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What is the data redundancy in LD?
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Data Redundancy
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[Database systems] Same piece of data in multiple places
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[Information theory] Wasted "space" used to transmit certain data
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(In this work)Linked Data Redundancy
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Wasted “space” to represent certain meaning (represented in certain semantics)
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Duplication-free](https://image.slidesharecdn.com/redundancyanalysiscold2014rivadelgardar-141020143025-conversion-gate02/85/Redundancy-analysis-on-linked-data-cold2014-ISWC2014-3-320.jpg)
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RDF Redundancies vs. Succinct Representations
[Rule based] A. K. Joshi, P. Hitzler, and G. Dong. Logical linked data compression. In The Semantic Web: Semantics and Big Data, pages 170–184. Springer, 2013.
[HDT]J. D. FernáNdez, M. A. MartíNez-Prieto, C. GutiéRrez, A. Polleres, and M. Arias. Binary rdf representation for publication and exchange (hdt). Web Semant., 19:22–41, Mar. 2013.
[WaterFowl] O. Curé, G. Blin, D. Revuz, and D. C. Faye. Waterfowl: A compact, self-indexed and inference-enabled immutable rdf store. In The Semantic Web: Trends and Challenges, pages 302– 316. Springer, 2014.
Pan, Jeff Z., Jose Manuel Gomez-Perez, Yuan Ren, Honghan Wu, Haofen Wang and Man Zhu. “Graph Pattern based RDF Data Compression”. In Proc. of 4th Joint International Semantic Technology Conference (JIST). 2014. (To appear)](https://image.slidesharecdn.com/redundancyanalysiscold2014rivadelgardar-141020143025-conversion-gate02/85/Redundancy-analysis-on-linked-data-cold2014-ISWC2014-6-320.jpg)
Redundancy analysis on linked data #cold2014 #ISWC2014
- 1. How redundant is it? – An empirical analysis on linked datasets Honghan Wu1, Boris Villazon-Terrazas2, Jeff Z. Pan1 and José Manuel Gómez Pérez2 University of Aberdeen1, UK iSOCO2 , Spain 20/10/2014 1
- 2. 2 Content • What is data redundancy with linked data? • Why is it of special interest to linked data consumption? • Linked Data redundancy categorisation • How to analysis? • Dataset selection & The Result • Conclusion
- 3. 3 What is the data redundancy in LD? • Data Redundancy – [Database systems] Same piece of data in multiple places – [Information theory] Wasted "space" used to transmit certain data • (In this work)Linked Data Redundancy – Wasted “space” to represent certain meaning (represented in certain semantics) – Duplication-free
- 4. 4 Why is it of special interest to LD consumption? • Bad Redundancy & Good Redundancy – Bad for exchange: storage, transmission – Good for inference computation • Relevant consumption tasks – Hosting/Sharing – Query Answering (SPARQL) – Ontology Based Data Access – Reasoning
- 5. Redundancy in Linked Data • Redundancy Categorisation for RDF Data • Redundancies caused by the “Linked” nature
- 6. 6 RDF Redundancies vs. Succinct Representations [Rule based] A. K. Joshi, P. Hitzler, and G. Dong. Logical linked data compression. In The Semantic Web: Semantics and Big Data, pages 170–184. Springer, 2013. [HDT]J. D. FernáNdez, M. A. MartíNez-Prieto, C. GutiéRrez, A. Polleres, and M. Arias. Binary rdf representation for publication and exchange (hdt). Web Semant., 19:22–41, Mar. 2013. [WaterFowl] O. Curé, G. Blin, D. Revuz, and D. C. Faye. Waterfowl: A compact, self-indexed and inference-enabled immutable rdf store. In The Semantic Web: Trends and Challenges, pages 302– 316. Springer, 2014. Pan, Jeff Z., Jose Manuel Gomez-Perez, Yuan Ren, Honghan Wu, Haofen Wang and Man Zhu. “Graph Pattern based RDF Data Compression”. In Proc. of 4th Joint International Semantic Technology Conference (JIST). 2014. (To appear)
- 7. 7 Semantic redundancy Rule Representation - DL Axioms (T-Box) - Other semantics (graph pattern substitution)
- 8. 8 Syntactic Redundancy Concise syntax - RDF abbreviation & striping syntax - Intra-structure & Inter- structure
- 9. 9 Symbolic Redundancy • http://xmlns.com/foaf/0.1/name – 31 bytes in ASCII URI ID (4 bytes) … … http://xmlns.com/foaf/0.1/name 128 … … Less bytes for basic data units - (Fix-length)Dictionary Based - (Variable-length) Huffman coding - Predictive encoding
- 10. 10 Semantic Redundancy Caused by “Linked” Nature • Vocabulary Linkage – Reuse of other vocabularies: more rules – Less redundancy ratio: more triples derivable – More redundancy: co-occurrence triples removable • Instance Linkage – sameAs linkages – Bring in new assertions (e.g., type assertions) – Bring in new axioms
- 11. How to analysis? • Two dimension analysis • Methodology • Metrics
- 12. 12 Two dimension analysis Semantic Syntactic Symbolic A-Box ✔ ✔ A-Box & T-Box No Linkage ✔ - - T-Box Reuse ✔ - - A-Box Linkage - - RDF Redundancy Dimension Linked Semantic Dimension
- 13. 13 Methodology: EDP Summarisation
- 14. 14 Virtually Materialised A-Box: expanded EDP A1, B1 (1) A2, B2 (1) A-Box: A1(o1) B1(o1) A2(o2) B2(o2) R(o1, o2) T-Box: A1⊆A, A2⊆A, B1⊆B, B2⊆B R (1:1) A, B, A, B,
- 15. Linked Dataset Analysis Results • Dataset Selection & Summary • Analysis Results
- 16. 16 Dataset Selection and Summary LOD 2011
- 17. 17 A-Box Only: Semantic Redundancies – Redundant Triples – Semantic redundancy ratio, i.e. – # Graph Patterns used to substitute redundant triples
- 18. 18 A-Box Only: Syntactic Redundancies – the redundant resource occurrences of inter-structural redundancies – the syntactic redundancy ratio, i.e.
- 19. 19 A-Box & T-Box: No Linkage DBLP2013: SWRC ontology Ordnance Survey: official published OS ontology 1.7% 184% 108% 4.7%
- 20. 20 A-Box & T-Box: No Linkage First 3 datasts are reusing FOAF Ontology – the number of directly used terms from reused T-Box – the number of applicable axioms from (materialised) reused T-Box 26.9% 4% 45.4% 1.3%
- 21. 21 Conclusion • LOD redundancy are heterogeneous & huge • Vocabulary linkage might lead to huge number of derivable triples • Redundancy aware techniques are demanded
- 22. 22 Redundancy-aware Consumption • Compression: different redundancies might need different techniques • For Data Access: (high inter-structure redundancy) skewed entity distributions over EDPs -> efficient access? • OBDA/Reasoning: A-Box redundancy = less T-Box axioms • Data Publisher: should be aware of the consequences of reusing
- 23. Thanks! Q & A