---
title: RDF
TARGET DECK: Obsidian::STEM
FILE TAGS: data_model::rdf
tags:
  - data_model
  - rdf
---

## Overview

The **Resource Description Framework** (RDF) is the foundational representation language of the Semantic Web. The basic building block of RDF is the **triple** containing a **subject**, **predicate**, and **object**. Global identifiers of resources are represented as [[uri|URIs]] (or, more generally, IRIs). These URIs can be expressed more compactly as [[uri#CURIEs|CURIEs]].

A **graph** is a set of triples. A **named graph** is a particular set of triples with an associated name. When using named graphs, the term **quads** is often used in favor of triples. This refers to the original triple along with the name of the graph the triple is associated with.

%%ANKI
Basic
Which organization standardized RDF?
Back: W3C
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722340624977-->
END%%

%%ANKI
Basic
What is W3C an acronym for?
Back: **W**orld **W**ide **W**eb **C**onsortium.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722340624982-->
END%%

%%ANKI
Basic
What is RDF an acronym for?
Back: **R**esource **D**escription **F**ramework.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722187893324-->
END%%

%%ANKI
Basic
What is considered the basic representation language of the Semantic Web?
Back: RDF.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722187893326-->
END%%

%%ANKI
Cloze
With respect to RDF, a {resource} is {anything representable on the web}.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722187893328-->
END%%

%%ANKI
Basic
What aggregate concept is considered the basic building block of RDF?
Back: The triple.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722187893330-->
END%%

%%ANKI
Basic
What three components make up an RDF triple?
Back: The subject, predicate, and object.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722187893332-->
END%%

%%ANKI
Cloze
In RDF, a triple is a ({subject}, {predicate}, {object}) tuple.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722187893333-->
END%%

%%ANKI
Cloze
A {subject} is to a semantic triple as a row number is to a relation record.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722187893334-->
END%%

%%ANKI
Cloze
A {predicate} is to a semantic triple as an attribute is to a relation record.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722187893335-->
END%%

%%ANKI
Cloze
An {object} is to a semantic triple as a value is to a relation record.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722187893337-->
END%%

%%ANKI
Basic
Consider converting the following table to a triple. What is the subject?
![[triple-table-repr.png]]
Back: Row 2
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722188525589-->
END%%

%%ANKI
Basic
Consider converting the following table to a triple. What is the object?
![[triple-table-repr.png]]
Back: Hamlet
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722188525594-->
END%%

%%ANKI
Basic
Consider converting the following table to a triple. What is the predicate?
![[triple-table-repr.png]]
Back: Title
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722188525598-->
END%%

%%ANKI
Basic
RDF identifiers use what encoding?
Back: IRIs.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1722191359882-->
END%%

%%ANKI
Basic
How does RDF define a graph?
Back: As a set of triples.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1734804443458-->
END%%

%%ANKI
Basic
How does RDF define a named graph?
Back: As a graph (a set of triples) with a name.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1734804443462-->
END%%

%%ANKI
Cloze
{1:Triples} are to {2:graphs} whereas {2:quads} are to {1:named graphs}.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1734804443465-->
END%%

%%ANKI
Basic
What name is given to the members of a triple?
Back: "Subject", "predicate", and "object".
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1734804443466-->
END%%

%%ANKI
Basic
What name is given to the members of a quad?
Back: "Subject", "predicate", "object", and "graph".
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1734804443468-->
END%%

The RDF data model was designed from the beginning with [[federation|data federation]] in mind. Because every RDF store represents RDF data in the same way (i.e. as a set of triples), federation is as simple as combining the commonly encoded data into a single store before querying.

%%ANKI
Basic
What mechanism makes RDF data federation easy?
Back: Every source communicates data in the same way (i.e. as a set of triples).
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
Tags: data_model::federation
<!--ID: 1735176997772-->
END%%

%%ANKI
Basic
In the context of RDF, what does federation refer to?
Back: The combining of multiple RDF stores into a single (possibly virtual) view.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
Tags: data_model::federation
<!--ID: 1735176997776-->
END%%

%%ANKI
Basic
What does the federated graph refer to?
Back: The graph produced by combining various federated data sources.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
Tags: data_model::federation
<!--ID: 1735176997779-->
END%%

## Blank Nodes

A **blank node** (bnode) is a node in an RDF graph representing a resource for which a [[uri|IRI]] is not specified. That is, the represented resource is anonymous. Such a node can only be used as a subject or object in an RDF triple.

%%ANKI
Basic
What is a blank node?
Back: A node in an RDF graph representing a resource with an unspecified IRI.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735162429073-->
END%%

%%ANKI
Cloze
A {bnode} is shorthand for a {blank node}.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735162429077-->
END%%

%%ANKI
Basic
Which quantifier does a bnode correspond to?
Back: $\exists$
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735162429079-->
END%%

%%ANKI
Basic
What name is given to a node with an unspecified URI?
Back: A blank node.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735162429089-->
END%%

%%ANKI
Basic
What "position" in an RDF triple can a blank node take on?
Back: Either the subject or object.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735162429097-->
END%%

%%ANKI
Basic
What "position" in an RDF triple is a blank node prohibited to take on?
Back: The predicate.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735162429102-->
END%%

## Serializations

The original syntax and standard for writing RDF was RDF/XML. Turtle is an alternative, more human-readable, syntax. Besides these two exist many others.

%%ANKI
Basic
Which RDF serialization is most widely used?
Back: Turtle.
Reference: “Resource Description Framework,” in _Wikipedia_, November 25, 2024, [https://en.wikipedia.org/w/index.php?title=Resource_Description_Framework](https://en.wikipedia.org/w/index.php?title=Resource_Description_Framework&oldid=1259544587).
<!--ID: 1735507470222-->
END%%

%%ANKI
Basic
Why is Turtle named the way it is?
Back: It is an "acronym" for **Te**rse **R**DF **T**riple **L**anguag**e**.
Reference: “Resource Description Framework,” in _Wikipedia_, November 25, 2024, [https://en.wikipedia.org/w/index.php?title=Resource_Description_Framework](https://en.wikipedia.org/w/index.php?title=Resource_Description_Framework&oldid=1259544587).
<!--ID: 1735507470227-->
END%%

%%ANKI
Basic
What is RDF/XML a container for?
Back: RDF data.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470230-->
END%%

%%ANKI
Basic
What is Turtle a container for?
Back: RDF data.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470233-->
END%%

%%ANKI
Cloze
RDF is a {data model} whereas XML is a {serialization format}.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
Tags: serialization::xml
<!--ID: 1734805690321-->
END%%

%%ANKI
Cloze
RDF is a {data model} whereas Turtle is a {serialization format}.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470236-->
END%%

%%ANKI
Basic
How might RDF and XML relate to one another?
Back: XML can be used to serialize RDF.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
Tags: serialization::xml
<!--ID: 1734805690328-->
END%%

## SPARQL

SPARQL (SPARQL Protocol and RDF Query Language) is the standard way to access RDF data using a query language. Query patterns are represented in a variant of Turtle, the most ubiquitous language used to express RDF itself.

A server for the SPARQL protocol is called a **SPARQL endpoint**. It accepts SPARQL queries and returns results, according to the details of the protocol.

%%ANKI
Basic
SPARQL syntax most closely resembles which RDF serialization format?
Back: Turtle.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470239-->
END%%

%%ANKI
Basic
What is the standard means of querying an RDF store?
Back: SPARQL.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735506488320-->
END%%

%%ANKI
Basic
What is SPARQL an acronym for?
Back: **S**PARQL **P**rotocol **a**nd **R**DF **Q**uery **L**anguage.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735506488325-->
END%%

%%ANKI
Cloze
{1:SPARQL} is to {2:RDF} as {2:SQL} is to {1:RDBMS}.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735506488332-->
END%%

%%ANKI
Basic
The following snippet is an example of what language?
```sparql
SELECT ?movie WHERE {:JamesDean :playedIn ?movie}
```
Back: SPARQL
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735506488335-->
END%%

%%ANKI
Basic
What do the `:`s indicate in the following query?
```sparql
SELECT ?movie WHERE {:JamesDean :playedIn ?movie}
```
Back: The default namespace.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735506488338-->
END%%

%%ANKI
Basic
How are namespaces introduced in a SPARQL query?
Back: With the `:` character.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470242-->
END%%

%%ANKI
Basic
What do the `?`s indicate in the following query?
```sparql
SELECT ?movie WHERE {:JamesDean :playedIn ?movie}
```
Back: Variables to be matched against.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735506488341-->
END%%

%%ANKI
Basic
How are variables introduced in a SPARQL query?
Back: With the `?` character.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470245-->
END%%

%%ANKI
Basic
What do the curly braces (`{}`) indicate in the following query?
```sparql
SELECT ?movie WHERE {:JamesDean :playedIn ?movie}
```
Back: A graph pattern.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735506488344-->
END%%

%%ANKI
Basic
How are graph patterns introduced in a SPARQL query?
Back: With the `{` and `}` characters.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470248-->
END%%

%%ANKI
Basic
In SPARQL, what is a graph pattern?
Back: A graph with wildcards, used to match against a data graph.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735521898594-->
END%%

%%ANKI
Cloze
A {server for the SPARQL protocol} is called a {SPARQL endpoint}.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470252-->
END%%

%%ANKI
Basic
What is a SPARQL endpoint?
Back: A server that can respond to SPARQL queries.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470256-->
END%%

%%ANKI
Basic
What does Allemang et al. describe as the most web-friendly way to provide access to RDF data?
Back: Exposing a SPARQL endpoint to the data.
Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
<!--ID: 1735507470259-->
END%%

## Bibliography

* Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020.
* “Resource Description Framework,” in _Wikipedia_, November 25, 2024, [https://en.wikipedia.org/w/index.php?title=Resource_Description_Framework](https://en.wikipedia.org/w/index.php?title=Resource_Description_Framework&oldid=1259544587).