policy representation & reasoning
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Policy Representation & Reasoning
Juri L. De Coi, Philipp Kärger, Daniel Olmedilla, Sergej Zerr
L3s Research Center / Leibniz Hannover University
L3S Research SeminarHannover, 18th April, 2008
De Coi, Kärger, Olmedilla, Zerr 2
Best Student Award at VIT: Sukriti RameshCONGRATULATIONS!!
Because of• Academic performance (last 4
years)• Personality & communication skills• Social work• Project work (including L3S)
Even though it was with Odysseas
But especially because of her answer to what does Mahatma's Gandhi phrase "See no evil, hear no evil, speak no evil" mean for you? Ask her for details !
April 18th, 2008 2L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr 3
Increasing Seminar Attendance Seminar Appeal
Wolfgang and Wolf-Tilo agree with the formula
They wanted to take an action, as the winners in the L3S Workshop did so they decided to
Sponsor ice cream today ! Voluntarily !!!!!
April 18th, 2008 3L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Outline
Introduction to Policy Representation & Reasoning Motivation, requirements, state of the art
L3S Policy framework Protune in a Nutshell: framework and language
Protune in Action: Policies on the Web Static content protection and dynamic
generation
Reactive Policies, Current and Further Policy Work Event reactivity, research ideas
April 18th, 2008 4L3S Research Seminar
Introduction:Policy Representation &
Reasoning
Daniel Olmedilla
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningProblem
Institutions, companies and people need to control the way they Make business Take decisions Offer their assets Etc …
Computers help us on our daily work performing tasks that we cannot perform (or we do it worse)
hard to control manually, time-consuming, expensive, error-prone
automatically on our behalf
But generally, we need to control how decisions and actions are taken
April 18th, 2008 6L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr 7
Policy Representation & ReasoningWhat is a Policy?
Wikipedia: deliberate plan of action to guide decisions and
achieve rational outcome(s) Not necessarily related to IT
In an IT setting: Set of considerations designed to guide decisions of
courses of actions
Broad definition: Set of statements defining the behaviour of an
entity in a given situation
April 18th, 2008 7L3S Research Seminar
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Policy Representation & ReasoningPolicies are everywhere (I)
Rules of ethics for robots
1. A robot may not injure a human being or, through inaction, allow a human being to come to harm.
2. A robot must obey orders given to it by human beings, except where such orders would conflict with the First Law.
3. A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.
[Isaac Asimov. Runaround. 1942 ]
April 18th, 2008 8L3S Research Seminar
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Policy Representation & ReasoningPolicies are everywhere (II)
Declarative
April 18th, 2008 9L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningPolicies are everywhere (III)
April 18th, 2008 10L3S Research Seminar
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Policy Representation & ReasoningPolicies are everywhere (IV)
B2B contracts e.g. quantity flexible contracts, late delivery penalties,
etc. Negotiation
e.g. rules associated with auction mechanisms Security
e.g. access control policies Privacy
Information Collection Policies (aka “ P3P Privacy Policies”)
Obfuscation Policies Workflow management
What to do under different sets of conditions Context aware computing
What service to invoke to access a particular contextual attribute
Context-sensitive preferences[ by Norman Sadeh, Semantic Web Policy Workshop panel, ISWC 2005 ]
April 18th, 2008 11L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningThe goal
Build applications/agents whereBehaviour is flexible
Can be changed/updated dynamically without re-coding, re-compiling, re-
installing, etc… In a costless manner
Can be managed by administrators/users without needing to be computer experts
Can be understood by normal users
April 18th, 2008 12L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningBenefits
Explicit license for autonomous behaviour Reusability Efficiency Extensibility Context-sensitivity Verifiability Support for simple as well as sophisticated agents Protection from poorly-designed, buggy or malicious
agents Reasoning about agent behaviour Compact representation, possibly declarative Etc.
April 18th, 2008 13L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningRequirements / Challenges
Many policies, one frameworkConflict Resolution Integration with external sourcesPolicies as active objects
Executing actionsNegotiationsUser awareness and controlCooperative enforcement
April 18th, 2008 14L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & Reasoning Many policies, one framework (I)
The term policy covers: Security/Privacy policies, Trust management
Business rules
Quality of Service directives
Service-level agreements
Communication and conversation policies and more...
In many cases they are interleaved
If customers are younger than 26 give a 20% discount on international tickets
Up to 15% of network bandwidth can reserved if payment is done with an accepted credit card
Customers can rent a car if they are 18 or older, and exhibit a driving license and a valid credit card
April 18th, 2008 15L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningMany policies, one framework (II)
It is appealing to integrate all policies in one framework
One common infrastructure for interoperability and decision
making
Where policies can be harmonized & coordinated
April 18th, 2008 16L3S Research Seminar
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Policy Representation & ReasoningConflict Resolution (I)
Ivan
Alice
You can access
file123.txt
You can not access
file123.txt
You must inform your
boss
You don’t need to inform your
boss
Positive authorization
Negative authorization
Obligation
Dispensation
April 18th, 2008 17L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningConflict Resolution (II)
Security typically assumes “everything is denied by default” no need for disallow policies
The cost of disclosing a sensitive resource is higher than not disclosing a public one
But, if there exists the need, then it is required to provide techniques for
Conflict detection
Conflict harmonization
April 18th, 2008 18L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr 19
Policy Representation & ReasoningIntegration with external systems
Policies are not islands
Decisions need data, information, and knowledge
Each organization has its own
Already available through legacy software and data
A realistic solution must interoperate with them
Third parties
Credit card sites for validity checking
External databases Variety of web resources
April 18th, 2008 19L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningNegotiations (I)
Step 1: Alice requests a service from Bob
Step 5: Alice discloses her VISA card credential
Step 4: Bob discloses his BBB credential
Step 6: Bob grants access to the serviceService
BobAlice
Step 2: Bob discloses his policy protecting the service
Step 3: Alice discloses her policy protecting the VISA
April 18th, 2008 20L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningNegotiations (II)
Used for Access control Service-level agreements Dynamic contracts
E.g., in web service composition
Autonomic computing
Pervasive environments
E.g., sensor networks
Etc.
April 18th, 2008 21L3S Research Seminar
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Policy Representation & ReasoningUser awareness and control
Explain policies and system decisions Make rules & reasoning intelligible to the common user
Encourage people to personalize their policies Make it easy for users to write their own rules
April 18th, 2008 22L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
Policy Representation & ReasoningCooperative Policy Enforcement
Crucial for the success of a service
Never say (only) “no”!
Encourage first-time users
Who don't know how to use your service
Explain policy decisions
Especially failures
Advanced queries: Why not
Advanced queries: How-to, What-if
You can’t open this door, but
you can ask Alice for permission
April 18th, 2008 23L3S Research Seminar
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Policy Representation & ReasoningMain State of the Art Approaches
Ponder OO language, well established, focus on network
management
XACML Standard by OASIS, it being taken up by companies
KAOS Based on DL reasoning
REI
Combination of DL representation and LP semanticsPeerTrust
Based on guarded distributed logic programs
And many othersApril 18th, 2008 24L3S Research Seminar
Protune policy framework:
Juri Luca De Coi
(not too)technical details
De Coi, Kärger, Olmedilla, Zerr
Protune Policy FrameworkOutline
Getting started
Protune Features
Usability issues
April 18th, 2008L3S Research Seminar 26
Getting started
De Coi, Kärger, Olmedilla, Zerr
Intelligentpolicyengine
Policy……….
Alice Bob
Request
Protune Policy FrameworkOverview
April 18th, 2008L3S Research Seminar 28
Decision
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Just to get the flavor...
disclose(‘/EWSCpaper2008.pdf’) sendL3SEmployeeId.
disclose(X) status(X, published).
status(‘/EWSCpaper2007.pdf’, published).
status(‘/EWSCpaper2008.pdf’, notPublished).
April 18th, 2008L3S Research Seminar 29
EWSCpaper2008.pdf can be disclosed to the other peer if it has sent an L3S
employee id.
A resource can be disclosed if its
status is „published“
IF conditions are fullfilled
THEN allow action
Protune Features
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Standard example
disclose(X) status(X, notPublished),sendL3SEmployeeId.
status(‘/EWSCpaper2007.pdf’, published).
status(‘/EWSCpaper2008.pdf’, notPublished).
April 18th, 2008L3S Research Seminar 31
Actions may be needed in order
to make decisions
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Metapolicy “type”
disclose(X) status(X, notPublished),sendL3SEmployeeId.
status(‘/EWSCpaper2007.pdf’, published).
status(‘/EWSCpaper2008.pdf’, notPublished).
sendL3SEmployeeId->type:action.
status(X, Y)->type:logical.
April 18th, 2008L3S Research Seminar 32
Action
Usual predicate
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Metapolicy “actor”
disclose(X) status(X, notPublished),sendL3SEmployeeId.
status(‘/EWSCpaper2007.pdf’, published).
status(‘/EWSCpaper2008.pdf’, notPublished).
sendL3SEmployeeId->type:action.
sendL3SEmployeeId->actor:peer.
status(X, Y)->type:logical.
April 18th, 2008L3S Research Seminar 33
Who executes
the action?The requester?
The local system?A third party?
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Available actions
Access to relational databases
Access to RDF repositories
Credential exchange
Searching of regular expressions within a file
Interface to an LDAP server
Time and location management
April 18th, 2008L3S Research Seminar 34
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Explanations
April 18th, 2008L3S Research Seminar 35
Usability issues
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Usability issues
download(User, Resource) authenticated(User), have(User, Subscription),availableFor(Subscription, Resource).
authenticated(‘Bob’).have(‘Bob’, lncsSubscription).availableFor(lncsSubscription, ESWCpaper2007.pdf).authenticated(User)->type:logical.availableFor(Subscription, Resource)->type:logical.have(User, Subscription)->type:logical.
April 18th, 2008L3S Research Seminar 37
Every user who is authenticated and who has a subscription that
is available for a resource can download
the resource.
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Using natural language: Problem
How to deal with ambiguities?
April 18th, 2008L3S Research Seminar 38
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Using natural language: Ambiguities (I)
April 18th, 2008L3S Research Seminar 39
Bob looks at the girl on the hill with a telescope
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Using natural language: Ambiguities (II)
April 18th, 2008L3S Research Seminar 40
2 girls lift 2 tables
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Solution: Use a controlled natural language
What does “controlled” mean? Rules are used in order to
automatically disambiguate ambiguous sentences Bob looks at the girl on the hill
with a telescope
Only a subset of valid English sentences are valid sentences
April 18th, 2008L3S Research Seminar 41
Example disambiguation rule:Propositional phrases refer to the predicate of the
sentence
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Disambiguation: using ACE (I)
April 18th, 2008L3S Research Seminar 42
Bob looks at the girl on the hill with a telescope
Bob looks with a
telescope at the girl who
is on the hill.
Bob looks at the girl on
the hill with a telescope.
Bob looks at the girl who
is on the hill with a telescope.
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework Disambiguation: using ACE (II)
April 18th, 2008L3S Research Seminar 43
2 girls lift 2 tables
2 girls lift 2 tables.
Each of 2 girls lifts one table.
Each of 2 girls lifts 2
tables.
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework The ACE Protune translation (I)
April 18th, 2008L3S Research Seminar 44
Every user who is authenticated and who has a subscriptionthat is available for a resource can download the resource.
drs([], [ drs([A, B, C, D, E, F, G, H], [
object(A, user, countable, na, eq, 1)-1, property(B, authenticated, pos)-1,
predicate(C, be, A, B)-1, object(D, subscription, countable, na, eq, 1)-1,
object(E, resource, countable, na, eq, 1)-1, property(F, available, pos)-1,
predicate(G, be, D, F)-1, modifier_pp(G, for, E)-1,
predicate(H, have, A, D)-1 ])
=> drs([], [
<> drs([I], [
predicate(I, download, A, E)-1 ]) ])]).
download(User, Resource) authenticated(User),
‘available#for’(Subscription, Resource), have(User, Subscription).
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework The ACE Protune translation (II)
April 18th, 2008L3S Research Seminar 45
Every user who provides a declaration whoseusername is the user's name and whose password
is the user's password is authenticated.
authenticated(User) User.name:Username,
User.password:Password, provide(User, Declaration),
Declaration.password:Password, Declaration.username:Username.
De Coi, Kärger, Olmedilla, Zerr
Protune Policy Framework The ACE Protune translation (III)
April 18th, 2008L3S Research Seminar 46
Every user who sends a credential• that is valid and• whose type is "creditCard" and• whose owner is authenticated and• on which a price is chargedpays the price with "creditCard".
'pay#with'(User, Price, creditCard) valid(Credential),
Credential.type:creditCard, authenticated(Owner),
'charged#on'(Price, Credential), send(User, Credential),
Credential.owner:Owner.
Policy Based Protection and Personalized Generation
of Web Content
Sergej Zerr
De Coi, Kärger, Olmedilla, Zerr
Protune in Action: Policies on the WebTrust within an Open Environment
April 18th, 2008L3S Research Seminar 48
BookstoreWeb server LMS
Ax
Bx
x
De Coi, Kärger, Olmedilla, Zerr
Protune in Action: Policies on the WebUsing Trust Negotiation
April 18th, 2008L3S Research Seminar 49
Servlet Container(e.g Tomcat)
PolicyFilter.Jar
<poljsp:policycondition policyname="exchangedCredential(member)“ >
<poljsp:iftrue>Success!!</poljsp:iftrue></poljsp:policycondition>
Appletx
var protectedResources=new Array( ‘http://test.de/test.jsp‘ );
Web Package
1. Reactive Policies2. More policy research topics
Philipp Kärger
De Coi, Kärger, Olmedilla, Zerr
Reactive PoliciesWhile doing valuable research …
April 18th, 2008L3S Research Seminar 51
Notify me if one of my contacts has
birthday and goes online.
If someone phones me while I
am on a call, deny the call
and open a chat instead.
Show my date of birth only to family
members.
Automatically accept “share
contact dates” for L3S members and for the contacts of
my family.
Always accept files sent by L3S members but only if it’s not an
exe file.
My students
can call me only on
Wednesday morning. After the semester, deny their
calls.
L3S members can only call me
during business hours.
De Coi, Kärger, Olmedilla, Zerr
Reactive PoliciesCurrent Policies
they define under which conditions things are true, e.g.,
who exactly gets access why we grant access what is needed to get access
April 18th, 2008L3S Research Seminar 52
De Coi, Kärger, Olmedilla, Zerr
Reactive PoliciesWhat is a reactive policy?
But what is missing in current policy
frameworks?
When is the policy evaluated? Triggering Events
What exactly happens if a policy is evaluated to true or false?
Actions (as reactions to events)
April 18th, 2008L3S Research Seminar 53
IF EVENT “call comes in” HAPPENSAND “I am on another call” HOLDS
PERFORM ACTION “deny call and open chat”
If someone phones me while
I am on a call, deny the call
and open a chat instead. Reactivity!
De Coi, Kärger, Olmedilla, Zerr
Reactive PoliciesReactivity
Reactivity in Databases:“Active Database Systems”, Book, 1995many more
Reactivity on the web:“An Event Condition Action Language for XML”,
WWW2002EDBT 2006 Workshop “Reactivity on the Web”REWERSE Work Package “Evolution and Reactivity”some more
April 18th, 2008L3S Research Seminar 54
De Coi, Kärger, Olmedilla, Zerr
Reactive PoliciesApproach
Claim:We need policies that allow for reactivity.
Solution:Reactive Policies
also called Event Condition Action Policies
April 18th, 2008L3S Research Seminar 55
De Coi, Kärger, Olmedilla, Zerr
Reactive PoliciesEvent Condition Action Policies
- always three components:- Event: when is the rule evaluated- Condition: what has to be satisfied- Action: what is the reaction to the event
ON a call comes inIF I am on another callDO deny call and open chat
April 18th, 2008L3S Research Seminar 56
If someone phones me while
I am on a call, deny the call
and open a chat instead.
De Coi, Kärger, Olmedilla, Zerr
Reactive PoliciesSolution
How do we get all this to work?
r³ and ProtuneCombining a Reactive Framework and a Policy
Framework
April 18th, 2008L3S Research Seminar 57
De Coi, Kärger, Olmedilla, Zerr
Reactive Policiesr3 – Resourceful Reactive Rules
(developed at the AI Center, Universida de Nova de Lisboa (Portugal))
(Semantic) Web Rule Engine for Reactive Rulesevaluates rules of the form:
<rule><event>myEventLanguage:SkypeCallComesIn(User)</event><condition>myConditionLanguage:isNotTrusted(User)</condition><action>myActionLanguage:denyCall(User)</action>
</rule>
plugging in arbitrary languages makes it really flexible
April 18th, 2008L3S Research Seminar 58
De Coi, Kärger, Olmedilla, Zerr
Reactive PoliciesCombining r3 and Protune
April 18th, 2008L3S Research Seminar 59
Protune external actions
any event language (e.g., XChange,
Prova)
<rule>
<event>myEventLanguage:SkypeCallComesIn(User)</event>
<condition>PROTUNE:isNotTrusted(User)</condition>
<action>PROTUNE:denyCall(User)</action></rule>
Protune goals
De Coi, Kärger, Olmedilla, Zerr
Reactive PoliciesBenefits
April 18th, 2008L3S Research Seminar 60
Protune• allows for negotiations,
information exchange• provides explanations
• allows for (external) actions
r³• allows for arbitrary event
languages • evalutates Event Condition
Action rules• handles the binding across events, conditions, actions
making policies reactive
enhance reactivity with
policies
De Coi, Kärger, Olmedilla, Zerr
Reactive Policies Summary
• Reactive Policies – policy-enabled Reactivity• policies need some kind of reactivity
no current policy framework allows for reactivity no current reactive rule framework allows for
policies
• ECA policies provide access control provide semantics for events and actions
• combining r³ and Protune merges both worlds advanced access control with policies engine for reactive rules extends
April 18th, 2008L3S Research Seminar 61
More research ideas …
•Daniel, Juri, Philipp, Sergej, and some more
De Coi, Kärger, Olmedilla, Zerr
More research ideasOutline
1. Changing policies while negotiating.
2. Using preferences to guide decisions in negotiations.
3. Access control to RDF repositories.
4. Access control for desktop sharing.
April 18th, 2008L3S Research Seminar 63
De Coi, Kärger, Olmedilla, Zerr
More research ideas 1. Changing policies while negotiating
Problem: What if I change my policies while my agent is negotiating?
April 18th, 2008L3S Research Seminar 64
I want to call you via Skype.
Ok, you have to prove
that you work for L3S.
Policy:Only university
members can call me.
… New Policy:Only L3S
members can call me.
De Coi, Kärger, Olmedilla, Zerr
More research ideas 2. Preferences guiding negotiations
Problem: What if there are two possibilities to succeed in a negotiation?
April 18th, 2008L3S Research Seminar 65
Philipp Kärger, Daniel Olmedilla, Wolf-Tilo
Balke
“Using Preferences for Credential Disclosure in Policy-Driven Trust
Negotiations.”
Just submitted.
I prefer to disclose my Student ID
instead of disclosing my
passport.
De Coi, Kärger, Olmedilla, Zerr
More research ideas 3. Access control to RDF repositories
• RDF data is accessible only under certain conditions.
• Problem: how to enforce this for querying?
April 18th, 2008L3S Research Seminar 66
Return all triplesFROM
the ones I am interested in
WHERE my conditions are true.
Return all triplesFROM
the ones I am interested in
WHERE my conditions are true.
Return all triplesFROM
the ones I am interested in
WHERE my conditions are true
AND the policy’s conditions
are true.
Return all triplesFROM
the ones I am interested in
WHERE my conditions are true
AND the policy’s conditions
are true.
expansionexpansion
Policies: conditions that have to be fulfilled to access information.
Policies: conditions that have to be fulfilled to access information.
RDF store (sensitive data)
Fabian Abel, Juri Luca De Coi, Nicola Henze,
Arne W. Koesling, Daniel Krause, Daniel
Olmedilla
“Enabling Advanced and Context-Dependent Access Control in RDF
Stores.”
ISWC 2007
De Coi, Kärger, Olmedilla, Zerr
More research ideas 4. Access control for desktop sharing (I)
April 18th, 2008L3S Research Seminar 67
Juri L. De Coi, Ekaterini Ioannou, Arne Koesling, and Daniel Olmedilla.
“Access control for sharing semantic data
across desktops.”
Workshop on Privacy Enforcement and
Accountability with Semantics (PEAS),
2007.
Metadata:author: …
title: …date: …inverted index:
“Is there a document containing ‘FBI’ in the
title?”
“I want access to your private document.”
De Coi, Kärger, Olmedilla, Zerr
More research ideas 4. Access control for desktop sharing (II)
April 18th, 2008L3S Research Seminar 68
Pre-evaluate for each file, each metadata, and each user.
PoliciesPolicies
Policies: Who is allowed to see what metadata of what file under which conditions.
De Coi, Kärger, Olmedilla, Zerr
End of the SeminarLet us give you a policy
ON seminar just finishedIF you liked it
ORyou had fun ORyou learned something ORyou liked the ice cream
DO big applause
April 18th, 2008L3S Research Seminar 69
De Coi, Kärger, Olmedilla, Zerr
Questions?
decoi@L3S.de – http://www.L3S.de/web/DECOIkaerger@L3S.de – http://www.L3S.de/web/KAERGER
olmedilla@L3S.de – http://www.olmedilla.info/zerr@L3S.de – http://www.L3S.de/web/ZERR
Thanks!
April 18th, 2008 70L3S Research Seminar
De Coi, Kärger, Olmedilla, Zerr
References
• Antoniou et al., Rule-based policy specification. Secure Data Management in Decentralized Systems. Springer, 2007.http://www.l3s.de/~olmedilla/pub/2007/2007_bookDDMS_rule_policies.pdf
• Bonatti, Olmedilla. Rule-based policy representation and reasoning for the semantic web. In Reasoning Web, Third International Summer School 2007. Springer.http://www.l3s.de/~olmedilla/pub/2007/2007_ReasoningWeb-policies.pdf
• Antoniou et al. (Eds.): Reasoning Web 2007. Springer LNCS 4636, pp.1–153
• Bradshaw et al., Making Agents Acceptable to people, Intelligent technologies for information analysis: Advances in agents, data mining and statistical learning. Springerhttp://www.ihmc.us/research/projects/KAoS/biit-jeff.pdfApril 18th, 2008L3S Research Seminar 71
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