Slides of my presentation at WWW 2012 PhD Symposium

1. Binary RDF for Scalable Publishing,
Exchanging and Consumption
in the Web of Data
Javier D. Fernández
Supervised by: Miguel A. Martínez-Prieto and Claudio Gutierrez
University of Valladolid (Spain)
University of Chile (Chile)
PhD Symposium

2. Brief RDF Introduction
(1) Resource Description Framework
 Webs, services, protocols
 Persons, Proteins, geography…
(2) A standard model for data exchange on the Web
 Understandable by computers
(3) W3C Recommendation (2004)
(4) Data model
 (subject, predicate, object)
PhD Symposium

3. RDF Example
literal
Subject, Predicate, Object
(U,B) , U , (U,B,L)
“Pablo Neruda”
URI
URI URI
<http://books/author33>
<http://books/book21>
“Spain in the Heart”
_collection <http://myblog/lectures>
lectures:to_read_list
Blank
PhD Symposium

4. 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 the standards (RDF*, SPARQL)
4. Include links to other URIs, so that they can discover more things.
Image:PhD Symposium
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5. Image:PhD Symposium
Danilo Rizzuti / FreeDigitalPhotos.net

6. Scalability problems
DBPedia (en) 233 M.triples ~ 33 GB
Uniprot 845 “ ~ 230 GB
 Publish?
 Exchange?
 Process/Consume/Query?
PhD Symposium

7. RDF Publication
dereferenceable URIs
RDF dump
sensor
SPARQL Endpoints/
APIs
 No Recommendations/methodology to publish at large scale
 Related Work: Some metadata for discovery, such as Void, Semantic
Sitemaps.
PhD Symposium

8. RDF Exchanging issues
 RDF/XML, N3, Turtle, JSON.
 Document-centric (verbose)  data-centric view (machine)
 No structure (chunks, universal compression)
 Related Work: Universal compression (gzip, bzip2) and the Efficient XML
Interchange Format (EXI).
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renjith Symposium

9. RDF Processing/Consumption (After Exchanging)
 Costly Post-processing
 Decompression
 Indexing (RDF Store)
 Finally… consume
 Related Work (indexing): Based on Relational Storage (Virtuoso) Multi-indexes
(RDF3X), Distributed Systems (Map-Reduce) and others (Bit-Mat).
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renjith Symposium

10. The scalability problems has
a main impact on Users
Would you download hundreds of GB...
… if you don’t know exactly what they contain,
that need costly exchange and post-processing,
and require a powerful store to query them ?
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renjith Symposium

11. In the following...
1. Proposed approach for scalable publishing, exchanging and consumption
of large RDF datasets
2. Preliminary results
3. Methodology
4. On-going work and conclusions
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12. An integrated solution
We call for, and we study in this thesis, a Binary RDF Serialization format:
 Machine oriented (binary)
 Clean publication
 Metadata
 Modular
 Efficient exchange
 Compression
 Basic data operations
 Easy to parse and consume
 Primitive query resolution
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13. HDT Overview
PhD Symposium

14. Dictionary+Triples partition
1 <http://books/author33>
2 <http://books/book21> 6
3 dc:author
4 dc:title
5 foaf:name 1
2
6 “Pablo Neruda”
7 “Spain in the Heart” 7
PhD Symposium

15. Key concepts: The Dictionary
 Largest component (up to 74%)
 Long URIs, shared prefixes
 Lang, datatype tags in literals
 Efficient IDString operations
We plan to work on a specific organization which
 Optimizes space (regularities)
 Provides efficient performance in operations
PhD Symposium

16. Preliminary results in Rich Functional Dictionaries
We propose to adapt techniques for string dictionaries;
 Front-Coding
 Making dictionary partitions
[*] Compression of RDF Dictionaries. Miguel A. Martínez-Prieto, Javier D. Fernández,
Rodrigo Cánovas. ACM Symposium on Applied Computing (SAC 2012).
PhD Symposium

17. Key concepts: Triples
 Specific compression:
 More efficient compression than just gzip.
 Data indexing for consumption:
 Allows direct patterns resolution without decompression
(s,p,o), (s,?p,?o) and (s,p,?o)
We plan to work on a specific technique which
 optimizes space
 provides efficient performance in primitive operations
PhD Symposium

18. Preliminary results in Triples Encoding
We propose to use Bitmap indexes:
[*] Compact Representation of Large RDF Data Sets for Publishing and
Exchange. Javier D. Fernández, Miguel A. Martínez-Prieto, Claudio Gutierrez.
International Semantic Web Conference(ISWC 2010).
PhD Symposium

19. Methodology
 RDF structure in theory and practice.
 Binary RDF Specification.
 Succinct Dictionaries.
 Triples Indexes.
 Practical deployment.
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20. Some Results… HDT Acknowledged as W3C
member submission:
http://www.w3.org/Submission/2011/03/
supported by:
PhD Symposium

21. Some Results... HDT for exchanging
PhD Symposium

22. Some Results... HDT for consumption
Direct Consumption, without decompression after exchanging
 Example of use: HDT-it (Thanks to Mario Arias, DERI)
Image:PhD Symposium
jscreationzs / FreeDigitalPhotos.net

23. On-going promising work: HDT-FoQ
[*] Exchange and Consumption of Huge RDF Data. Miguel A. Martínez-Prieto,
Mario Arias, Javier D. Fernández. Extended Semantic Web Conference(ESWC
2012). To appear
PhD Symposium

24. In conclusion
Binary RDF aims to lightweight the Web of Data;
 Logical decomposition: Header, Dictionary, and Triples
 Clean publication
 Compressed RDF format for exchanging
 Machine-friendly, direct consumption
 Rich Functional Dictionary/Triples representations for querying
PhD Symposium

25. Still much work on…
 Getting a global understanding of the real structure of RDF networks.
 Applying this knowledge in innovative dictionary and triples indexes.
 full SPARQL at consumption
 Supporting dynamic operations
 inserting, deleting, and updating binary RDF
PhD Symposium

26. Thanks!
HDT: http://www.rdfhdt.org/
Group: http://dataweb.infor.uva.es/
Slides: http://www.slideshare.net/javifer
Javier D. Fernández (jfergar@infor.uva.es)
Supervised by: Miguel A. Martínez-Prieto, Claudio Gutierrez
University of Valladolid (Spain)
University of Chile (Chile)
PhD Symposium