SLD Revolution: A Cheaper, Faster yet more Accurate Streaming Linked Data Framework

Politecnico di Milano, DEIB
Portoroz - 2017 - Riccardo Tommasini - @rictomm - Politecnico di Milano
Marco Balduini, Riccardo Tommasini, Emanuele Della Valle
A Cheaper, Faster yet more Accurate  
Streaming Linked Data Framework
1

ESWC
RSP is Great!
2

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ESWC
Why RSP?
3
- offers a generic overview over streams and static data
- enables query answering across heterogeneous sources
- consents to create/publish new streams or graphs

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The RSP Idea
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in short

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CQL Model
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Streams
Relations
Streams-to-Relations
Relations-to-Streams
Relationsto-Relations
The CQL continuous query language  
- Arvind Arasu · Shivnath Babu · Jennifer Widom, 2006, VLDBJ

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ESWC
RSP-QL Model
6
RDF Streams Solution
Mappings
S2R operators
R2S operators
R2R operators
The CQL continuous query language  
- E. Della Valle, S. Ceri, D. Barbieri, D. Braga, A. Campi, 2008, FIS

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RSP in a Nutshell
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RDF Stream-to-RDF
RDF-to-RDF (solution mappings)
RDF-to-RDF Stream
on RDF Streams

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RSP in Practice
8
With SLD

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An Social Media Example
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How many micro-posts do occur over time?
How often does a hashtag appears in the micro-post
stream?
Two Information Needs

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ESWC
Streaming Linked Data Server
Sources
Raw Stream
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Adapter RDF Stream Bus Publisher
Visualizer
Recorder Re-player Analiser Decorator

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ESWC
11

An Important
Optimisation
REGISTER STREAM sstr AS
CONSTRUCT {
?id sma:twitterCount ?tc }
FROM STREAM <social> [RANGE 1m STEP 1m]
WHERE {
SELECT (uuid() AS ?id) ?tc
WHERE {
SELECT
(COUNT (DISTINCT ?mp) AS ?tc)
WHERE {
?mp a sma:Tweet } } }
12

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ESWC
13

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14

Using
C-SPARQL
REGISTER STREAM countT AS
CONSTRUCT {
?uid sma:twitterCount ?tot .}
FROM STREAM <sstr> [RANGE 15m
STEP 1m]
WHERE {
SELECT
(uuid() AS ?uid)
(SUM(?tc) AS ?tot)
WHERE {
?id sma:twitterCount ?tc }}
15

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Is RSP always great?
16

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Observations
17
It is flexible. :)
It forces RDF when query results are often relational :(
It is not optimal, i.e. RSP-QL vs SQL vs Path Queries
on SLD

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Revolutionising SLD
18

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A “Lazy” Processing Model
19
Stream operators can be applied on generic data items.
QL-specific operators requires a particular data type.
Postpone the data transformation as late as possible.
on streams

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Generic Programming
20
Generic programming is a style of computer
programming in which algorithms are written in terms of
types to-be-specified-later that are then instantiated
when needed for specific types provided as parameters.
an old idea

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A new Processing Model
21
Generic 
Streams<T>
Generic 
Instantaneous<T>
S2I<T>
I2S<T>
I2I<T>

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Lazy Transformation by Generic Programming
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stream-to-instantaneous<T>
instantaneous-to-instantaneous<T>
instantaneous-to-stream<T>
on streams<T>

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RSP in Practice
23
with SLD Revolution

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Sources
Stream
Sink
Streaming Linked Data Revolution Server
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Receiver Generic Stream Bus Translator
Stream
Recorder Re-player Processor Decorator

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ESWC
25

ESWC
SLD vs SLD Revolution
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Let’s be quantitative

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It is faster, cheaper yet more accurate than SLD.
27
R² = 0,96413R² = 0,99891
30
300
3000
1 10 100
Median Engine Memory (MB)
Median CPU Load (%)
SLD
SLD Revolution
Expon. (SLD)
Linear (SLD Revolution)

ESWC
Discussion & Conclusion
28

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Observations
29
It is faster, cheaper yet more accurate than SLD. :)
It requires to know EPL, SPARQL, JSON path queries. :(
It is optimised and, thus, not flexible. :(
on SLD Revolution

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Open Problems
30
RSP-QL is not always the best solution in terms of cost/performance
Can we identify an optimum?
Can we define a cost model for RSP-QL ?

Questions?
Email: riccardo.tommasini@polimi.it 
Twitter: @rictomm
31
Email: marco.balduini@polimi.it 
Twitter: @ balducci85
Pablo Picasso, Les Demoiselles d'Avignon, 1907.  
Museum of Modern Art (MoMA), New York City, NY, US

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