semantic web policies

Semantic Web Policies - A Discussion Semantic Web Policies - A Discussion ofof

Requirements and Research IssuesRequirements and Research Issues

SHIVARAMAN SHIVARAMAN RAGHURAMANRAGHURAMAN

MUKESH MUKESH SUSILKUMARSUSILKUMAR

OUTLINEOUTLINE

• About various policiesAbout various policies

• Roles of policies in enhancing Roles of policies in enhancing security, privacy and usability of security, privacy and usability of Distributed servicesDistributed services

• Discusses about important Discusses about important requirements and open research requirements and open research issues.issues.

OUTLINE(CONT…)OUTLINE(CONT…)

• Discussion is based on the following Discussion is based on the following strategic goals and lines of researchstrategic goals and lines of research-Broad notion of policy.-Broad notion of policy.-Strong and Lightweight evidence.-Strong and Lightweight evidence.-Automated Trust Negotiation.-Automated Trust Negotiation.-Cooperative policy enforcement.-Cooperative policy enforcement.

• How to integrate policies into trust How to integrate policies into trust management framework.management framework.

WHAT ARE POLICIES?WHAT ARE POLICIES?

• Policies are pervasive in web Policies are pervasive in web applications.applications.

• Policies specify the behavior of the Policies specify the behavior of the systemsystem

• They play crucial role in the area of They play crucial role in the area of security, privacy and business rules.security, privacy and business rules.

• They determine the success of the They determine the success of the web servicesweb services

BROAD NOTION OF POLICYBROAD NOTION OF POLICY

• All different policies should be All different policies should be integrated into a single framework.integrated into a single framework.

• These policies include not only access These policies include not only access control but also privacy policies, control but also privacy policies, business rules, quality of service and business rules, quality of service and among others.among others.-Access control policies protects any -Access control policies protects any system open to the internet.system open to the internet.


-Privacy policy protects the user while -Privacy policy protects the user while they are browsing web and accessing they are browsing web and accessing web services.web services.

-Business policy specifies the condition -Business policy specifies the condition that apply to specific customer of that apply to specific customer of web services.web services.

-Other policies specify constraints -Other policies specify constraints related to quality of service.related to quality of service.


• All these policies makes decisions based All these policies makes decisions based on the information of the peer/user on the information of the peer/user involved in the transaction.involved in the transaction.-For example, age, nationality, customer profile, identity, and reputation may all be considered both in access control decisions, and in determining which discounts are applicable.


• These kinds of policies needs to be These kinds of policies needs to be integrated to provide integrated to provide – a common infrastructure that can be used for a common infrastructure that can be used for

decision making and interoperability.decision making and interoperability.– Policies can be harmonized and synchronized.Policies can be harmonized and synchronized.

• There are also policies which requires the There are also policies which requires the events to be logged.events to be logged.

• These policies are called Provisional These policies are called Provisional policies.policies.

• Policy specify actions to be executed along Policy specify actions to be executed along with the decision process. with the decision process.


• Policies in these context acts as both Policies in these context acts as both decision support system and as declarative decision support system and as declarative behavior systems.behavior systems.

• An effective approach to policy specification An effective approach to policy specification could give common user a better control on could give common user a better control on the behavior of their own system.the behavior of their own system.

• Achievement of this goal depends on Achievement of this goal depends on policies ability to interoperate with rest of policies ability to interoperate with rest of the system.the system.

STRONG AND LIGHTWEIGHT STRONG AND LIGHTWEIGHT EVIDENCEEVIDENCE

• Policies make decisions based on properties of the peers interacting with the system.

• These properties may be strongly certified by cryptographic techniques, or may be reliable to some intermediate degree with lightweight evidence gathering and validation.

• A flexible policy framework should try to merge these two forms of evidence to meet the efficiency and usability requirements of web applications.

STRONG AND LIGHTWEIGHT STRONG AND LIGHTWEIGHT EVIDENCEEVIDENCE

•Trust negotiation, reputation models, business rules, and action specification languages have to be integrated into a single framework.

•Automated trust negotiation plays an important role in trust management.

TRUST MANGEMENTTRUST MANGEMENT

• The Semantic Web is a large, uncensored system to which anyone may contribute.

• This raises the question of how much credence to give each source. We cannot expect each user to know the trustworthiness of each source.

• This is where Trust Management plays an important role in establishing the trustworthiness of each source.

APPROACHES TO TRUST APPROACHES TO TRUST MANGEMENTMANGEMENT

• Two major approaches to managing trust Two major approaches to managing trust existsexists-Policy-based-Policy-based-Reputation-based-Reputation-based

• In policy-based trust management approach In policy-based trust management approach strong security mechanisms are used to strong security mechanisms are used to regulate access of user to web services.regulate access of user to web services.

• Strong security mechanisms include Strong security mechanisms include signed certificates and trusted certification authorities (CAs).

APPROACHES TO TRUST APPROACHES TO TRUST MANGEMENT (CONT…)MANGEMENT (CONT…)

• Access decisions are based on these Access decisions are based on these mechanism with well defined semantics.mechanism with well defined semantics.

• Provides strong verification and analysis Provides strong verification and analysis support.support.

• Policy-based approach helps in making a Policy-based approach helps in making a decision about the ‘trustworthiness’ of the decision about the ‘trustworthiness’ of the requester.requester.

• Determines whether the service/resource Determines whether the service/resource is allowed or denied to the requester.is allowed or denied to the requester.

APPROACHES TO TRUST APPROACHES TO TRUST MANGEMENT (CONT…)MANGEMENT (CONT…)• Reputation-based trust relies on a “soft

computational” approach to the problem of trust.• In this approach trust is computed based on the In this approach trust is computed based on the

local experience and feedback given by the other local experience and feedback given by the other entities in the network.entities in the network.

--For Example, online buyers and sellers rate each other after each transaction. The ratings pertaining to a certain seller (or buyer) are aggregated by websites reputation system into a number reflecting seller (or buyer) trustworthiness as judged by the webpage community.

APPROACHES TO TRUST APPROACHES TO TRUST MANGEMENT (CONT…)MANGEMENT (CONT…)• The reputation-based approach has been favored

for environments such as Peer-to-Peer or Semantic Web.

• The existence of certifying authorities can not always be assumed but a large pool of individual user ratings is often available.

• Another common approach is to make requester to commit to contract/copyrights by clicking on the “accept” button

• Lightest approach to trust.– Filling an HTML form.

APPROACHES TO TRUST APPROACHES TO TRUST MANGEMENT (CONT…)MANGEMENT (CONT…)• In order to make decisions in Real life scenarios In order to make decisions in Real life scenarios a

combination of these approaches is needed.For Example, Transaction policies must handle expenses of all magnitudes, from micro payments to credit card payments of a thousand euros or even

more. The cost of the traded goods or services contributes to determine the risk associated to the transaction and hence the trust measure required.

• Strong evidence is generally harder to gather and verify than lightweight evidence.

• Sometimes, a “soft” reputation measure or a declaration in the sense outlined above is all one can obtain in a given scenario.

APPROACHES TO TRUST APPROACHES TO TRUST MANGEMENT (CONT…)MANGEMENT (CONT…)• Success of Trust Management depends on Success of Trust Management depends on

the ability of the system to balance trust the ability of the system to balance trust level and risk level for each task.level and risk level for each task.

• The following are two important research The following are two important research directions related to the area of trustdirections related to the area of trust--How should different forms of trust be integrated?--How many different forms of evidence can be conceived?

AUTOMATED TRUST AUTOMATED TRUST NEGOTIATIONNEGOTIATION• Access control presents difficult problems Access control presents difficult problems

in a distributed environment.in a distributed environment.• This problem becomes severe when This problem becomes severe when

resources and subject requesting it belong resources and subject requesting it belong to different security domains.to different security domains.

• Common access control mechanisms Common access control mechanisms provide authorization decisions based on provide authorization decisions based on the identity of the requester which is the identity of the requester which is ineffective.ineffective.

• Automated trust negotiation solves this Automated trust negotiation solves this ineffectiveness.ineffectiveness.

AUTOMATED TRUST AUTOMATED TRUST NEGOTIATIONNEGOTIATION• Attribute credentials are exchanged to

establish trust among strangers who wish to share a resource.

• Automated Trust Negotiation (ATN) is an approach to regulate the exchange of sensitive attribute credentials by using access control policies.

• In ATN peers are able to automatically negotiate credentials according to their own declarative, rule-based policies.

AUTOMATED TRUST AUTOMATED TRUST NEGOTIATION(CONT..)NEGOTIATION(CONT..)

• Rules specify for each resource or credential request which properties should be satisfied by the subjects and objects involved.

• At each negotiation step, the next credential request is formulated essentially by reasoning with the policy, e.g. by inferring implications or computing abductions.

• Thus ATN plays an important role in establishing interoperability among peers.

• Its depends on and actively contributes in the area of Trust Management.


• How Negotiations takes place How Negotiations takes place between peers?between peers?

• Web Server ask for credentials from Web Server ask for credentials from the client requesting resource.the client requesting resource.

• The client in turn asks for server The client in turn asks for server credentials to determine the validity credentials to determine the validity of the server.of the server.

• Both are in symmetrical situation.Both are in symmetrical situation.


•Each peer decides how to react to peer decides how to react to incoming request based on local incoming request based on local policy.policy.

• Local policy is a set of rules written in Local policy is a set of rules written in logic programming.logic programming.

• Requests are formulated based on the Requests are formulated based on the rules from the policies.rules from the policies.

• Several factors are taken into account Several factors are taken into account while formulating requests.while formulating requests.

COOPERATIVE POLICY COOPERATIVE POLICY ENFORCEMENTENFORCEMENT

• It involves both machine-machine It involves both machine-machine and human-machine interaction.and human-machine interaction.

• Machine-machine interaction is Machine-machine interaction is handled by the various negotiation handled by the various negotiation mechanisms as discussed earlier.mechanisms as discussed earlier.

• Human-machine interaction is more Human-machine interaction is more problematic than expected.problematic than expected.

COOPERATIVE POLICY COOPERATIVE POLICY ENFORCEMENT (CONT...)ENFORCEMENT (CONT...)

• Most users lack the technical expertise to Most users lack the technical expertise to tailor existing policies to match their own tailor existing policies to match their own needs, causing easy access to their needs, causing easy access to their protected resources.protected resources.

• Such lack of knowledge on the part of the Such lack of knowledge on the part of the users also affects privacy protection. Most users also affects privacy protection. Most users are not able to personalize their users are not able to personalize their information release policies to suit their information release policies to suit their needs.needs.


• To make the user understand the To make the user understand the meaning of responses better, we bring in meaning of responses better, we bring in co-operative policy enforcement.co-operative policy enforcement.

• This gives users the reasons for negative This gives users the reasons for negative responses and suggestions for how to responses and suggestions for how to avoid such responses in the future.avoid such responses in the future.

•Greater user awareness and control on policies are the main objectives of CPE.


• Policies are made user-friendly by Policies are made user-friendly by usingusing

--rule-based policy specification language-controlled natural language-advanced explanation mechanisms

COOPERATIVE POLICY COOPERATIVE POLICY ENFORCEMENT (CONT…)ENFORCEMENT (CONT…)

•Several novel aspects are described in CPE:-tabled explanation structure

--suitable heuristics for focusing explanations-Heuristics are generic, i.e. domain independent

COOPERATIVE POLICY COOPERATIVE POLICY ENFORCEMENT (CONT…)ENFORCEMENT (CONT…)- combination of tabling techniques

and heuristics yields a novel method for explaining failure.

COOPERATIVE POLICY COOPERATIVE POLICY ENFORCEMENT (CONT…)ENFORCEMENT (CONT…)

• Query answering is conceived for the following

categories of users:– Users who try to understand how to obtain access permissions;– Users who monitor and verify their own privacy policy;– Policy managers who verify and monitor their policies.


• Find the right tradeoff between explanation quality and the effort for instantiating the framework in new application domains. Second generation explanation systems prescribe a sequence of expensive steps, including the creation of an independent domain knowledge base expressly for communicating with the user. This would be a serious obstacle to the applicability of the framework.

NATURAL LANGUAGE NATURAL LANGUAGE POLICIESPOLICIES•Policies should be written by and

understandable to users, to let them control behavior of their system.

•Policies should be formulated based on rules and stated in simple language.

• the inherent ambiguity of natural language is incompatible with the precision needed by security and privacy specifications

CONCLUSIONCONCLUSION

•Policies represents single body of declarative rules used in many possible ways, for negotiations, query answering, and other forms of system behavior control.

•Transparent interoperation based on ontology sharing will determine the success of trust negotiation.

CONCLUSION(CONT…)CONCLUSION(CONT…)

• Users have better understanding and Users have better understanding and control over the policies that govern control over the policies that govern their systems with the help of their systems with the help of Cooperative policy enforcement and Cooperative policy enforcement and Trust Management.Trust Management.

• Policies will have to handle decisions Policies will have to handle decisions under a wide range of risk levels and under a wide range of risk levels and performance requirements.performance requirements.

REFERENCESREFERENCES

1. . Semantic Web Policies - A Discussion of Requirements and Research Issues by P.A. Bonatti1, C. Duma2,N.Fuchs3,W.Nejdl4, D. Olmedilla4, J. Peer5 and N. Shahmehri2

2. M. Y. Becker and P. Sewell. Cassandra: distributed access control policies withtunable expressiveness. In 5th IEEE International Workshop on Policies for

DistributedSystems and Networks, Yorktown Heights, June 2004.3. M. Blaze, J. Feigenbaum, and M. Strauss. Compliance Checking in the Policy-Maker Trust Management System. In Financial Cryptography, British West Indies,February 1998.4. P. A. Bonatti, N. Shahmehri, C. Duma, D. Olmedilla, W. Nejdl, M. Baldoni,C. Baroglio, A. Martelli, V. Patti, P. Coraggio, G. Antoniou, J. Peer, and N. E.Fuchs. Rule-based policy specification: State of the art and future work. Technicalreport, Working Group I2, EU NoE REWERSE, aug 2004. http://rewerse.net/deliverables/i2-d1.pdf.5. P.A. Bonatti, D. Olmedilla, and J. Peer. Advanced policy queries. TechnicalReport I2-D4, Working Group I2, EU NoE REWERSE, Aug 2005.http://www.rewerse.net.

REFERENCESREFERENCES

6. P.A. Bonatti and P. Samarati. A uniform framework for regulating service accessand information release on the web. Journal of Computer Security, 10(3):241–272,2002. Short version in the Proc. of the Conference on Computer and CommunicationsSecurity (CCS’00), Athens, 2000.7. Piero A. Bonatti, Claudiu Duma, Daniel Olmedilla, and Nahid Shahmehri. Anintegration of reputation-based and policy-based trust management. In SemanticWeb Policy Workshop in conjunction with 4th International Semantic Web Conference,Galway, Ireland, nov 2005.8. Piero A. Bonatti and Daniel Olmedilla. Driving and monitoring provisional trustnegotiation with metapolicies. In 6th IEEE International Workshop on Policiesfor Distributed Systems and Networks (POLICY 2005), pages 14–23, Stockholm,Sweden, jun 2005. IEEE Computer Society.9. Paulo P. da Silva, Deborah L. McGuinness, and Richard Fikes. A proof markuplanguage for semantic web services. Technical Report KSL Tech Report KSL-04-01,January, 2004.10. Rita Gavriloaie, Wolfgang Nejdl, Daniel Olmedilla, Kent E. Seamons, and MarianneWinslett. No registration needed: How to use declarative policies and negotiationto access sensitive resources on the semantic web. In 1st European Semantic

semantic web policies - a discussion of requirements and research issues shivaraman raghuraman...

Documents

privacy policies

system policies

different policies

kinds of policies

provisional policies

access control policies

privacy policy