reference of XTM::instanceOf nodes. *$t*-\>subjectIdentity

returns a XTM::subjectIdentity node Other methods are: print *$t*-\>id

*$t*-\>id ("x123");

returns the id of the topic. If provided with a non-empty scalar parameter, this value will be used to change the id. @{ *$t*-\>occurrences }

*$t*-\>occurrences ( *$coderef* )

*$t*-\>occurrences ( *$arrayref* )

returns the occurrences of the topic as a list reference. If provided with a CODEREF parameter, this subroutine will be used to filter the occurrences. If provided with a ARRAYREF parameter, this will be used as new value. *$t*-\>map

*$t*-\>map ( *$newmap* )

is an accessor method for the `"map"` component. *$t*-\>has\_instanceOf ( *$type\_topic\_id* )

returns true if the topic is a **direct** subtype of a topic specified as `"tid"` for the only parameter.

Example:

```
   print "bliss and happiness" if $t->has_instanceOf ('t-billionair');
```

*$t*-\>add\_defaults

This methods add default values according to the XTM standard. Specifically, it assures that *$t*-\>canonicalize

This method simplifies the topic by eliminating duplicates as prescribed in F.6. @{ *$t*-\>connected }

returns a list reference of all topic references mentioned in this topic. These references might be 'internal' or 'external' ones.

Example:

```
   foreach (@{$t->connected}) {
     print "$t->id mentions $_\n";
   }
```

*$t*-\>xml ( *$xmlwriter* )

returns an XML representation of the topic.

Example:\
    `$xmlwriter` = new XML::Writer ...\
    ...\
    `$t`-\>xml($xmlwriter); # outputs all onto `$xmlwriter` XTM, XTM::generic Copyright 200\[1-2\], Robert Barta \<rho@telecoma.net\>, All rights reserved. This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. http://www.perl.com/perl/misc/Artistic.html