Week 2

Question 1

4 proposals for knowledge
graphs

Answer 1

1. Give all things a name
2. Names are addresses on the Web
3. Relations between things form Graphs of Data
4. Add explicit semantics (formal knowledge) to allow for
   predictable inferencing

Question 2

linked data

Answer 2

a set of best practices for publishing and connecting structured data on the web

is meant to create a more accessible data world where data is linked with each other ont he web

Question 3

open data

Answer 3

data that is freely available for anyone to access

Question 4

linked open data

Answer 4

making your data available in some common data formats like links and making your data useable and reusable

Question 5

model

Answer 5

a simplified representation of the real world, made for understanding, structuring, predicting and communicating

Question 6

four linked daya principles

Answer 6

1. Use URIs as names for things
2. use HTTP URIs so that people can look up those names
3. when someone looks up a URI, provide useful information using RDF
4. Include links to other URIs so that they can discover more things

Question 7

URI

Answer 7

Uniform Resource Identifier, resources are identified by URIs, cannot have the same ID for the same thing

Question 8

literals

Answer 8

used to represent ‘literal’ data values and always have a datatype. datatypes are also resources

Question 9

RDF graph

Answer 9

a set of triples that contains two triples

Question 10

why HTTP URIs

Answer 10

HTTP URIs have a global scope and are unique throughout the web.

this helps avoid name clashes and they’re grounded in society

Question 11

why triples?

Answer 11

any information format can be transformed to triples.

relations are made explicit, they are elements in their own right.
- unlike database columns and binary predicates
- the predicate is an element in a triple and can be described in RDF
- self-documenting

Question 12

why graphs?

Answer 12

• a single but highly versatile format
• since rdf graphs are sets of triples, basic set operations are well-defined
• take the union to merge two graphs
• extend a graph by adding more triples

Question 13

blank nodes

Answer 13

resources without a URI, when resource is unknown or has no identifier. can be either object or subject

Question 14

RDF

Answer 14

a generic language for describing data about resources written in forms of web enabled knowledge graphs

extends the linking structure of the web

completely application independent

Question 15

SPARQL

Answer 15

specifies how to query triple stores over HTTP, specifies syntax for writing queries, six types:
- SELECT
-CONSTRUCT
-INSERT
-DELETE
-ASK
-DESCRIBE