Web Services and Semantic Web Services: DAML-S and WSMF

1
Web Services and Semantic Web Services DAML-S
and WSMF

• 21st-26th July 2003
• Cercedilla (Spain)
• Federica Schiappelli
• Francesco Taglino

2
Summary

• Web Services and Semantic Web Services
• DAML-S
• WSMF
• Conclusions

3
Web Services and Semantic Web Services
4
What is a Web Service? IBM

• Web was designed primarily for human
  interpretation and use
• Web services are a new breed of Web application
• self-describing
• modular applications that can be published,
  located, and invoked across the Web.
• Web services perform functions, which can be
  anything from simple requests to complicated
  business processes.
• In other words, web services are interoperable
  building blocks for constructing applications.

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Web Services an example
Authentication
Inter-library loan request
Document Translation
Search
Payment
Internet
Digital Library Application

• The current web enables
• enables users to connect to applications
• The web services architecture enables
• applications to connect to other applications
  (from B2C to B2B).

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The web service architecture
Service Registry
Service Requestor
Service Provider
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Overview of web services standards

• Data and Control Flow description of Web
  Services Security and Management
• A mechanism for registering and looking up web
  services
• Programmatic way of describing the Web Services
  Interface
• Web Services Communication protocol

WS-Security WS-Routing etc
WSDL
BPEL4WS
UDDI
XML
WSDL
SOAP
HTTP
8
A case of too many proposals?

• Many other Web Services Proposals exist
• Transport
• DIME Direct Internet Message Encapsulation
• HTTPR Reliable HTTP
• Packaging Extensions
• SOAP-DSIG SOAP Security Extensions Digital
  Signature
• SWASOAP Messaging with Attachments
• WS-License Web Services License Language
• WS-Referral Web Services Referral Protocol
• WS-Routing Web Services Routing Protocol
• WS-Security Web Services Security Language

Source Pavel Kulchenko http//www.xml.com/pub/a
/2002/01/09/soap.html?page1
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A case of too many proposals?

• Other Web Services Proposals exist
• Description
• BPEL4WS Business Process Execution Language For
  Web Services
• WSCM Web Services Component Model
• WSFM Web Services Modeling Framework
• WSML Web Service Meta Language
• WSOL Web Service Offering Language
• WSXL Web Service Experience Language
• WSUI Web Service User Language
• XLANG Web Service Offering Language
• Discovery
• USML UDDI Search Markup Language
• WS-Inspection Web Service Inspection

Source Pavel Kulchenko http//www.xml.com/pub/a
/2002/01/09/soap.html?page1
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Towards the Semantic WS

• Web Service benefit from inclusion of semantics
• For example, DAML - DARPA Agent Markup Language
  was designed to provide ontologies and
  description logics for Agent Markup to improve
  interoperability
• Semantic Web provides open, extensible, semantic
  framework for describing and publishing semantic
  content
• Benefits?
• Improved interoperability
• Automated service composition, discovery and
  invocation
• Access to knowledge on the internet

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Tackling Semantic Interoperability

• Semantic Interoperability is a major hurdle for
• Locating Services
• Different terms used for advertisements and
  requests
• Negotiating contracts communications
• Different protocols used by different communities
  when agreeing whether to transact
• Invoking
• Constructing valid messages based on the
  published signature/interface of a service
• Understanding
• Interpreting the results of invoking a service
• Composing Services
• Constructing plans to achieve meta-goals based on
  available Services/Agents

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Example of Semantic Mismatch

• at the Content Level
• Provider returns value Pennsylvania, but
  requester only understands two letter state codes
  (i.e. PA)
• at the Attribute level
• Requester needs rainfall but provider provides
  precipitation
• at the level of Units of Measure
• Requester has value in inches, but provider
  requires cm
• at the Message level
• Requester has length width, provider requires
  area

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DAML-S
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What is DAML-S?

• DAML-S A DARPA Agent Markup Language for
  Services
• A DAMLOIL ontology for describing properties
  capabilities of agents (Web) services in an
  unambiguous, computer interpretable mark-up
  language.

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DAML-S Upper Ontology

• input types
• output types
• preconditions
• postconditions

• communication protocol (RPC, HTTP, )
• port number
• serialization

• process flow
• composition hierarchy
• process definitions

Source Terry Payne, University of Southampton
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Describing the Service Profile

• A profile represents a functional description of
  the service capabilities
• Describe
• Dataflow properties
• Inputs required to invoke the service
• Outputs that are generated by the service
• World-State properties
• Preconditions that should be satisfied
• Effects that will be asserted if the service
  execution is successful
• Service metadata is presented
• Determine additional data that should be used
  when searching for, or selecting services
• Identify whether the profile description is an
  instance of existing service categories (profile
  hierarchy)

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The Service Profile (what it does)
Non Functional Properties
Functionality Description
Source Terry Payne, University of Southampton
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The Profile properties

• Non Functional
• Provide supporting information about services
  (i.e., serviceName, textDescription, )
• Functional
• Functional specification of what the service
  provides in terms of parameters
• Preconditions set of conditions that should hold
  prior to service invocation (i.e., Credit Card is
  valid)
• Inputs set of necessary inputs that the equester
  should provide to invoke the service (i.e.,
  Credit Card number)
• Outputs results that the requester should expect
  after interaction with the service provider is
  completed (i.e., Flight booking number)
• Effects set of statements that should hold true
  if the service is invoked successfully (i.e.,
  Credit Card being debited)

Source Terry Payne, University of Southampton
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Decribing the Service Process Model

• A process model represents a service as a
  workflow, consisting of several processes
• Each process could itself be another service, a
  workflow, or an atomic process
• Identify and define the atomic processes
• what are its inputs and outputs.
• Are there any preconditions that should be met,
  or effects that are generated?
• Define the workflow that coordinates the
  execution of these processes

Source Terry Payne, University of Southampton
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The Service Process Model (how it works)
Source Terry Payne, University of Southampton
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Describing the Service Grounding

• Provide a WSDL file for the service being
  described
• Identify and map
• The atomic processes within the process model to
  the corresponding operations in the WSDL
  description
• The inputs outputs correspond to WSDL messages

Source Terry Payne, University of Southampton
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The Service Grounding (how to access it)
Source Terry Payne, University of Southampton
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Publication
Profile
Discovery
Simulation

Selection
Process Model
Verification
Composition

Invocation, Interoperation
Grounding

Monitoring, Recovery
Development Deployment Use
Source David Martin for DAML-S Coalition
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DAML-S tools

• Web Service Composer semi-automatic process for
  dynamic composition of ws http//www.mindswap.org/
  evren/composer/
• WSDL2DAML-S Converter complete for Grounding,
  partial for Profile http//www.daml.ri.cmu.edu/wsd
  l2damls
• DAML-S Matchmaker web service that helps to make
  connections between service requesters and
  service providers http//www.damlsmm.ri.
  cmu.edu/

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WSMF
Source Dieter Fensel (University of Innsbruck)
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What is the WSMF

• WSMF Web Services Modeling Framework provides a
  framework for peer-to-peer communication between
  any number of endpoints (i.e., anything that can
  be invoked and responds)
• Strong de-coupling
• Each endpoint is fully autonomous in its message
  exchange behaviour and message content
• Strong mediation
• Extensive support for bridging data and process
  differences resulting from strong de-coupling
  (compensating strong decoupling)

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Main elements

• Ontologies
• Goal/Capability repositories
• Web Services
• Mediators

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Ontologies

• Definition in context of basic communication
  elements
• Document types
• Structure of data communicated
• Semantics
• Meaning of data communicated
• Both are defined by endpoints due to their
  autonomy
• Definition in context of WSMF
• Goal and pre-/post-condition support
• Meaning of goal web service provider addresses
• Meaning of goal web service client has in mind
• This is defined by endpoints due to their autonomy

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Capability Repositories

• Capability
• Client can state goal it has, i. e. what it tries
  to accomplish
• E. g. book a complete round-trip travel
• Endpoint can state goal it addresses, i. e. for
  what goal it provides service
• E. g. book most expensive hotels
• E. g. book affordable hotels -)
• Ontology
• E. g. definition of round-trip travel
• Trip between two cities whereby transportation is
  between the two cities. One destination city and
  one origination city. Complete means flight,
  hotel and car whereby flight is between the two
  cities and hotel and car are booked in the
  destination city.

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Capability Repositories (2)

• Pre-conditions
• Input that web service requires to function
  properly
• E. g. definition of affordable or most
  expensive
• Ontology
• What does affordable mean?
• Total charge per night per room (including taxes
  and any applicable fees) is in the range of USD
  49 to USD 99
• Most expensive is clear -)
• Select the hotel in the city with the highest
  price per room per night

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Capability Repositories (3)

• Post-condition
• Output web service provides
• E. g. a complete trip is booked or not at all
• Ontology
• What does booked mean?
• Flight in status OK, hotel guaranteed with credit
  card for late arrival, car guaranteed with credit
  card.
• What does not at all mean?
• No flight booked or reserved, no hotel booked or
  reserved, no car booked or reserved and no
  financial transaction or obligation existent (or
  any more, if cancellation fees have been paid)

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Web Services definition

• Name
• Reference to goal and pre/post cond.
• Input/Output data
• Data flow (i.e., split, join, typecast)
• Control flow (i.e., sequence, conditional
  branching, for/while-loops, parallel exec.)
• Compensation (i.e., undoing, side effects)

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Mediation

• Data Mediation
• Data matching (lossless transf.)
• Data mismatching (lossy transf.)
• Data-overcomplete mismatch
• Data-incomplete mismatch
• Semantic mismatches
• Process Mediation
• Precise match
• Message sent by sender is expected by receiver
• Unresolvable mismatch
• Message sent by sender are not expected by
  receiver
• If message cannot be consumed, merger,
  re-arranged or artificially produced
• Resolvable mismatch

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Conclusions
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Conclusions

• DAML-S is an ontology for describing properties
  capabilities of Web services
• WSMF defines description elements for
• adding semantics to WS
• providing WS as a scalable infrastructure for
  eWork and eCommerce
• They are complementary
• DAML-S could be used for defining a formal
  semantics but
• it lacks many of the modeling primitives
  important within WSMF
• it does not provide formal semantics for many of
  the primitives expressed in it