"WordNet is a semantic lexicon for the English language. It groups English words into sets of synonyms called synsets, provides short, general definitions, and records the various semantic relations between these synonym sets. The purpose is twofold: to produce a combination of dictionary and thesaurus that is more intuitively usable, and to support automatic text analysis and artificial intelligence applications.

WordNet distinguishes between nouns, verbs, adjectives and adverbs because they follow different grammatical rules. Every synset contains a group of synonymous words or collocations (a collocation is a sequence of words that go together to form a specific meaning, such as "car pool"); different senses of a word are in different synsets. The meaning of the synsets is further clarified with short defining glosses (Definitions and/or example sentences). A typical example synset with gloss is:

good, right, ripe -- (most suitable or right for a particular purpose; "a good time to plant tomatoes"; "the right time to act"; "the time is ripe for great sociological changes")

Most synsets are connected to other synsets via a number of semantic relations."

[source: http://en.wikipedia.org/wiki/WordNet]

Using JWNL is very simple. First, call JWNL.initialize() somewhere in the initialization code of your program. Then, just call Dictionary.getInstance() to get the currently installed dictionary. The only dictionary methods you should really ever need to call are lookupIndexWord(), lookupAllIndexWords(), and getIndexWordIterator().

The other methods you may be interested in Relationship.findRelationships(), and those in PointerUtils.

Relationship.findRelationships() allows you to find relationships of a given type between two words (such as ancestry). Another way of thinking of a relationship is as a path from the source synset to the target synset.

The methods in PointerUtils allow you to find chains of pointers of a given type. For example, calling PointerUtils.getHypernymTree() on the synset that contains "dog," returns a tree with all its parent synsets ("canine"), and its parents' parents ("carnivore"), etc., all the way to the root synset ("entity").

JWNL provides support for accessing the WordNet database through three structures - the standard file distribution, a database, or an in-memory map. Utilities are provided to convert from the file structure to an SQL database or in-memory map, and a configuration file controls which system the library uses.

A JWNL Properties file is an XML file that can be validated using the included DTD or XSD.

Basically, the properties file allows you to specify three properties:

- Dictionary class: This defines the class used to interface with the dictionary. JWNL comes with three dictionary classes - MapBackedDictionary, FileBackedDictionary, and DatabaseBackedDictionary. Exactly 1 dictionary tag is required in a properties file. If there are more than one, the first one will be used.

    <dictionary class="[dictionary class name]">
    ..parameters
    </dictionary>

  <version publisher="[publisher]" number="[version number]" language="[language]" country="[country]"/>

- Resources: A resource file contains mapping between keys and text used in the program. Typically, this text is error or status messages. Resource files are used so that a program can be used with different (spoken) languages without having to modify the code. See the Java documentation for java.util.ResourceBundle on how to name your resource files. You can specify as many resources as you want.

  <resource class="[resource file path]"/>

  <jwnl_properties language="en" country="us">
    ..properties
  </jwnl_properties>

You'll notice that dictionary and dictionary_element_factory allow you to provide parameters. Parameters are of the form:

  <param name="[param name]" value="[param value]">
    ..nested parameters
  </param>

  <param name="data_class" value="net.didion.stuff.Money">
    <param name="currency" value="USD"/>
  </param>

The valid parameters for each class are specified in that class's documentation. I would encourage you to follow this convention of documenting valid parameters in the class documentation of any classes you write that take parameters.