1. Error-Tolerant RDF Subgraph
Matching for Adaptive Presentation
of Linked Data on Mobile
Luca Costabello

2. 2
Mobile Guide
Museum Triplestore
“Is it optimized for my tablet?”
“Does it highlight practical
information when I am on my way?”
“Does it have a visually-impaired mode?”
Example: An RDF-based Mobile Guide for Museums

3. 3
How to enable context-aware adaptation
for Linked Data consumption?
Research Challenges
1. Model context-aware presentation metadata?
2. Select proper presentation metadata at runtime?
“Context” as in [Dey 2001]

4. 4
Modeling Presentation Metadata
1
Selecting Presentation Metadata
with Error-Tolerant Matching
2
Evaluation
3
Conclusions
4

5. 5
Modeling Presentation Metadata
1
Selecting Presentation Metadata
with Error-Tolerant Matching
2
Evaluation
3
Conclusions
4

6. 6
NAC
Laakko
Chen
Zhang
Chamaleon
Butter
Paternò
MIMOSA
CAMB
Adipat
COIN
CSSMedia
Queries
PRISSMA
(OurSystem)
Linked Data
support
✓
Context-awareness
✓ ✓
✓ ✓ ✓ ✓ ✓
✓
Standard Languages
✓ ✓ ✓ ✓ ✓
✓
✓
Runtime adaptation
✓ ✓
✓
✓
Multimodality
✓
Client-side only
(for privacy preservation)
✓ ✓
✓
✓
✓
Evaluation
✓ ✓ ✓ ✓
✓
Adaptive Presentation Frameworks for the Web

7. 7
Presentation Frameworks for the Semantic Web
Haystack
Noadster
Surrogates
Declarative
approach
✓
✓
Domain
Independence
✓
✓
✓
Standard Languages
✓
✓
Context Awareness
Automatic
stylesheets
Evaluation
Distribution
Multimodality
✓
Xenon
Tal4Rdf
LESS
Hidethe
Stack
LDVM
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Fresnel
✓
✓
✓
✓
PRISSMA
(OurSystem)
✓
✓
✓
✓
✓
✓

8. Fresnel [Pietriga et al. 2006]
8
Illustration from [Pietriga et al. 2006]
Content formatting
and additional
content"
Content selection
and ordering"
Styling instructions
for fonts, colors, and
borders"
Presentation Metadata Vocabulary and Rendering Engine for RDF

9. 9
Our Contribution: Extending Fresnel with PRISSMA*
Context
PRISSMA Prism
Context
Description
PRISSMA Context
*Presentation of Resources for Interoperable Semantic and Shareable Mobile Adaptability

10. Extending Fresnel with PRISSMA
10
Context
fresnel:Lens
fresnel:Format
fresnel:group
fresnel:group
Environment
environment
Device
device
User
user
ns.inria.fr/prissma
fresnel:Group
fresnel:purpose
Fresnel
PRISSMA (Our Contribution)
Contextfresnel:Purpose
Prismfresnel:Group
owl:equivalentClass
fresnel:purpose
owl:equivalentClass

11. 11
Example
A Prism for showing and styling titles and
authors of paintings metadata accessed from
inside the museum.

12. 12
:paintingPrism a prissma:Prism, fresnel:Group ;!
fresnel:stylesheetLink <style.css> ;!
fresnel:purpose :atTheMuseum .!
!
:paintinglens a fresnel:Lens;!
fresnel:group :PaintingPrism ;!
fresnel:classLensDomain art:Painting ;!
fresnel:showProperties (dc:title!
dcn:author) .!
!
:depictionFormat a fresnel:Format ;!
fresnel:group :paintingPrism ;!
fresnel:propertyFormatDomain dc:title ;!
fresnel:valueStyle ”title"^^fresnel:styleClass .!
!
:atTheMuseum a prissma:Context ;!
prissma:environment :museumEnv .!
!
:museumEnv a prissma:Environment ;!
prissma:poi :museumGeo .!
!
:museumGeo geo:lat "48.86034" ;!
geo:long "2.337599" ;!
prissma:radius ”200" .!
Lens
Format
Context
prissma:environment
2.337599
48.86034
200
:museumGeo
geo:lat
geo:long
prissma:radius
prissma:poi
prissma:Environment
prissma:Context
:atTheMuseum
:museumEnv
A Prism for showing and styling titles and authors of
paintings metadata accessed from inside the museum.
Example:

13. Examples
PRISSMA Browser for Android
13
Smartphone, user walking
in museum town.
Tablet, user at home.
github.com/lukostaz/prissma-browser/

14. 14
Modeling Presentation Metadata
1
Selecting Presentation Metadata
with Error-Tolerant Matching
2
Evaluation
3
Conclusions
4

15. Selecting Presentation Metadata
15
:smartphoneMoving
:tabletAtHome
:maleVisitorAtTheMuseum
:actualContext

16. 16
Ambiguity
Incompleteness
Selecting Presentation Metadata is tricky
Sensor Noise
2.32434
48.843453
:poi
geo:lat
geo:long
10
prissma:radius
2.337599
48.86034 5
:poi
geo:lat
geo:long
prissma:radius
:user1
"computers"
foaf:interest
:user1
"computer science"
foaf:interest
:user1
:Karl :Anita
prissma:nearbyEntity
:John
:user1
:Karl :Anita
prissma:nearbyEntity
Prism
Actual
Need Error-tolerant matching

17. 17
Error-tolerant matching for RDF Graphs
iSPARQL
Silk
Zou
RDF-specific
✓
✓
✓
Data Heterogeneity
Client-side Execution
(for privacy preservation)
Incremental index updates
✓
Selective matching cache
PRISSMA
✓
✓
✓
✓
Messmer
✓

18. Our Contribution: Adapting Messmer
to RDF and Mobile Context
Optimal error-tolerant subgraph isomorphisms based on graph edit distance.
18
• Atomic element might be
a graph: Context Units
• Core Context Classes
• Entities
• Literals
• Geo
• Time
• Customized Cost Functions
• Strings (Monge-Elkan)
• Geographic (Haversine distance + Decay)
• Temporal (Interval Inclusion + Decay)
• Missing nodes
2.32434
48.843453
:poi
geo:lat
geo:long
10
prissma:radius
Our Extensions:
[Messmer et al. 98]

19. Prism Selection - Step 1: Decomposition
(i.e. Index Building)
19
prissma:environment
2.337599
48.86034
200
:museumGeo
geo:lat
geo:long
prissma:radius
prissma:poi
prissma:Environment
prissma:Context
:atTheMuseum
:museumEnv
prissma:Context
0 48.86034
-2.337599
200
geo:lat
geo:lon
prissma:radius
1
:museumGeo
prissma:Environment
2
{3,1,2,{prissma:poi}}
{4,0,3,{prissma:environment}}
:atTheMuseum
Context Units

20. Prism Selection – Step 2: Online Search Algorithm!
1 foreach context unit S in D do!
2 compute_subgraph_isomorphisms(S,GI)!
3 !
4 while C(fcheapest)< T { !
5 if S1 is Prism then!
6 R.add(S1)!
7 !
8 foreach child of S1 do!
9 fchild= combine(fS1,fS2)!
10 }!
11 return R!
20
prissma:Context
0 48.86034
-2.337599
200
geo:lat
geo:lon
prissma:radius
1
:museumGeo
prissma:Environment
2
{3,1,2,{prissma:poi}}
{4,0,3,{prissma:environment}}
:atTheMuseum
prissma:environment
2.32434
48.843453
:actualPOI
geo:lat
geo:long
prissma:poi
:ActualCtx
:actualEnv
10
prissma:radius
C=0! C=0.34! C=0!
1. Compute context units
isomorphisms costs

21. prissma:Context
0 48.86034
-2.337599
200
geo:lat
geo:lon
prissma:radius
1
:museumGeo
prissma:Environment
2
{3,1,2,{prissma:poi}}
{4,0,3,{prissma:environment}}
:atTheMuseum
Prism Selection: Search Algorithm!
1 foreach context unit S in D do!
2 compute_subgraph_isomorphisms(S,GI)!
3 !
4 while C(fcheapest)< T { !
5 if S1 is Prism then!
6 R.add(S1)!
7 !
8 foreach child of S1 do!
9 fchild= combine(fS1,fS2)!
10 }!
11 return R!
21
prissma:environment
2.32434
48.843453
:actualPOI
geo:lat
geo:long
prissma:poi
:ActualCtx
:actualEnv
10
prissma:radius
C=0! C=0.34! C=0!
C=0.17!
C=0.09!
T=0.6!
✓
✓
✓
✓
✓
2. Combine costs
C < T --> Match!

22. 22
Modeling Presentation Metadata
1
Selecting Presentation Metadata with
Error-Tolerant Matching
2
Evaluation
3
Conclusions
4

23. Evaluation: Memory Consumption
23
0
50
100
150
200
250
300
0.1
0.3
0.5
0.7
0.9
DecompositionItems
Percentage of common context units
Total decomposition Items
Context Units (decomposition)
Context Units (raw prisms)
0
5
10
15
20
25
0.1
0.3
0.5
0.7
0.9
Memory[KB]
Percentage of common context units
PRISSMA decomposition
Jena Models

24. Evaluation: Response Time
24
If prisms are completely different
if prisms are highly
similar
→

25. 25
Modeling Presentation Metadata
1
Selecting Presentation Metadata with
Error-Tolerant Matching
2
Evaluation
3
Conclusions
4

26. 26
Limitations and Future Work
Prisms Distribution:
Linked Presentation Metadata.
Modeling Presentation Metadata
1
Selecting Presentation Metadata
with Error-Tolerant Matching
2
Evaluation
3
User acceptability evaluation
campaign.
Machine learning to optimize cost
functions parameterization.
Beyond Fresnel: support for other
presentation engines
Thanks.
wimmics.inria.fr/projects/prissma
@lukostaz