23rd International World Wide Web Conference, 10th April 2014, Seoul, Korea

TripleProvEfficient Processing of Lineage

Queries over a Native RDF Store

Marcin Wylot1, Philippe Cudré-Mauroux1, and Paul Groth2

1) eXascale Infolab, University of Fribourg, Switzerland 2) Web & Madia Group, VU University Amsterdam, Netherlands

Outline

➢ Motivation

➢ Provenance Polynomials

➢ System

➢ Results

Data Provenance

“Provenance is information about

entities, activities, and people involved

in producing a piece of data or thing, which can be used to form

assessments about its quality, reliability or trustworthiness.”

How a query answer was derived: what data was

combined to produce the result.

Data Integration

➢ Integrated and summarized data

➢ Trust, transparency, and cost

➢ Capability to pinpoint the exact source from which the result was selected

➢ Capability to trace back the complete list of sources and how they were combined to deliver a result

Querying Distributed Data SourcesHow exactly was the answer derived?

Application: Post-query Calculations

➢ Scores or probabilities for query result

➢ Result ranking

➢ Compute trust

➢ Information quality based on used sources

Application: Query Execution

➢ Modify query strategies on the fly

➢ Restrict results to certain subset of sources

➢ Restrict results w.r.t. queries over provenance

➢ Access control, only certain sources will appear

➢ Detect if result would be valid when removing certain

source

Provenance Polynomials

➢ Ability to characterize ways each source contributed

➢ Pinpoint the exact source to each result

➢ Trace back the list of sources the way they were combined

to deliver a result

Graph-based Query

select ?lat ?long ?g1 ?g2 ?g3 ?g4where {

graph ?g1 {?a [] "Eiffel Tower" . } graph ?g2 {?a inCountry FR . } graph ?g3 {?a lat ?lat . } graph ?g4 {?a long ?long . }

}

lat long l1 l2 l4 l4, lat long l1 l2 l4 l5,lat long l1 l2 l5 l4, lat long l1 l2 l5 l5,lat long l1 l3 l4 l4, lat long l1 l3 l4 l5,lat long l1 l3 l5 l4,lat long l1 l3 l5 l5,

lat long l2 l2 l4 l4, lat long l2 l2 l4 l5,lat long l2 l2 l5 l4, lat long l2 l2 l5 l5,lat long l2 l3 l4 l4, lat long l2 l3 l4 l5,lat long l2 l3 l5 l4, lat long l2 l3 l5 l5,

lat long l3 l2 l4 l4, lat long l3 l2 l4 l5,lat long l3 l2 l5 l4, lat long l3 l2 l5 l5,lat long l3 l3 l4 l4, lat long l3 l3 l4 l5,lat long l3 l3 l5 l4,lat long l3 l3 l5 l5,

TripleProv Resuls

result: lat, long

provenance polynomial:(l1 ⊕ l2 ⊕ l3) ⊗ (l4 ⊕ l5) ⊗ ( l6 ⊕ l7) ⊗ (l8 ⊕ l9)

Polynomials Operators

➢ Union (⊕)

○ constraint or projection satisfied with multiple sources

l1 ⊕ l2 ⊕ l3

○ multiple entities satisfy a set of constraints or projections

➢ Join (⊗)

○ sources joined to handle a constraint or a projection

○ OS and OO joins between few sets of constraints

(l1 ⊕ l2) ⊗ (l3 ⊕ l4)

Example Polynomial

select ?lat ?long where { ?a [] ``Eiffel Tower''.?a inCountry FR .?a lat ?lat .?a long ?long .

}

(l1 ⊕ l2 ⊕ l3) ⊗ (l4 ⊕ l5) ⊗ ( l6 ⊕ l7) ⊗ (l8 ⊕ l9)

Example Polynomial

select ?l ?long ?lat where {

?p name ``Krebs, Emil'' .

?p deathPlace ?l .

?c [] ?l .

?c featureClass P .

?c inCountry DE .

?c long ?long .

?c lat ?lat .

}

[(l1 ⊕ l2 ⊕ l3) ⊗ (l4 ⊕ l5)] ⊗

[( l6 ⊕ l7) ⊗ (l8) ⊗ (l9 ⊕ l10) ⊗ (l11 ⊕ l12) ⊗ (l13)]

Granularity Levels

➢ source-level: sources of a triples

➢ triple-level: all pieces of data used to answer the query

(l1 ⊕ l2) ⊗ (l3 ⊕ l4)

System Architecture

Native Data Model

➢ Semantically co-located data

➢ Template based molecules

Various Physical Storage Models

Differences:➢ ease of implementation➢ memory consumption➢ query execution➢ interference with the original concept of molecule

1) SPOL 2) LSPO 3) SLPO 4) SPLO

Annotated Triples

➢ Annotated provenance

➢ Quadruples

➢ Easy to implement

➢ Source data repeated

for each triple

Co-located Elements

➢ Data grouped by source

➢ Physically co-located

➢ Avoids duplication of the

same source inside a

molecule

➢ Data about a given subject

co-located in one molecule

➢ More difficult to implement

Experiments

How expensive it is to trace

provenance?

What is the overhead on query

execution time?

Datasets

➢ Two collections of RDF data gathered from the Web

○ Billion Triple Challenge (BTC): Crawled from the linked

open data cloud

○ Web Data Commons (WDC): RDFa, Microdata

extracted from common crawl

➢ Typical collections gathered from multiple sources

➢ sampled subsets of ~110 million triples each; ~25GB each

Workloads

➢ 8 Queries defined for BTC○ T. Neumann and G. Weikum. Scalable join processing on very large rdf

graphs. In Proceedings of the 2009 ACM SIGMOD International Conference on Management of data, pages 627–640. ACM, 2009.

➢ Two additional queries with UNION and OPTIONAL

clauses

➢ 7 various new queries for WDC

http://exascale.info/tripleprov

Results

Overhead of tracking provenance compared to

vanilla version of the system for BTC dataset

source-level co-located

source-level annotated

triple-level co-located

triple-level annotated

Conclusions

➢ provenance overhead is considerable but acceptable,

on average about 60-70%

➢ most suitable storage model depends upon data and

workloads characteristics

➢ annotated: more appropriate for heterogenous datasets

and workloads retrieving provenance

➢ co-located: more appropriate for homogenous datasets

and workload filtering by source

Future Work

➢ Distributed version

➢ Dynamic storage model

➢ Adaptive query execution strategies

➢ PROV output

➢ Over provenance queries

Summary

➢ TripleProv: an efficient triplestore tracking provenance

➢ Two storage models

➢ Fine-grained multilevel provenance tracing

➢ Formal provenance polynomials

➢ Experimental evaluation

http://exascale.info/tripleprov

Loading & Memory

Billion Triple Challenge

Web Data Commons

Results

Overhead of tracking provenance compared to

vanilla version of the system for WDC dataset

source-level SLPO

source-level SPOL

triple-level SLPO

triple-level SPOL

Polynomials: multiple records

[(l1 ⊕ l2 ⊕ l3) ⊗ (l4 ⊕ l5) ⊗ ( l6 ⊕ l7) ⊗ (l8 ⊕ l9)]

⊕

[(l5 ⊕ l7) ⊗ (l4) ⊗ ( l13 ⊕ l17) ⊗ (l28)]

⊕

[(l4) ⊗ (l1 ⊕ l2) ⊗ ( l3 ⊕ l7) ⊗ (l8 ⊕ l9⊕ l4)]