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



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  • Web Services technologies are working towards an environment where organizations can make some of their abilities accessible via the Internet. Web Service technology provides a standard and widely accepted way of defining these interfaces
  • This is done by ‘wrapping’ some computational capability with a Web Service interface, and allowing other organizations to locate it (via UDDI) and interact with it (via WSDL). Hence, Web Service technology allows the description of an interface in a standard way,
  • Scalability in expansion of scaling the capabilities in geographic location scale in administration of scaling
  • The Semantic Web Services vision is to combine Web Services as well as Semantic Web technologies and through this to enable automatic and dynamic interaction between software systems.
  • We can annotate software being offered via Web Service interfaces with machine interpretable descriptions describing what and how the software does (namely the service it provides a potential user). Furthermore, with ontologies able to describe the services that can be provided, we can bring about ‘advertising’ of services in a way which is both rich and machine-interpretable. This allows more sophisticated discovery of services than is currently possible with UDDI.
  • Service-Providerprovides a service to a Service-Requester when the first party does something for the benefit of the secondTo describe services, the Semantic Web approach uses techniques based on knowledge representationService Description : When describing a service, there are two key design decisions which must be made initially. First, what formal language is going to be used to describe it? Should it be described using horn clause logic, description logic, non-monotonic logic or some other approach?Secondly, what specific concepts and relations are going to be permitted in descriptions? what is the meaning of these?
  • Hence, the agent property is a role the component takes, rather than some intrinsic property of the component.Often, they will be reactive not proactive, and will be hardwired to follow some pre-determined process.
  • Grounding : When two parties engage in a conversation, they must each have one or more communication endpoints to send and receive the messages according to some transport protocol. This is referred to as the grounding of the choreography.Orchestration :NOTE: the choreography specifies what is permitted of both parties, while an orchestration specifies what each party will actually do.
  • Reasoning : if one party is to reason with a description produced by the other party, then some additional reasoning will be necessary to translate between the two approaches. This additional reasoning is termed ontology mediationProtocol : Two components which are to interact with each other may each have been designed with a particular interaction choreography in mind. Unless agreement was reached between the two designers (either directly or indirectly through the adoption of a standard) then it is unlikely that the two choreographies will be identical. Process :Behind any interaction, each party has some internal process which manages the reasoning and resources necessary to bring about that interaction. Like business processIn some cases, even though the two parties are able to interact via some protocol, there may be some difference between their processes which means this interaction will not succeed.
  • It is key to enabling service interaction to take place automatically
  • Because all details of the service will be known at the outset (e.g., the provider of the service is not known, and the cost of the service may not be known), the description will be of an abstract service. This abstract service description makes up the service requirement description of the service requester.
  • Centralized Service Discovery:The most common Centralized Discovery ‘Service’ is a which is contacted by the requester using a Simple Message Exchange Protocol
  • Random And Analysis Selection: the Selection of which to contact may simply be random, or may involve some analysis of the service providers and choice of which appear in some sense ‘best’
  • 1-When the definition of a service has been agreed, then service delivery can take place ……End: If communication takes place, this is again governed by an interaction choreographyService delivery choreography : covers the exchange of messages associated directly with the delivery of the serviceMonitoring choreography : covers the exchange of messages which allow the service requester to receive information regarding the progress of the service from the providerCancellation/renegotiation choreography: allows the service requester, in certain circumstances, to cancel or alter the service which they are receiving from the provider
  • HTTP is everywhere — any machine that can run a Web browser supports HTTP because a Web browser’s protocol is HTTP.Firewalls normally allow HTTP traffic; in other words, you can use HTTP to talk to any machine.
  • WSDL : In other words, it is an advertisement of the service you provide. .
  • It defines a standard protocol specifying how one application should communicate and exchange data with another one over the Internet
  • UDDI is an open industry initiative enabling businesses to discover each other and define how they interact over the Internet.Parts: i) A registry of all a web service's metadata including a pointer to the WSDL description of a serviceii) A set of WSDL port type definitions for manipulating and searching that registry
  • Process Configuration (Discovery and Constraint analysis)Process Execution (Addressing run time heterogeneities like data heterogeneities.)
  • The Web Services Description Language (WSDL) with Semantic Annotations for WSDL and XML Schema (SAWSDL). The figure shows WSDLcomponents and the SAWSDL annotations that point to semantic concepts for specifying semantics or to schema mappings of data transformations
  • WSDL components (Interfaces, Operations, Faults)WSDL Type Definitions (Simple/ Complex types, Element/ Attribute declarations)
  • Annotation of the operation element specifies its behavioral aspects or includes other semantic definitionsAnnotation of the interface elementdescribes the Interface
  • A tool for execution of OWL-S web services must be able to interpret the Process Model of the service according to its semantics and provide a generic mechanism for invocation of web services represented as atomic processes in the Process Model. OWL-S processor that allows Web services and clients to interact on the basis of the OWL-S description of the Web service and OWL ontologiesexecution engine which can be used to develop applications that need to interact with OWL-S web servicesExecutes the Process Model by going through the Process Model while respecting the OWL-S operational semantics and invoking individual services represented by atomic processes.
  • Process Call Presents probably the most important event type. For each process type specific event types are defined representing its start and end.
  • Process Call Presents probably the most important event type. For each process type specific event types are defined representing its start and end. output data binding means the dataflow of the process model specifies that the output is produced by some previous processes).
  • NOTE : This is application layer security (not network layer security)
  • XML encryption allows for encryption of any combination of the message body, header, attachments, and sub-structures
  • SQL injection is a common malicious code. Typical identification method is to look for “;’ (semicolon) that allows for SQL commands to follow.
  • If the sender previously unknown: send credential to verify oneself.
  • In any organization, data located may have levels of sensitivity
  • Access Matrix A general model of access control as exercised by a file or database management system is that of an access matrix
  • handling activities on the WebEnables greater automation of discovery, selection, invocation, composition, monitoring, and other service management tasksEnabling the use of agents on the WebSimplicity and widespread adoption of WS building blocks are enablers


  • 1. Semantic Web Services
    (Standards, Monitoring, Testing and Security)
    Department of Engineering-Information Technology
    Presented by : Reza Ghanbari
  • 2. Outline
    Introduction of Web Service
    Semantic Web Services
    Life Cycle
    Foundation Standards of Web Service
    Foundation Standards of Semantic Web Service
    OWL-S Virtual Machine
    Monitoring of Semantic Web Service
    Security of Semantic Web Service
    Message Level Protection
    Message Privacy
    Parameter Checking
    Conclusion of Semantic Web Services
  • 3. Web Service
    • A program programmatically accessible over standard internet protocols
    • 4. Loosely coupled, reusable components
    • 5. Encapsulate discrete functionality
    • 6. Distributed
    • 7. Add new level of functionality on top of the current web
  • Web Services Framework
  • 8. 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
  • 9. Vision of Semantic Web Services
  • 10. 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
  • 11. Semantic Web Services Concepts
    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
  • 12. S.W.S. Concepts[1]
    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
  • 13. S.W.S. Concepts[2]
    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
    A communication protocol among multiple parties during the automated online services
    Determines the constraints on the ordering of messages sent
    One or more communication endpoints to send and receive the messages according to some transport protocol
    A specification of an agent to provide type as well as sending time of a message
  • 14. S.W.S. Concepts[3]
    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
    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)
  • 15. S.W.S. Concepts[4]
    If the messages and choreographies are annotated semantically, then the mediation is possible automatically
  • 16. S.W.S. Concepts[5]
    Life Cycle
  • 17. 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
  • 18. S.W.S. Concepts[7]
    Service Discovery Phase
    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
  • 19. 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
  • 20. S.W.S. Concepts[9]
    Service Delivery Phase
    It can take place ;
    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
  • 21. 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
    HTTP is everywhere
    Firewalls normally allow HTTP traffic
  • 22. Foundation Standards of Web Service
    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
  • 23. Foundation Standards of Web Service
    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
  • 24. SOAP
  • 25. Foundation Standards of Web Service
    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
    A registry of all a web service's metadata
    A set of WSDL port type definitions
  • 26. 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
    Enable dynamic binding of partners
    Some degree of automation across process lifecycle
    Process Configuration
    Process Execution
  • 27. 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
  • 28.
  • 29. Foundation Standards of Semantic Web Services
    Extensibility attributes
    Association between a WSDL component and a concept in some semantic model
    WSDL components
    WSDL Type Definitions
    Mappings between WSDL Type Definitions and semantic data
    Mappings between semantic data and WSDL Type Definitions
  • 30. Foundation Standards of Semantic Web Services
    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
  • 31. Foundation Standards of Semantic Web Services
    Java API for manipulating and creating annotated SAWSDL documents
    WSMO Studio
    Semantic Web Service and Semantic Business Process modeling environment
    Set of Eclipse plugins
    WSDL-S/SAWSDL Annotation Tool
    Eclipse plug-in
  • 32. 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
  • 33. 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.
  • 34. 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
  • 35. 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
  • 36. 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
  • 37. 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.
  • 38. 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
  • 39. 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
  • 40. 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
    XML signatures
    SAML – Security Assertion Markup Language
  • 41. Web Services Security
    Used for any public/private key pair
    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
  • 42. 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
  • 43. 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
  • 44. 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
  • 45. 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
  • 46. 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)
  • 47. 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
  • 48. Authorization (Access Control Implementations)
    Role Based Access Control (RBAC)
    Reference model
    Objects, Operations, Permissions, Roles and Users (in-band artifacts)
    System and Administrative model
    System functionality, Administrative operations and reviews
    Permission to access a resource
    Defines Roles and assigning permissions to Roles
    NOTE: OWL-S should map Users, Roles, Groups etc. to the ontology
  • 49. 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
  • 50. 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
    R. Akkiraju and B. Sapkota, “Semantic annotations for wsdl and xml schema usage guide,” 2007
    K. Verma and A. Sheth, “Using sawsdl for semantic service interoperability,”2007.
    “Wsmo studio,”
    Adding Semantics to Web Services Standards, by KaarthikSivashanmugam, KunalVerma, AmitSheth, John Miller
    SAWSDL: Semantic Annotations for WSDL and XML Schema, by JacekKopecky, Tomas Vitvar, CarineBournez and Joel Farrell
    Semantic Web Services Monitoring: An OWL-S based Approach, by Roman Vaculín, KatiaSycara
    Specifying and Monitoring Composite Events for SemanticWeb Services, by Roman Vaculín, KatiaSycara
    Web Service Security Management Using Semantic Web Techniques, by Diego ZuquimGuimarães Garcia , Maria Beatriz Felgar de Toledo
    Authorization and Privacy for Semantic Web Services, by LalanaKagal and Tim Finin, NaveenSrinivasan, and KatiaSycara, SRI International
  • 51. Thank You !