Semantic Web Services (Standards, Monitoring, Testing and Security)

Semantic Web Services (Standards, Monitoring, Testing and

Security)Department of Engineering-Information

TechnologyPresented by : Reza Ghanbari

2010

Outline• Introduction of Web Service• Semantic Web Services

– Introduction– Life Cycle

• Foundation Standards of Web Service– HTTP– WSDL– SOAP– UDDI

• Foundation Standards of Semantic Web Service• OWL-S• OWL-S Virtual Machine• Monitoring of Semantic Web Service• Security of Semantic Web Service

– Message Level Protection– Message Privacy– Parameter Checking– Authentication– Authorization

• Conclusion of Semantic Web Services• References

Web Service

• A program programmatically accessible over standard

internet protocols

• Loosely coupled, reusable components

• Encapsulate discrete functionality

• Distributed

• Add new level of functionality on top of the current web

Web Services Framework

Problems of Web Services

• Descriptions are syntactic

• It says nothing (in machine - interpretable form) about what

the software system does, or what sequence of messages is

used to interact with it.

• All tasks associated with web services application

development have to be carried out by humans like discovery,

composition and invocation

• Problems of scalability

Vision of Semantic Web Services

Web[URI, HTML, HTTP]

Sta

tic

Dyn

am

ic

Syntax Semantic

Web Services[UDDI , WSDL, SOAP]

Semantic Web[RDF, OWL]

Semantic WebServices

Semantic Web Services

• Semantic Web Technology– Machine readable data

– Ontological basis

• Applied to– Web Services Technology• Reusable computational resources

• To automate all aspects of application development through reuse

Semantic Web Services Concepts

• Service– Service Provider & Requester

– Concrete Service • A specific performance of actions at a given time by one

party for another

– Service Description• A computational machine-readable representation of the

service, in terms of the value which it provides

• Abstract Service Description

• Concrete Service Description

S.W.S. Concepts[1]

• Agents

– Software components which represent the parties as

agents for the online presence as well as the

automated representation

• Service Provider Agent

• Service Requester Agent

– Act as representatives online on behalf of some party

S.W.S. Concepts[2]

• Communication– An online service interaction between the Service Provider Agent and

the Requester Agent to exchange of messages according to a certain protocol known by both the parties

• Choreography– A communication protocol among multiple parties during the

automated online services– Determines the constraints on the ordering of messages sent

• Grounding– One or more communication endpoints to send and receive the

messages according to some transport protocol

• Orchestration– A specification of an agent to provide type as well as sending time of a

message

S.W.S. Concepts[3]• Mediation

– Data Mediation• Consists of transforming from one syntactic format to another which may expect different

syntactic formats of the messages provided by different Service Provider Agents

– Ontology Mediation• Is used to make different choices based on the vocabulary when two parties describe

services• Reasoning

– One party is to reason with a description produced by the other party– Some additional reasoning will be necessary to translate between the two approaches

– Protocol Mediation• Reconciles the two different design of the interaction choreographies• Translating a message sequence into a different message sequence to accomplish the same

end

– Process Mediation• Reconciles the differences in the internal processes at the side of each party• The hardest form of mediation ( may impossible without engaging in process re-

engineering)

S.W.S. Concepts[4]

If the messages and choreographies are annotated semantically, then the mediation is possible automatically

S.W.S. Concepts[5]

• Life Cycle

S.W.S. Concepts[6]

• Service Modeling Phase

– Outset of the discovery phase

– Service Requester prepares a description of the

service what is interested in receiving

– Service Providers create abstract service descriptions

representing the service in which can be provided

S.W.S. Concepts[7]

• Service Discovery Phase– Matching• Compatibility of the requirement description and

the offer description

– Centralized Service Discovery• SMEP (Simple Message Exchange Protocol)

– During discovery, a requester may identify several providers which are potentially able to meet their needs

S.W.S. Concepts[8]

• Service Definition Phase– The conversation among the Service Requester

and one or more contacted as well as identified Service Providers

– Random Selection

– Analysis Selection

– Service Requester and Provider have agreed a service to be delivered, when the phase is successfully completed between two parties

S.W.S. Concepts[9]

• Service Delivery Phase– It can take place ;• Immediately • while after service definition has been completed• entirely off-line• involve communication between the two parties– It is again organized by an interaction choreography

by;» Service Delivery» Monitoring» Cancellation

Foundation Standards of Web Service

• Hypertext Transfer Protocol (HTTP)

– Communication Protocol to achieve interoperability via the web based on a set of standards built directly upon it regardless of their choice of platform or programming language

– Benefits:

• HTTP is everywhere

• Firewalls normally allow HTTP traffic


• Web Service Description Language (WSDL)– Is an XML-based language since ;• It is a pure text format• It is platform independent, • It can be easily parsed by any programming language• It is fairly easy to read

– Describes the service including the service name, functions, input and output parameters


• Simple Object Access Protocol (SOAP)– Its significant lies in its relationship with HTTP

– Platform and language independent based on XML

– Communication between applications via Internet

– format of the sending messages

– W3C recommendation

– Simple and extensible

– Allows to get around firewalls

SOAP

SOAP Request

SOAP Envelope

SOAP Response

SOAP Envelope


• Universal Description, Discovery and Integration (UDDI)

– UDDI is an XML-based standard for describing, publishing, and finding Web services.

– It is a specification for a distributed registry of Web services

– platform independent, open framework

– It can communicate via SOAP, CORBA, Java RMI Protocol

– It uses WSDL to describe interfaces to web services

– Open industry initiative

– Parts:• A registry of all a web service's metadata

• A set of WSDL port type definitions

Why add semantics to Web Services?

• Better Reuse– Semantic descriptions of services to help find relevant

services• Better Interoperability– Beyond syntax to semantics, mapping of data exchanged

between the services• Configuration/Composition– Enable dynamic binding of partners

• Some degree of automation across process lifecycle– Process Configuration– Process Execution

Foundation Standards of Semantic Web Services

• Semantic Annotation for WSDL and XML Schema (SAWSDL)– Standard finished in 2007

– Annotating WSDL with semantic information

– Built on existing Web Services standards using only extensibility elements

– Mechanism independent of the semantic representation language

– Provides means for mapping data between different Web Services

WSDL Description

Service

End

Poin

t

Brings

Faul

t

Faul

t Ref

.

Msg

Ref

.

Operation

Interface

Faul

t

Faul

t Ref

.

Msg

Ref

.

Operation

Types

Type

Defi

nitio

n

Elem

ent D

ecla

ratio

n

Ope

ratio

n St

yle MEP

Msg

. Lab

el

Schema MappingModel References


• SAWSDL– Extensibility attributes• modelReference

– Association between a WSDL component and a concept in some semantic model

– Annotations» WSDL components» WSDL Type Definitions

• liftingSchemaMapping– Mappings between WSDL Type Definitions and semantic data

• loweringSchemaMapping– Mappings between semantic data and WSDL Type Definitions


• SAWSDL

– Annotation of the operation element

• Carries a reference to a concept in a semantic model

that provides a high level description of the operation

– Annotation of the interface element

• Provides a reference to a concept or concepts in a

semantic model


• SAWSDL– Tools

• SAWSDL4J– Java API for manipulating and creating annotated SAWSDL

documents

• WSMO Studio– Semantic Web Service and Semantic Business Process modeling

environment

– Set of Eclipse plugins

• Radiant– WSDL-S/SAWSDL Annotation Tool

– Eclipse plug-in

OWL-S

• Ontology Web Language for Services• Represents an upper ontology for the description of

Semantic Web Services expressed in OWL• It is a Semantic Web Services description language,

expressed in OWL which describes the properties and capabilities of Web services

• Covers areas as; – Web services capability-based search and discovery,

– Specification of service requester and provider interactions

– Service execution

OWL-S Virtual Machine

• The OWL-S Virtual Machine (OVM) – A generic OWL-S processor – A generic execution engine– Executes the Process Model of a given service– During the execution, • processes inputs of Service Requester and outputs

returned by the Service Providers,• realizes the control and data flow of the composite

Process Model, • uses the Grounding to invoke WSDL based web services

when needed.

Monitoring[1]

• During the process model execution– What exactly should be monitored?

• Clear semantics of the process model

– Which model should be chosen? • Analyzing the process model and the grounding (It is possible to identify

important events that might be monitored)

– Event Types• Process Call• Inputs Assignment• Outputs Processing• Preconditions evaluation• (Conditional) result evaluation• Control construct execution• Grounding events• Failures and erroneous events

Monitoring[2]

• Event types are derived only from the logic of the process model and therefore can be used in any application

• Event types are neutral to the purpose for which they can be used

• Process Call– Start events are associated with input values and end events

additionally with produced output values and effects. – A simple and a composite process represent decomposition

of a process into subprocesses while an atomic process represents an execution of an existing web service operation

Monitoring[3]

• Inputs assignment– Input values of processes can be provided either

by the user (client) of the process model or by the data binding that is used

• Outputs Processing– Outputs of atomic processes are obtained as a

result of the service execution which is covered by the process call event type For simple and composite processes a new event type is needed to represent that the output value of the process is obtained from some output data binding

Monitoring[4]

• Preconditions evaluation– Represents process of the preconditions

evaluation with variables values assigned and with the true or false status

• (Conditional) result evaluation– Represents an evaluation of a result comprising

the grounded inCondition, produced effects and output bindings. A special event type represents a situation when no result can be applied which can be failed for all conditional results.

Monitoring[5]

• Control construct execution

– For each control construct one event type represents

its start and one its end

– For control constructs whose execution depends on an

expression evaluation (if-then-else, repeat-while,

repeat-until) the information representing this

expression evaluation and the branch chosen is

included in the starting event type

Monitoring[6]

• WSDL grounding events– Defines mappings of atomic processes to WSDL

operations and of inputs and outputs to WSDL messages and message parts

• Failures and erroneous events– For different categories of errors specific event

types are defined

Web Services Security Background

• Standards are proposed or accepted regarding authentication, encryption, and identity management

• RSA ,Hash Functions and Digital Signature Algorithms• Fundamental areas

– Message level protection– Message privacy– Parameter checking– Authentication– Authorization

• XML signatures• SAML – Security Assertion Markup Language

Web Services Security

• RSA– Used for any public/private key pair– Properties:• E(P, E(M,P)) M• E(P, E(M,P)) M

Where M is Sent Message and P is the Public Key

• Hash/Digest Functions– message dependent

• Digital Signature– Used for Authentication , Data Integrity and Non-

Repudiation

Message Level Protection

• Message Integrity

• A provider gets the hashed message which is

created by SHA-1 Algorithm , Then creates the

digest again and compares with the one from

the sender to verify the integrity of the

messages

Message Privacy

• Confidential Message• Message header has token and signature• Typically WS are chained together to form a

complex service• end-to-end encryption schemes unlike SSL• Solution: XML encryption

Parameter Checking

• Message validity

• To ensure the contents of a message are

appropriate to the service and well formed

• To prevent the SQL injection attack , look for

“ ; “ syntax

Authentication

• Verifying that the requester is who he/she

claims to be

• E.g. user name / password

• Send credential by issuing certificates to the

trusted authorities

Authorization

• Takes place after authentication and grantees the rights

of accessing

• Access Control Implementations

– Access matrix

– Access Control List (ACL)

– Role Based Access Control (RBAC)

Authorization (Access Control Implementations)

• Access matrix– Subject: An entity capable of accessing objects. The concept of

subject equates that of a process– Object: Anything to which access is controlled. E.g. files,

programs, segments of memory– Access right: The way in which an object is accesses by the

subject. Examples: read, write, and execute• Access Control List (ACL)

– Access matrix can be decomposed by columns, yielding access control lists

– For each object, it lists the users and their permitted access rights

– It may also have a default or public entry to covers subjects that are not explicitly listed

– Elements of the list may include individual as well group of users

Authorization (Access Control Implementations)

• Role Based Access Control (RBAC)(i) Reference model

• Objects, Operations, Permissions, Roles and Users (in-band artifacts)

(ii) System and Administrative model• System functionality, Administrative operations and reviews

• Permission to access a resource• Defines Roles and assigning permissions to RolesNOTE: OWL-S should map Users, Roles, Groups etc. to

the ontology

Conclusion of Semantic Web Services

• It is becoming an important and integral part of the Web (including intranets)

• It aims to provide an expressive, comprehensive framework for

– handling activities on the Web

– Enabling the use of agents on the Web

• Many tools and applications exist today; mostly prototype

• It is an active research area

• Strong interest and many paths to adoption also exist like the standards path

References• Introduction to the Semantic Web and Semantic Web Services, by Liyang Yu• Semantic Web Services Concepts, Technologies, and Applications by Rudi Studer, Stephan Grimm, Andreas

Abecker (Eds.)• J. Kopecky, C. Bournez, and E. Prud’hommeaux, “Semantic annotations forwsdl working group,” 2007

http://www.w3.org/2002/ws/sawsdl/• R. Akkiraju and B. Sapkota, “Semantic annotations for wsdl and xml schema usage guide,” 2007

http://www.w3.org/TR/sawsdl-guide/• K. Verma and A. Sheth, “Using sawsdl for semantic service interoperability,”2007.

http://lists.w3.org/Archives/Public/www-archive/2007May/att0081/SAWSDLSTC07-May21.pdf• “Sawsdl4j,” http://www.schneier.com/essay-037.pdf• “Wsmo studio,” http://www.wsmostudio.org• “Radiant,” http://lsdis.cs.uga.edu/• Adding Semantics to Web Services Standards, by Kaarthik Sivashanmugam, Kunal Verma, Amit Sheth, John Miller • SAWSDL: Semantic Annotations for WSDL and XML Schema, by Jacek Kopecky, Tomas Vitvar, Carine Bournez and

Joel Farrell• Semantic Web Services Monitoring: An OWL-S based Approach, by Roman Vaculín, Katia Sycara• Specifying and Monitoring Composite Events for SemanticWeb Services, by Roman Vaculín, Katia Sycara• Web Service Security Management Using Semantic Web Techniques, by Diego Zuquim Guimarães Garcia , Maria

Beatriz Felgar de Toledo• Authorization and Privacy for Semantic Web Services, by Lalana Kagal and Tim Finin, Naveen Srinivasan, and Katia

Sycara, SRI International