What do "IS" "IL" and "IEXT" refer to in the RDF Semantics specification?

3
votes

These terms are used in the "Definition of a simple interpretation" table on http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#interp . I am a little unclear on their meaning.

At this point I think they mean, Intermediate Language,

I am a little unclear on the meaning of these abbreviations. I am guessing that they mean Intermediate Language, Intermediate System, and Intermediate Extension (or any of these, substituting "interpretation" for "intermediate"). This information isn't explicit in the documentation, and I don't have enough context to know conclusively what is being referred to.

Edit I copied the section where it is used below:

Definition of a simple interpretation.

A simple interpretation I of a vocabulary V is defined by:

1. A non-empty set IR of resources, called the domain or universe of I.

2. A set IP, called the set of properties of I.

3. A mapping IEXT from IP into the powerset of IR x IR i.e. the set 
   of sets of pairs <x,y> with x and y in IR .

4. A mapping IS from URI references in V into (IR union IP)

5. A mapping IL from typed literals in V into IR.

6. A distinguished subset LV of IR, called the set of literal values, 
   which contains all the plain literals in V
2
rdfdefinitioninterpreted-language

2 Answers

4
votes

It is a little inscrutable, unless you're used to formal logic.

An interpretation is a particular understanding of a set of statements in some artificial language (in this case RDF). It sounds grand, but it's typically so obvious you don't even think about it. For example :a :p :b . might have an interpretation ':a is Anne, :b is Bob, and :p is lives-next-to'. Armed with that mapping between terms and things you can interpret :a :p :b. Many other interpretations are possible.

RDF simple interpretations are just such a mapping (actually, a set of mappings). They each have terse labels.

  1. IR (Interpretation Resources), a set of all the things we can talk about (Anne, Bob, clouds etc.).
  2. IP (Interpretation Property), a set of all the properties we can talk about (love, lives-next-door-to etc).
  3. IEXT (Interpretation Extension). Explains what the extension of a property is. Informally the extension of a property P is all the pairs of things for which the property hold. So even if you don't understand 'blarg' you can work out whether :a :blarg :b by just looking for <:a, :b> in the extension of :blarg. The definition given is a formalised version of this: you map properties into the set of all pairs of resources.
  4. IS (Interpretation Subjects). Assigns URIs to all things which might appear in the subject position (resources and properties). (V is the vocabulary -- the terms -- of the language).
  5. IL (Interpretation Literal). Maps typed literal terms to things.
4
votes

The definitions are given in the quoted text you pasted. e.g. "5. A mapping IL from typed literals in V into IR." defines IL.

IL is defined as a mathematical map function. The key of the map (from): literals in V. The value of the map (to): IR

and so on for IS and IEXT