modelling and reasoning languages for social networks policies

Modelling and Reasoning Languagesfor Social Networks Policies

Guido Governatori and Renato Iannella

EDOC 2009

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The SPIN project: networks, people, information, sharing

Advanced Research on Web 2.0 Platforms for Profiles and Policiestowards improved Interoperability for Online Communities

Partial Profiles

User in ControlExposureMultiple ProfilesDistributed

Semantic Profiles

Increased NetworkThemesOpinionsExperience

Shared Policies

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SPIN Shared Policies

Create an infrastructure to represent policies (e.g., privacy, rights, etc)for social networks. The framework includes languages to define policies,and tools to manipulate and reasoning with the policies

Expressive Language to capturesocial networks concepts

Conceptual languages to allowsfor end user transparency,accountability and policyawareness

Scalable reasoning techniques

Combination of policies: SocialNetwork policies and (multiple)user policies

PrivacyPolicy

Terms&

Conditions

SecurityPolicy

Unified policy

AccessPolicy

MyPublicPolicy

MyPrivatePolicy

MyPublicPolicy

MyPublicPolicy

MyPublicPolicy

MyPrivatePolicy

MyPrivatePolicy

MyPrivatePolicy

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Policy Challenges

Policy Expression – how to unambiguously define the termsand conditions of a policy.

Policy Transparency – how to ensure all parties are aware ofthe policy and its implications.

Policy Conflict – how to detect potential incompatibilitiesbetween dependent policies.

Policy Accountability – how to track policy exceptions andobligations.

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Policies on Social Networks

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Key Policy Language Elements

A clear identification of the Asset (for any type of SocialNetwork content).

Actions that are allowed to be performed (Permissions) or notallowed to be performed (Prohibitions) can be articulated.

All the Parties involved can be specified (who assigns rights towhom).

Any Duties on Parties can be stipulated (their obligations thatmust be meet).

Constraints can be enumerated for any of the key entities.

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ODRL: From Digital Right To Social Network

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Social Network Use Case

Alice wants to give access to her wedding pictures only to peoplethat are fellows on both Flickr and Twitter and that have a blogshe commented at least twice during the last 10 days.

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Dissecting Alice

Identifying the Wedding Photos

Alice is assigning rights

The permission is viewing

The recipient of the permission is the group of people thatmeet all of these criteria

Members of Flickr and Twitter, andHave Blog sites, andAlice has commented at least twice on these blogs,In the last 10 days.

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Alice in ORDL

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FCL: Policy Reasoning

policy conditions have a normative nature;

policy conditions can have exceptions;

conditions in policy can conflict with each other;

policies in a social networks can come from different sources;

policy conditions sometimes involve violations of other policyconditions.

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Alice in Wonderland

Suppose that the network offers members the facility to createblacklists where a member can list members of the networks thatcannot access the member resources, and the user can specifyrestrictions on the resources available to members in a blacklist.

Alice decided that blacklisted members cannot access her resourcesat all. Moreover, suppose that Alice put Bob in the photoblacklist, but she has posted a few recent comments on Bob’sblog, and Bob is a member of the categories listed in Aliceconditions to access her wedding pictures.

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Alice in Wonderland. Chapter 2

The network has another feature. Each user has a profile page, andthe user has to upload a picture to the profile page, and thispicture is available to everybody in the network. Members who donot comply with the above conditions cannot access othermembers’ private resources.

Alice puts a picture of her wedding as her public photo. Carl isanother Flickr and Twitter fellow of Alice (not in her blacklist, andshe repeatedly posted in his blog during the past week) who doesnot have his public picture in his profile.

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FCL Blueprint

Combination of an efficient non-monotonic logic (defeasible logic) and adeontic logic of violation.

Used to model contracts, and business process compliance.

Facts are indisputable statements.

Defeasible rules are rules that can be defeated by contrary evidence.

A1, . . . ,An⇒ C

The superiority relation is a binary relation defined over the set ofrules. The superiority relation determines the relative strength oftwo (conflicting) rules.

Extended with deontic operators O,P,F ,⊗, obligation, permission,prohibition, violation (binary)

A1, . . . ,An⇒ OB1⊗·· ·⊗OBm

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Reasoning with Policies

Positive defeasible conclusions: meaning that the conclusionscan be defeasible proved;

Negative defeasible conclusions: meaning that one can showthat the conclusion is not even defeasibly provable.

1 A is a fact; or2 there is an applicable defeasible rule for A, and either

1 all the rules for ¬A are discarded (i.e., not applicable) or2 every applicable rule for ¬A is weaker than an applicable strict

or defeasible rule for A.

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FCL at Work: Exceptions

Member resources on the network can be access by everybody,unless a resource is declared private

r1 :resource(x)⇒ P access(x)

r2 :private(x),¬owner(x ,y)⇒ Oy¬access(x)

r1 ≺ r2

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FCL at Work: Conflicts

Alice’s wedding pictures policy

p1 : wedding photo(x),flickr(y), twitter(y),

blog(z ,y),posted(a,z , t1),posted(a,z , t2),

t1 > Now −10, t2 > Now −10⇒ Pyaccess(x)

r2 ≺ p1

If a member is a in blacklist then the member cannot accessprivate resources

p2 : private(x),blacklist(y)⇒ Oy¬access(x)

p1 ≺ p2

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FCL at Work: Violations

1 each member has to upload a picture to the profile page, andthis picture is available to everybody in the network

2 members who do not comply with the above conditionscannot access other members’ private resources

r3 : ⇒ Oxpublish public⊗Ox¬access(y)

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Where are we?

fully implemented FCL rule engine (SPINdle, open source)

implementing a policy based social network server (prototype)

basic conflict detection and conflict resolution

What’s missing?

user friendly policy editor

better models of policy integration

scalability study

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modelling and reasoning languages for social networks policies

Social Media

alice conditions

social network policies

members private resources

social networkc nicta

social networksc nicta

policy exceptions

policy accountability

policy transparency