1. Guarding a Walled Garden - Semantic Privacy Preferences for the Social Web Philipp Kärger and Wolf Siberski L3S Research Center, Hannover, Germany
Philipp Kärger - L3S Research Center
05/05/19

2. Outline Observations and Problem Statement A Unified Privacy Model
Implementation using OpenSocial
Future Work and Conclusions
Philipp Kärger - L3S Research Center
05/05/19

3. Observations and Problem Statement
Philipp Kärger - L3S Research Center
05/05/19

4. Privacy Decisions: who and what
Who is requesting?
Do I know the guy?
Did I ever meet him?
Did I ever talk to him?
Is he a colleague?
Didn’t I meet him at ESWC?
What is requested?
Is the requested thing/action private?
Do I want to share the requested thing?
Isn't it the picture I took once at this nice ESWC talk?
Philipp Kärger - L3S Research Center
05/05/19

5. The Who and the What reflected on the Social Web:
Philipp Kärger - L3S Research Center
05/05/19

6. But what about … … the social context? You are allowed if you …
posted in my forum.
are my friend in either Facebook or Skype.
are in one of my Orkut groups.
are in any of my Flickr pictures.
attended ESWC.
like the same music.
are interested in Semantic Web.
are listed in my FOAF profile.
… the social context?
Philipp Kärger - L3S Research Center
05/05/19

7. Privacy Preferences are Trapped
Platforms share similar concepts like
friends
groups
messages and chats
profile information
blocked users
shared resources
But privacy preferences cannot be exported and reused.
Philipp Kärger - L3S Research Center
05/05/19

8. Summary: Motivation Privacy Preferences on the Social Web
are restricted to predefined categories (fixed Whos and Whats)
cannot refer to social context - although it is available (Walled Garden No. 1)
cannot be exported and reused crossing platforms (Walled Garden No. 2)
Philipp Kärger - L3S Research Center
05/05/19

9. A Unified Model for Privacy Preferences
Philipp Kärger - L3S Research Center
05/05/19

10. “Somebody is allowed to do/see something.”
A Privacy Preference is a mapping from
What to Who
Set of actions/objects to Set of persons
Object category to Subject category
Philipp Kärger - L3S Research Center
05/05/19

11. Object and Subject Categories
users shall be allowed to define
new subject categories
e.g., “A family member is every person who is in my FOAF profile or in my Facebook group ‘family’.”
family_member(X) :- foafFriend(X) ; inFacebookGroup(X,’family’).
new object categories
e.g., “A party picture is everything which is a picture and tagged with ‘party’.”
party_picture(X) :- picture(X) , taggedWith(X,’party’).
Philipp Kärger - L3S Research Center
05/05/19

12. And-Or-Tree visualization of categories
Object Categories – the “What” Subject Categories – the “Who”
Philipp Kärger - L3S Research Center
05/05/19

13. User-defined Mappings on Categories
also explain enforcement
enforcement happens acc. to the Mappings
common vocabulary  unified format
Philipp Kärger - L3S Research Center
05/05/19

14. Summary new categories can be defined by rules
party_picture(X) :- picture(X) , taggedWith(X,’party’).
mappings between these categories define privacy preferences
Every party_picture can be accessed by every friend.
platform independent when exploiting a suitable vocabulary
Philipp Kärger - L3S Research Center
05/05/19

15. Implementation
Philipp Kärger - L3S Research Center
05/05/19

16. Goals a uniform representation of Privacy Preferences
 RDF
extend standard Social Web platform to enforce such preferences  the OpenSocial Implementation Apache Shindig
support the integration of arbitrary social contexts for the preferences
 Policy Engine “Protune” plus Social Web wrapper
Philipp Kärger - L3S Research Center
05/05/19

17. Apache Shindig – an Open Social Implementation
Open Social – an API for Social Web sites defining methods for
retrieving personal information (profile data)
getting activity notification
storing/retrieving application data
sending/receiving messages
Apache Shindig
container for hosting Social Web applications
implements Open Social API
basis to easily develop Social Web platforms
Philipp Kärger - L3S Research Center
05/05/19

18. Shindig Extension
filters requests (Open Social API calls) for information about persons
interprets our Privacy Preference Model
Protune is used as policy engine for privacy enforcement
privacy enforcement calls external sources
 used to check social context
family_member(X) :- foafFriend(X) ; inFacebookGroup(X,’family’).
Philipp Kärger - L3S Research Center
05/05/19

19. Philipp Kärger - L3S Research Center
05/05/19

20. Social Context Privacy Preferences can relate to
arbitrary RDF sources, e.g., FOAF, SIOC, DOAP
relationships on Twitter
friendships on Flickr
any OpenSocial information (e.g., age, current location, address)
co-authorship on DBLP (via the DBLP SPARQL endpoint)
Philipp Kärger - L3S Research Center
05/05/19

21. Implementation Summary
each Shindig-based platform can adopt it
reuse and share RDF format of Privacy Preferences
integrate of social context gathered from the Web
Philipp Kärger - L3S Research Center
05/05/19

22. Future Work & Conclusions
Philipp Kärger - L3S Research Center
05/05/19

23. Future Work Authentication and identification User Interface FOAF+SSL
OpenID
certificates, credentials, Trust Negotiation
User Interface
Philipp Kärger - L3S Research Center
05/05/19

24. Philipp Kärger - L3S Research Center
05/05/19

25. Conclusions Social Web Privacy Preferences
share a simple scheme
are limited to concepts of one platform only
are not portable to other platforms
We introduced a new Privacy Preference Model
easily extendable with complex categories
crosses the Walled Garden
Our Implementation
exploits OpenSocial and Protune
uses RDF representation of Privacy Preferences
Philipp Kärger - L3S Research Center
05/05/19

26. Thanks for your attention.
Philipp Kärger
L3S Research Center
Philipp Kärger - L3S Research Center
05/05/19