Policy Support for Businessoriented Web Service Management

1
Policy Support for Business-oriented Web Service
Management
Stephen Gorton and Stephan Reiff-Marganiec
Latin-American Web Congress, Cholua, Mexico,
25-27 October 2006
Department of Computer Science, University of
Leicester University Road, Leicester LE1 7RH
United Kingdom
2
SENSORIA

• Software Engineering for Service-oriented Overlay
  Computers
• IST project funded by the EU
• http//sensoria.fast.de
• The aim of SENSORIA is to develop a novel
  comprehensive approach to the engineering of
  software systems for service-oriented overlay
  computers where foundational theories, techniques
  and methods are fully integrated in a pragmatic
  software engineering approach.
• Work Package 1 Service Description
• Task 1.3 Service-oriented business modelling

3
Outline

• Service oriented computing and web services
• Service management
• Introduction to policies
• The Appel PDL
• Appel in telecommunications
• How we use policies
• The process execution engine
• Specifying requirements
• Example usage
• Further and related work
• Summary and conclusions

4
SOC and web services

• Services are
• Loosely coupled units of software available over
  a network, exposed by well-defined interfaces
• Based on open standards
• Composable, i.e. you can orchestrate two or more
  together to make a composite service.
• Web services
• A popular implementation of SOA, incorporating
  open standards such as XML
• Are also optionally self-describing and
  discoverable
• Communicate via standard HTTP.
• Service-oriented computing (SOC) is an
  architectural
• approach to building loosely coupled
  applications.
• The link with telecommunications
• Internet telecommunications based on components
  or features
• Features include call forwarding, call waiting,
  etc.
• SOC is similar in the sense of component
  composition
• Can we use telecoms technology for SOC?

Feature FA
Service SA
Feature FC
Service SC
Feature FB
Service SB
5
Service management

• Present
• Not huge uptake in WS
• Lots of large implementations
• Relatively few open access services
• Amazon, Ebay and Google provide public WS
  interfaces.
• Future
• Lots of WS?
• Smaller WS capable of doing more atomic
  activities?
• Composition of WS provides required
  functionality.
• Business needs
• Align IT objectives with business objectives
• Adaptability and flexibility of systems
• Business-oriented management?
• As a substantial number of Web Services become
  available, so the
• attention shift will be from service
  infrastructure to service management.
• Casati et al. Business-oriented management of Web
  Services. Comm. ACM, 46(10)55-60, 2003.

6
Policies and web services

• Policies are
• information that can be used to modify the
  behaviour of a system.
• (Lupu and Sloman. Conflicts in Policy-based
  Distributed Systems Management.
• IEEE Transactions on Software Engineering, Nov
  1999.
• Policy Examples
• WS-Policy
• Including WS-PolicyAttachment
• Access control
• Ponder
• KAoS
• Rein
• XACML
• WSPL
• Automatic negotiations
• Lamparter and Agarwal. Specification of policies
  for automatic negotiations of web services.
• In L. Kagal, T. Finin and J. Hendlerm editors,
  SWPW, 2005.
• Our policies are

7
Appel policy framework

• The Accent Project Policy Environment/Language
• A Policy Description Language (PDL), allowing
  users to write their own policies
• Designed by Reiff-Marganiec et al at the
  University of Stirling
• S. Reiff-Marganiec, K. Turner and L. Blair.
  Appel The Accent policy environment/language.
  Technical report CSM-164, University of Stirling,
  Jun 2005.
• Developed for the Accent project
  (telecommunications control).
• PDL allows for the definition of ECA policies or
  goals
• Appel defines an XML Schema based around
• Triggers
• Conditions
• Actions
• Extended by functions
• Prompt
• to get information from the user
• Display
• to output data in some visual format

8
Where policies fit in
9
The proposed architecture
10
The management runtime engine
Full Composition
Correctness
Task Map
Workflow
Stubless Composition
Skeleton Composition
Conflict
Policies
Mediator
Mediator
Discovery Engine
Mediator
Mediator
Mediator
Mediator
Mediator
Mediator
services located and composed using UDDI, WSDL,
etc. or equivalent
WS
WS
WS
11
Appel policies

• Triggers (adapted from the SENSORIA ontology)
• Message events
• Time events
• Change events
• Service events
• Interaction events
• Conditions
• Checks on local or remote data values
• Includes standard mathematical operators
• Actions
• Core information in the policy
• Defines what service to invoke via different tags
• Can specify more than one action with tags ltandgt,
  ltandthengt, ltelsegt, ltorgt, or ltorelsegt

ltpolicy gt ltpreferencegt ltpolicyrulegt
lttriggersgt lttriggergt lttriggergt
lt/triggersgt ltconditionsgt ltconditiongt
ltconditiongt lt/conditionsgt
ltactionsgt ltandthen /gt ltactiongt
ltactiongt lt/actionsgt lt/policyrulegt lt/polic
ygt
12
Uses in telecommunications

• Forward incoming calls
• Emergency call handling
• Announcing availability
• Using capability
• Controlling registration.
• Example If Ken is busy, forward his incoming
  calls to Bob

ltpolicy ownerken_at_cs.stir.ac.uk
applies_token_at_cs.stir.ac.uk idForward if
busy enabledtrue changed2004-08-02T112005
gt ltpolicy_rulegt lttriggersgt ltand /gt
lttriggergtconnect_incominglt/triggergt
lttrigger arg1gtunavailable(arg1)lt/triggergt
lt/triggersgt ltaction arg1bob_at_cs.stir.ac.ukgtf
orward_to(arg1)lt/actiongt lt/policy_rulegt lt/policy
gt
13
How can we use policies?

• Express preferences
• I will only fly with British Airways on flights
  lasting over 8 hours
• Given a choice, I prefer to use a supplier in my
  phone book
• Options
• Modalities include must, should, prefer, and
  their negations.
• Express requirements
• Purchase a rail ticket from X to Y, with times T
  and S
• Quote for a holiday
• Options
• Unbounded on what we can express
• Restrictions are on classifications of
  requirements (tags).
• Express restrictions
• Services not allowed from originating country X
• Capping the maximum expense claim amount

14
Specifying requirements 1
ltmessagegt ltsourcegt lt/sourcegt ltdestinationgt
lt/destinationgt ltdescriptiongt ltdescriptiongt
ltdatagt lt/datagt lt/messagegt

• Local functionality
• System messaging
• (more applicable to triggers)

ltserviceTypegt ltdomaingt lt/domaingt
ltsubdomaingt lt/subdomaingt lt/serviceTypegt

• Service classification
• Domain, subdomain

• Service functionality
• Inputs
• Preconditions
• Postconditions
• Outputs
• Exceptions
• Side effects

ltfunctionalitygt ltinputsgt ltinputgt
ltinputgt ltpreconditiongt conditions
ltpostconditiongt conditions ltoutputsgt
ltoutput typelistgt display(this) ltexception
namedefaultgt function() lt/exceptiongt
ltsideEffectsgt ltpenaltygt ltbonusgt
lt/sideEffectsgt lt/functionalitygt
15
Specifying requirements 2

• Quality
• Any identified qualitative value can be
  addressed, provided it is published in the
  directory entry (UDDI or similar), or it is
  testable
• Qualitative checks based on similar condition
  checks
• Named parameters compared against values
• Operators include
• Equal to
• Less than
• Less than or equal to
• Greater than
• Greater than or equal to

ltqualitiesgt ltqualitygt ltparametergtpricelt/para
metergt ltoperatorgtleqlt/operatorgt
ltvaluegt0lt/valuegt lt/qualitygt lt/qualitiesgt
16
Example usage train tickets
ltpolicy ownerstephen_at_mcs.le.ac.uk
applies_to_at_mcs.le.ac.uk idQuery for
cheapest train ticket (UK) enabledtrue
changed2006-05-08T155100gt
ltpreferencegtmustlt/preferencegt ltpolicy_rulegt
lttriggergt ltmessagegt
ltdatagtstartlt/datagt lt/messagegt lt/triggergt
ltconditiongt ltparametergtlocationlt/parametergt
ltoperatorgteqlt/operatorgt
ltvaluegtUKlt/valuegt lt/conditiongt
ltaction arg1promptUser(Departure Station)
arg2promptUser(Arrival Station)
arg3promptUser(Date of Travel)
arg4promptUser(Fast or Cheap)
arg5promptUser(Railcard)gt
ltserviceTypegt ltdomaingtTravellt/domaingt
ltsubdomaingtTicket Vendorlt/subdomaingt
lt/serviceTypegt Further actions
17
Example usage functionality specification
ltfunctionalitygt ltinputsgt ltinput
namefromgtfrom(arg1)lt/inputgt ltinput
nametogtfrom(arg2)lt/inputgt ltinput
namedategtfrom(arg3)lt/inputgt ltinput
namepreferencegtfrom(arg4)lt/inputgt
ltinput namerailcardgtfrom(arg5)lt/inputgt
lt/inputsgt ltpostconditionsgt
ltpostcondgt ltoutputgt ltor /gt
lttypegtlistlt/typegt
lttypegtemptylt/typegt lt/outputgt
ltpostcondgt lt/postconditionsgt
ltoutputsgt ltoutput typelistgtdisplay(this
)lt/outputgt ltoutput typeemptygtdisplay_em
pty()lt/outputgt lt/outputsgt
ltexceptionsgt ltexception
namedefaultgtdisplay_exception(this)lt/exceptiongt
lt/exceptionsgt ltsideEffectsgt
ltpenaltygt lttypegtdefaultlt/typegt
ltpermissiongtdisallowlt/permissiongt
lt/penaltygt ltbonusgt
lttypegtdefaultlt/typegt ltpermissiongtallowlt/
permissiongt lt/bonusgt
lt/sideEffectsgt lt/functionalitygt
18
Example usage quality specification
ltqualitiesgt ltqualitygt
ltparametergtpricelt/parametergt
ltoperatorgtleqlt/operatorgt
ltvaluegt0lt/valuegt lt/qualitygt
ltqualitygt ltparametergtavailabilitylt/param
etergt ltoperatorgteqlt/operatorgt
ltvaluegtnowlt/valuegt lt/qualitygt
lt/qualitiesgt invokeService(functionality,
quality) lt/actiongt lt/policy_rulegt lt/policygt
19
Further work

• Domain restriction or classification
• Interaction of policies with task maps
• Refinement of policy functions and definition of
  further functions
• Mediation of user-defined and service requested
  data types
• Integration of this technology with service
  coordination technology
• Mapping of task maps to workflow languages (e.g.
  YAWL)
• Related work
• Task maps
• SRML
• YAWL

20
Summary and Conclusions

• With increasing numbers of web services,
  management will shift further into the business
  domain
• Management of software will shift closer to the
  business analyst rather than the software
  engineer
• Align IT objectives with business objectives.
• Similarities between telecoms and SOC
• Feature composition
• Management issues.
• Appel extended as a PDL for SOC
• Users define their own policies to express goals,
  requirements and preferences
• Extension functions allow us to address the SOC
  domain.
• Trivial example of purchasing a ticket.
• Questions?