The document discusses challenges for preserving privacy in linked data from the perspective of a linked data privacy auditing framework. It describes work on ontologies (L2TAP+SCIP) for publishing privacy log events as linked data to enable log integration and encoding of privacy-related events. The framework allows expressing privacy policies and preferences, and performing query-based auditing of linked data uses and flows to check for privacy violations. Examples show how the framework could be applied to an medical research study dataset to log access requests and ensure privacy policy compliance.

1. Privacy‐Aware Preservation:
Challenges from the Perspective of a
Linked Data Privacy Auditing Framework
Mariano P. Consens
University of Toronto
PRELIDA Consolidation and Dissemination Workshop, Riva del Garda, 2014
17/10/2014 Consens

2. A Linked Data Privacy Auditing Perspective?
• Recent work on a Linked Data Publishing Framework
using two RDFS ontologies (L2TAP+SCIP) [SC12,SC14]
– Publishing privacy log events as Linked Data
• Enable log integration via secure web access to all events
– Encoding privacy‐related events in RDF
• Simple target for mapping key Contextual Integrity concepts
– SPARQL solutions for
• Log construction (from policies and dataset descriptions)
• Obligation derivation
• Log‐based auditing of compliance checking (detection of privacy
violations and attribution)
• Facilitates best practices using audit logs and
monitoring as an effective oversight regime
17/10/2014 Consens
[SC14] R. Samavi, M. P. Consens, “Publishing L2TAP Logs to Facilitate Transparency and Accountability”. In
Linked Data on the Web (LDOW2014), WWW Workshops, 2014.
[SC12] R. Samavi, M. P. Consens, “L2TAP+SCIP: An audit‐based privacy framework leveraging Linked Data”. In
8th International Conference on Collaborative Computing (CollaborateCom2012), 2012.

3. Simple Contextual Integrity Ontology
• The SCIP ontology is designed to capture
Contextual Integrity requirements
– Contexts (Participants and their Roles, Data
Attributes, Purposes)
– Norms and Information Transmission Principles
• Privacy as the right to appropriate flows of
personal information
– Social Contexts (roles of individuals in society)
– Context‐relative information norms
Helen Nissenbaum. Privacy in Context: Technology, Policy, and the
Integrity of Social Life, Stanford Law Books, 2009
17/10/2014 Consens

4. Privacy Policies are not just RBAC
Sample Privacy Preferences that could apply to glucose level website
P1: Access by university researchers should be for research purposes
P2: Consent must be obtained at least two days prior to access
P3: Should receive notification of publications using the data within 9 months
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5. L2TAP+SCIP Motivation
• Increasing need for privacy frameworks that allow
– Individuals to express their privacy preferences
– Service providers to interpret, enforce, and be held
accountable for respecting individual’s privacy concerns
• Compliance (e.g., HIPAA Privacy Rule, Gramm‐Leach‐Bliley Act,
EU Directive 95/46/EC)
• EU Agency Recommendation (ENISA, 2011)
– Research on information accountability technology
should be promoted, aimed at the technical ability to
hold information processors accountable for their
storage, use and dissemination of third‐party data.
17/10/2014 Consens

6. Related Work
• Linked Data privacy
– Expressing access control policies, SPPO (ACL) [Sacco, 2011]
– Using SWRL to express access rules [Mühleisen, 2010]
– Leveraging the linked data architecture for providing authorization and
access restrictions (based on WebID) [Story, 2009 ], [Hollenbach et al., 2009 ]
• Policy monitoring approaches
– LPU [Barth et al., 2006], MFOTL [Basin et al., 2010], PrivacyLFP [Datta et al., 2011]
– Use linear, metric temporal logic (LTL, MFOTL)
– Provide proof‐based systems for run time monitoring of policies
• Access control and privacy policy languages
– Expressing access control policies [Sandhu et al., 1996], [Jojodia et al., 2001]
– Expressing and enforcing privacy policies (P‐RBAC) [Ni et al., 2007], [Ni et
al., 2008], [Li et al., 2012]
17/10/2014 Consens

7. Talk Outline
• Background on Perspective, Privacy Policies
• Privacy awareness in OAIS?
• L2TAP Linked Data Logs
– L2TAP Log Events
– SCIP Privacy‐related Events
• Query‐based Auditing
• Closing Remarks
17/10/2014 Consens

8. Privacy‐Aware Preservation in OAIS
• The PDI (Preservation Description Information)
includes Access Rights Information
– Access restrictions pertaining to the Content
Information; including the legal framework, licensing
terms, and access control
– Contains access and distribution conditions stated in
the Submission Agreement, related to both
preservation (by the OAIS) and final usage (by the
Consumer)
– Includes the specifications for the application of rights
enforcement measures
17/10/2014 Consens

9. Privacy‐awareness evolution?
• Changes in OAIS from 2002 (CCSDS 650.0‐B‐1)
to 2012 (CCSDS 650.0‐M‐2)
– Addition of Access Rights Information to PDI
– Removal of Annex A (existing archive examples)
• Of the 5 examples removed, 2 deal with
privacy issues
17/10/2014 Consens

10. Life Sciences Data Archive
• LSDA is responsible for collecting, cataloging,
storing and making accessible the data of NASA
funded Life Sciences space flight investigations
• The LSDA has strict security measures for data
from human subjects which require sensitivity
and secure handling due to the Human Data
Privacy Act
• Only mean‐pooled human data is made available
to the public
– Privacy via Anonymity vs. Usability
17/10/2014 Consens

11. National Collaborative Perinatal Project
• NCPP was a multi‐institutional, multi‐year (1959‐
1965 to 1974) study of pregnant women and the
children born from those pregnancies to provide
baseline information useful for later determining
the causes of neurological diseases
– The NIH NINDS project expended more than $200
million over two decades to collect NCPP
– “It is unlikely that a study of this duration and
magnitude will be repeated”
• NCPP transferred to the National Archives and
Records Administration (NARA)
– After NARA and NIH resolved the privacy and access
concerns
17/10/2014 Consens

12. Privacy as a Value‐added Transformation of NCPP
• NARA provides NCPP as received from NINDS
• NARA has created Public Use Files for the two
data files containing personal identifiers in
conformance with the Freedom of Information
Act and NARA
• NARA enforces restrictions on access to
records whose release might result in
unwarranted invasion of personal privacy
17/10/2014 Consens

13. Talk Outline
• Background on Perspective, Privacy Policies
• Privacy awareness in OAIS?
• L2TAP Linked Data Logs
– L2TAP Log Events
– SCIP Privacy‐related Events
• Query‐based Auditing
• Closing Remarks
17/10/2014 Consens

14. Big (Health) Data Motivation
• Privacy protection a challenge for social
computing and data driven science
• Consider big data biomedical research
– Massive datasets of human genome, biological
imaging, and clinical information collected and
aggregated from individual health records
• Data subjects' privacy in clinical research
– Addressed by multiple legislations and regulations
(e.g., U.S. Department of Health and Human
Services or HHS)
17/10/2014 Consens

15. Scenario: Medical Research Study
• Research teams are interested in analyzing primary reasons
for ICU hospitalization, examine effectiveness of medication
across patient demographics
• MIMIC II is a public clinical database provided by PhysioNet
of data on de‐identified patient ICU admissions
• Researchers must comply with MIMIC II data use
agreement, as well as HHS, Hospital/University, and other
regulations
17/10/2014 Consens
Dataset
MIMIC II
Auditor RT1
Data Provider
Auditor
External
AuditorL2TAP Audit Log
RT2
Data Provider
PhysioNet
L2TAP Audit Log
RT1
Research Team
RT1
Research Team
RT2
Auditor RT2

16. Overview of L2TAP Logs
• L2TAP provides a set of classes and properties
that can be used to represent and publish a
log of privacy events as Linked Data
• L2TAP‐related events in the log
– Log Initialization
• Who is the logger, what time model is used
– Participant Registration
• DataSubject, DataRequestor, DataSender,
ObligationPerformer, ObligationWitness, PrivacyLogger,
PrivacyExpert
17/10/2014 Consens

17. Log Initialization Event
17/10/2014
Who?
Consens

18. Participant Registration Event
17/10/2014
When?
What?
URI minted by
PrivacyLogger
Consens

19. L2TAP Participants in OAIS Scenario
17/10/2014 Consens
Individuals
(as Source of Data)
Auditors
(of Information Flows)

20. Overview of SCIP Privacy‐related Events
• Recap: the SCIP ontology is designed to
capture Contextual Integrity requirements
– Contexts (Participants and their Roles, Data
Attributes, Purposes)
– Norms and Information Transmission Principles
• SCIP encoded privacy‐related events in RDF
– Privacy Preferences
– Access Requests and Responses
– Obligation Acceptances and Performances
– Access Activities
17/10/2014 Consens

21. 17/10/2014 Consens
Research Team
RT1
Data Provider
PhysioNet
Privacy Policies
L2TAP Audit Log
SCIP in the Medical Research Study

22. Privacy Preference
17/10/2014 Consens
Purpose!

23. Privacy Preferences in OAIS Administration
17/10/2014 Consens

24. 17/10/2014 Consens
Access Request
Research Team
RT1
Data Provider
PhysioNet
Privacy Policies
L2TAP Audit Log
SCIP in the Medical Research Study

25. Access Request
17/10/2014 Consens

26. 17/10/2014 Consens
Access Request
Research Team
RT1
Data Provider
PhysioNet
Privacy Policies
L2TAP Audit Log
Access Response
SCIP in the Medical Research Study

27. Access Response
17/10/2014 Consens

28. Requests and Responses in OAIS Access
17/10/2014 Consens

29. 17/10/2014 Consens
Access Request
Research Team
RT1
Obligation Acceptance
Data Provider
PhysioNet
Privacy Policies
L2TAP Audit Log
Access Response
SCIP in the Medical Research Study

30. Obligation Acceptance
17/10/2014 Consens

31. 17/10/2014 Consens
Access Request
Research Team
RT1
Obligation Acceptance
Data Provider
PhysioNet
Privacy Policies
L2TAP Audit Log
Access Response
Performed Obligation
SCIP in the Medical Research Study

32. Performed Obligation
17/10/2014 Consens

33. 17/10/2014 Consens
Access Request
Research Team
RT1
Obligation Acceptance
Access Activity
Data Provider
PhysioNet
Privacy Policies
L2TAP Audit Log
Access Response
Performed Obligation
SCIP in the Medical Research Study

34. Access Activity
17/10/2014 Consens

35. Activities in OAIS Data Management
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36. 17/10/2014 Consens
Access Request
Research Team
RT1
Obligation Acceptance
Access Activity
Data Provider
PhysioNet
Privacy Policies
L2TAP Audit Log
Access Response
Performed Obligation
SCIP in the Medical Research Study

37. L2TAP+SCIP flows affect most OAIS areas!
17/10/2014 Consens

38. Talk Outline
• Background on Perspective, Privacy Policies
• Privacy awareness in OAIS?
• L2TAP Linked Data Logs
– L2TAP Log Events
– SCIP Privacy‐related Events
• Query‐based Auditing
• Closing Remarks
17/10/2014 Consens

39. Log Construction
• Log Construction requires descriptions of the
participants, policies, and access requests
– Data provider motivated to express the policies
that govern data usage
– Research team institution motivated to facilitate
researcher accountability
– Access requests can be derived from dataset
description (SPARQL Construct queries)
• Accommodates multiple log scenarios
– Distribution, Replication, Third‐party custodians
17/10/2014 Consens

40. Obligation Derivation
• Given an access request, we need a mechanism
to log all applicable obligations
• The process consists of the following three tasks:
– find matches between an access request and privacy
preferences
– generate the set of obligations
– construct the logical expression that describes how
the individual satisfaction of each obligation
contributes to the overall compliance of the originally
matched access request
• SPARQL Construct queries to derive the
scip:Obligations that are returned in
scip:AccessResponse
17/10/2014 Consens

41. Compliance Checking via SPARQL
• Algorithm
1. Determine the individual satisfaction of each obligation
(ASK query)
2. Evaluate how the individual satisfaction of each
obligation contributes to the overall compliance of an
access request (multiple ASK queries)
3. Determine the access request compliance (SELECT
query)
• Representative compliance queries
– Which access requests are not compliant at time t?
– Which access requests have been discharged?
– What obligations are pending?
17/10/2014 Consens

42. SELECT DISTINCT ?request
WHERE {
?response scip:responseTo ?request .
?response scip:contextObligation ?obligation .
?response scip:accessDecision ?accessDecision .
FILTER ((!(φt
f) && (φt
p)) && ?accessDecision) }
Step 3 Compliance Checking Query
• Which access requests are not compliant at time t?
• Which access requests have been discharged?
• Which access requests are compliant at time t but are not yet
discharged?
Framework Extensibility:
Φ can be substituted by an
expressions that its
propositional value is deducted
from a more sophisticated
obligation model
4217/10/2014 Consens

43. Experimental Validation
• Experimental validation of the scalability and practicality
– Custom Java application (SyntheticSCIP) used to generate a hypothetical audit
log scenario with a growing number of access requests
– Six representative compliance queries timed using a Virtouso 6 installation on
an Ubuntu server
Q1
Q2
Q3
Q4
10 50 100 400 1,000
Q5
Q6
0
500
1000
1500
2000
2500
Time(seconds)
Access Requests (in thousands)17/10/2014 Consens

44. Talk Outline
• Background on Perspective, Privacy Policies
• Privacy awareness in OAIS?
• L2TAP Linked Data Logs
– L2TAP Log Events
– SCIP Privacy‐related Events
• Query‐based Auditing
• Closing Remarks
17/10/2014 Consens

45. Closing Remarks
• PRELIDA’s list of desirable features for a
Preservable (Link Data) Dataset archive should
consider including Privacy Policies
– Why not using a Linked Data representation?
• Privacy‐aware Preservation has implications
throughout the entire OAIS Reference Model
• Privacy preferences are dynamic
– Age/time‐based policy changes
– The social context of norms change
17/10/2014 Consens

46. Monitoring Policy Changes in OAIS Preservation Planning
17/10/2014 Consens