We present PRISSMA, a context-aware presentation layer for Linked Data. PRISSMA extends the Fresnel vocabulary with the notion of mobile context. Besides, it includes an algorithm that determines whether the sensed context is compatible with some context declarations. The algorithm finds optimal error-tolerant subgraph isomorphisms between RDF graphs using the notion of graph edit distance and is sublinear in the number of context declarations in the system.

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