Glossary

These are not formal definitions - just phrases to help you get the hang of what these things mean. The definition terms are linked back to more information where available.

Class

A set of Things; a one-parameter predicate; a unary relation.

DAML

Darpa Agent Markup Langauge. This is DARPA's name for the US govenment funded projects which led to, among other things, OWL. The DAML site has useful pointers and registries of useful ontologies and data in RDF.

domain

For a Property, a class of things which any subject of the Property must be in.

Formula

An (unordered) set of statements. You can write one out in N3 using {braces}.

context

The relationship between a statement and a formula containing it.

cwm

(From: Closed world machine; valley.) A bit of code for playing with this stuff, as grep is for regular expressions. Sucks in RDF in XML or N3, processes rules, and spits it out again.

existential variable

A term in a language (such as N3) which stands in place of a normal symbol, allowing one to consider a formula being true for some symbol being put consistently in place of the variable.

filter

A set of rules which are used to select certain data from a larger amount of information.

Formula

A set of statements, with a list of universally quanitified variables and a list of existentially quantified variables. In N3, a literal formula if representated by braces {}.

N3

Notation3, a quick notation for jotting down or reading RDF semantic web information, and experimenting with more advanced sematic web features.

object

Of the three parts of a statement, the object is one of the two things related by the predicate. Often, it is the value of some property, such as the color of a car. See also: subject, predicate.

OWL

The Web Ontology Language standard from W3C. Currently (2003/04) on the Recommensation track. An RDF vocabulary.

predicate

Of the three parts of a statement, the predicate, or verb, is the resource, specifically the Property, which defines what the statement means. See also: subject, object.

Property

A sort of relationship between two things; a binary relation. A Property can be used as the predicate in a statement.

range

For a Property, its range is a class which any object of that Property must be in.

rule

A loose term for a Statement that an engine has been programmed to process. Different engines have different sets of rules. cwm rules are statements whose verb is log:implies.

Resource

That identified by a Universal Resource Identifier (without a "#"). If the URI starts "http:", then the resource is some form of generic document.

Statement

A subject, predicate and object which assert meaning defined by the particular predicate used.

subject

Of the three parts of a statement, the subject is one of the two things related by the predicate. Often, it indicates the thing being described, such as a car whos color and length are being given. See also: object, predicate

Thing

In OWL, a generic name for anything - abstract, animate, inanimate, whatever. The class which anything is in. (In RDF parlance, confusingly, rdf:Resource.) Identified by a URI with or without a "#" in it. Tip: Saying something is a Thing doesn't tell anyone anything, which is why you don't see it much.

Truth

In the log: namespace, a Class of all formulae which are true.

type

A particular property used to assert that a thing is in a certain Class. The relationship between a thing and any Class it is in.

universal variable

A term in a language (such as N3) which stands in place of a normal symbol, allowing one to consider a formula being true for any symbol being put consistently in place of the variable.

URI

Universal Resource Identifier. The way of identifying anything (including Classes, Properties or individual things of any sort). Not everything has a URI, as you can talk about something by just using its properties. But using a URI allows other documents and systems to easily reuse your information.

variable

Either a universal variable or an existential variable.