RDF

Question 1

What is Stardog’s data model?

Answer 1

A directed semantic graph

Question 2

What does RDF stand for and what does it mean?

Answer 2

Resource Description Framework, provides a standardized model for representing data and its meaning

Question 3

What does W3C stand for, and what’s its purpose?

Answer 3

World Wide Web Consortium, and they are the main international standards organization for the internet

Question 4

What is a directed graph?

Answer 4

A set of objects, called ‘nodes’, connected together by lines, called ‘edges’, that are ‘directed’ from one node to another

Question 5

What is the specific naming that RDF has for edges, source nodes, and target nodes?

Answer 5

Edge -> Predicate
Source node -> Subject
Target node -> Object
Image

Question 6

What is a triple composed of?

Answer 6

A subject, predicate, and object

Question 7

What is a class made up of?

Answer 7

A set of individuals (also known as instances or objects)

Question 8

What purpose do classes and objects serve in a triple?

Answer 8

They act as either the subject or the object

Question 9

What is the part of an RDF triple that connects the subject and object?

Answer 9

Predicate

Question 10

What are the two ways in which a predicate is used?

Answer 10

1. As an object property when it describes a relationship between two objects
2. As a data property when it provides data about an object

Question 11

What is a graph made up of?

Question 12

What is an RDF graph made up of?

Answer 12

Multiple connected RDF triples

Question 13

What are the three types of RDF nodes?

Answer 13

1. IRI - node with a unique identifier
2. Blank node - node without a unique identifier
3. Literal - node representing a literal value, like a number or date

Question 14

Shorten the IRI below with a prefix rdf and local name type
http://www.w3.org/1999/02/22-rdf-syntax-ns#type

Answer 14

Create a prefix that contains the ‘long ugly stuff’, minus the part you want as the local name. In this case the local name is type:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
Then you just use the prefix rdf, a colon, and the local name: rdf:type

Question 15

How are literals written?

Answer 15

They are written in quotes, followed by their datatype IRI:
"1963-03-22T21:44:00Z"^^xsd:dateTime

Question 16

Where can you store prefix declarations when using Stardog?

Answer 16

In the database metadata, which allows you to simplify your actual query to only shorthand syntax

Question 17

What is the shorthand for writing string objects?

Answer 17

Simply use quotes, i.e”
"The Beatles"^^xsd:string –> "The Beatles"

Question 18

What’s the shorthand for rdf:type?

Answer 18

a

Question 19

What are the purposes of ;, ,, and . in Turtle syntax?

Answer 19

; - separate statements about the same subject
, - list multiple objects for the same statement about a subject
. - end the string of statements about a subject

E.g:
~~~
:Love_Me_Do a :Song ;
:name “Love Me Do: ;
:length 125 ;
:writer :John_Lennon, :Paul_McCartney .
~~~

Question 20

What are blank nodes used for?

Answer 20

They are used to describe a pattern of relationships where a part of that pattern is undefined.

E.g, ‘Please Please Me’ is an album that has a track on side 2 #1 called ‘Love Me Do’
~~~
:Please_Please_Me :track _:s2n1 [
:side 2 ;
:order 1 ;
:song :Love_Me_Do ] .
~~~

Question 21

How are blank nodes written?

Answer 21

They start with _: and must have a unique name from all the other blank nodes in the Turtle document, e.g. _:s2n1