1. ELIS – Multimedia Lab
RESTdesc
Efficient runtime service
discovery and consumption.
Ruben Verborgh, Thomas Steiner,
Davy Van Deursen, Rik Van de Walle, Joaquim Gabarró Vallés

2. ELIS – Multimedia Lab
Talking with others is difficult
when you’re different.
RESTdesc
© Jule Berlin Efficient runtime service discovery and consumption. 2

3. ELIS – Multimedia Lab
The goal is not
RESTdesc
to blend in…
© Eric Vest Efficient runtime service discovery and consumption. 3

4. ELIS – Multimedia Lab
…but to
stand out.
RESTdesc
© Nicholas Kreidberg Efficient runtime service discovery and consumption. 4

5. What makes a Web service
stand out from others?
Functionality.

6. Capturing functionality
is vital for automated
service consumption.

7. ELIS – Multimedia Lab
RESTdesc
Efficient runtime service
discovery and consumption.
1. Why? – need and challenges
2. What? – syntax and structure
3. So what? – benefits and potential
RESTdesc
Efficient runtime service discovery and consumption. 7

8. ELIS – Multimedia Lab
RESTdesc
Efficient runtime service
discovery and consumption.
1. Why? – need and challenges
2. What? – syntax and structure
3. So what? – benefits and potential
RESTdesc
Efficient runtime service discovery and consumption. 8

9. ELIS – Multimedia Lab
Example service: calculating photo height
768
photo height service
send a photo, retrieve its height in pixels
RESTdesc
Efficient runtime service discovery and consumption. 9

10. ELIS – Multimedia Lab
Several service description methods exist.
FACT: there are already lots of ways to describe that
• the input is an image;
• the output is a height in pixels.
FACT: none of them really helps... wait?
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11. ELIS – Multimedia Lab
They don’t describe functionality.
53 768 23.489
What height in pixels?
• The height of the face rectangle in the image?
• The optimal height on a certain mobile device?
• The height of the costume, mysteriously converted to pixels?
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12. ELIS – Multimedia Lab
Functional descriptions tell the whole story.
768
What height in pixels?
Only the functional relation tells us this:
send a photo, retrieve its height in pixels
RESTdesc
Efficient runtime service discovery and consumption. 12

13. ELIS – Multimedia Lab
RESTdesc
Efficient runtime service
discovery and consumption.
1. Why? – need and challenges
2. What? – syntax and structure
3. So what? – benefits and potential
RESTdesc
Efficient runtime service discovery and consumption. 13

14. ELIS – Multimedia Lab
Ingredients of RESTdesc
• HTTP
• resources
RESTdesc
Efficient runtime service discovery and consumption. 14

15. ELIS – Multimedia Lab
REST-style HTTP is resource-oriented.
http://example.com/images/wolfie
This is a resource.
http://example.com/images/wolfie/height
This is a resource, too.
They’re even the same resources
768 as those on the Semantic Web:
“Resource Description Framework”.
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16. ELIS – Multimedia Lab
Ingredients of RESTdesc
• HTTP
• resources
• Notation3 (N3)
• small superset of RDF
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17. ELIS – Multimedia Lab
Everything in RDF has 3 parts.
:MyPhoto :a :Photo.
subject verb object
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18. ELIS – Multimedia Lab
RDF is organized in vocabularies.
@prefix : <http://example.org/photo/>.
@prefix rdf: <http://www.w3.org/1999/02/22-­‐rdf-­‐syntax-­‐ns#>.
@prefix dbpedia: <http://dbpedia.org/resource/>.
:MyPhoto rdf:type dbpedia:Photo.
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19. ELIS – Multimedia Lab
Ingredients of RESTdesc
• HTTP
• resources
• Notation3 (N3)
• small superset of RDF
• your own vocabulary
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20. ELIS – Multimedia Lab
How do we describe this functionality?
768
photo height service
send a photo, retrieve its height in pixels
RESTdesc
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21. ELIS – Multimedia Lab
Photo height service in RESTdesc
@prefix : <http://restdesc.no.de/ontlogies/photos#>.
@prefix http: <http://www.w3.org/2006/http#>.
@prefix tmpl: <http://purl.org/restdesc/http-­‐template#>.
{ Not a new model.
?photo :photoId ?id. This is RDF in Notation3,
} a Semantic Web language.
=>
{
_:request http:methodName "GET";
tmpl:requestURI ("/photos/" ?id "/height");
http:resp [ tmpl:represents ?pixels ].
?photo :height ?pixels.
}.
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22. ELIS – Multimedia Lab
Photo height service in RESTdesc
If your photo
has identifier “wolfie”...
{ “wolfie
”
?photo :photoId ?id.
}
=>
{
_:request http:methodName "GET";
tmpl:requestURI ("/photos/" ?id "/height");
http:resp [ tmpl:represents ?pixels ].
?photo :height ?pixels.
}.
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23. ELIS – Multimedia Lab
Photo height service in RESTdesc
... then ...
{
?photo :photoId ?id.
}
=>
{
_:request http:methodName "GET";
tmpl:requestURI ("/photos/" ?id "/height");
http:resp [ tmpl:represents ?pixels ].
?photo :height ?pixels.
}.
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24. ELIS – Multimedia Lab
Photo height service in RESTdesc
...you can use HTTP to get
/photos/wolfie/height...
{
?photo :photoId ?id.
}
=>
{
_:request http:methodName "GET";
tmpl:requestURI ("/photos/" ?id "/height");
http:resp [ tmpl:represents ?pixels ].
?photo :height ?pixels.
}.
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25. ELIS – Multimedia Lab
Photo height service in RESTdesc
...and the response will 768
represent a value...
{
?photo :photoId ?id.
}
=>
{
_:request http:methodName "GET";
tmpl:requestURI ("/photos/" ?id "/height");
http:resp [ tmpl:represents ?pixels ].
?photo :height ?pixels.
}.
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26. ELIS – Multimedia Lab
Photo height service in RESTdesc
...which is 768
that photo’s height.
{ “wolfie
”
?photo :photoId ?id.
}
=>
{
_:request http:methodName "GET";
tmpl:requestURI ("/photos/" ?id "/height");
http:resp [ tmpl:represents ?pixels ].
?photo :height ?pixels.
}.
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27. ELIS – Multimedia Lab
This description contains everything you need.
768
“wolfie”
“wolfie
”
{
?photo :photoId ?id. It’s that simple.
}
And it’s that powerful.
=>
{
_:request http:methodName "GET";
tmpl:requestURI ("/photos/" ?id "/height");
http:resp [ tmpl:represents ?pixels ].
?photo :height ?pixels.
}.
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28. ELIS – Multimedia Lab
RESTdesc
Efficient runtime service
discovery and consumption.
1. Why? – need and challenges
2. What? – syntax and structure
3. So what? – benefits and potential
RESTdesc
Efficient runtime service discovery and consumption. 28

29. ELIS – Multimedia Lab
RESTdesc descriptions are simple, because…
They rely on HTTP and HTTP best practices.
• resource-oriented
They use the vocabulary you choose.
• descriptions adapts to your domain
They describe only what you need.
• concepts live in vocabularies
• “height” is an integer, expresses a length in pixels
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30. ELIS – Multimedia Lab
RESTdesc descriptions are powerful, because…
They use the Resource Description Framework.
• logically sound
• allows complex expressions
• interoperable with other services and data
They can be composed by generic reasoners.
• all N3 reasoners understand RESTdesc
• enables goal-driven service composition
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31. RESTdesc enables
straightforward
automated use of services.

32. Seeing services as resources
leads to elegant
functional descriptions.

33. In functional descriptions,
services are not defined
by what they look like…

34. ELIS – Multimedia Lab
…but by
what they do.
http://restdesc.org/
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