Turtle: triples

Turtle writes statements of three parts

Turtle looks different from X M L and JSON. It writes a record as a set of short statements. Each statement has three parts, and ends with a full stop.

A form, as Turtle

Here is the same made up person form. Turn it over, and this is Turtle. First, a prefix gives a short name to a long address. Then each line is a statement. It names the thing, the property, and the value, and ends with a full stop. The first says the person has a name. The second says the person was born on a date. Every fact is one statement of three parts.

Subject, predicate, object

The three parts have names. The subject is the thing the statement is about. The predicate is the property, or the relationship. And the object is the value, or the other thing. Together they make a triple, and a collection of triples makes a graph.

• Part 1 · Subject · What the statement is about. · person
• Part 2 · Predicate · The property or relationship. · link
• Part 3 · Object · The value, or another thing. · tag

Turtle's shortcuts

Turtle has shortcuts so you do not repeat yourself. A prefix directive gives a short name to a long address. A semicolon repeats the subject, so you can list several properties of the same thing. A comma repeats the subject and the property, so you can list several values. And the letter a, in the predicate place, means is a type of.

• @prefix · A short name for a long address · tag · navy
• Semicolon ; · Same subject, new property · link · navy
• Comma , · Same subject and property, new value · layers · amber
• The word a · Means: is a type of · check · slate

Exchange or knowledge

FHIR can write resources as an R D F graph in Turtle. The specification says the purpose is to bridge operational data exchange and formal knowledge processing. It is a fully working representation, but with different characteristics from JSON and X M L, and a trial use status. It says systems focused on operational exchange would not usually choose it.

Check yourself

Pause and think. What are the three parts of a Turtle triple? The answer: subject, predicate, and object.

• Subject, predicate and object
• Name, type and size
• Start, middle and end
• Key, lock and value

Keep these in mind

Turtle writes statements made of a subject, a predicate and an object. Each statement ends with a full stop. Prefixes, semicolons and commas save repeating. And FHIR offers Turtle as a bridge to knowledge systems.

• Turtle writes statements: subject, predicate, object
• Each statement ends with a full stop
• Prefixes, semicolons and commas save repeating
• FHIR offers Turtle as a bridge to knowledge systems