ServiceOriented Architecture

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Service-Oriented Architecture

• Chapter 17
• Fundamental WS- Extensions

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WS-Addressing language basics

• WS-Addressing is a core WS- extension providing
  features that can be used intrinsically or
  alongside features offered by other WS-
  specifications.
• The EndpointReference element
• This element is used by the From, ReplyTo, and
  FaultTo elements described in the Message
  information header elements section.

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WS-Addressing language basics

• WS-Addressing endpoint reference elements.

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WS-Addressing language basics

• Message information header elements
• This collection of elements can be used in
  various ways to assemble metadata-rich SOAP
  header blocks.
• WS-Addressing message information header elements

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WS-Addressing language basics

• WS-Addressing message information header elements

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WS-Addressing language basics

• WS-Addressing reusability
• Established generic set of extensions useful to
  custom service-oriented solutions.
• Also reusable by other WS- specifications

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WS-Addressing Summary

• WS-Addressing provides a collection of message
  header elements that can supplement a message
  with various (mostly routing-related) meta
  information.
• The WS-Addressing specification defines a set of
  reusable extensions that are becoming
  intrinsically commonplace among other
  WS-specifications.
• It is worth remembering that some of the message
  information header elements established by
  WS-Addressing are of type EndpointReference and
  can therefore be contain a variety of endpoint
  metadata.

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WS-ReliableMessaging language basics

• WS-ReliableMessaging introduces critical quality
  of service features for the guaranteed delivery
  or failure notification of SOAP messages.
• It also positions itself as a fundamental-
  extension, as show in Figure 17.2
• Key WS-ReliableMessaging language elements
• Sequence element
• MessageNumber element
• LastMessage element
• SequenceAcknowledgement element
• AcknowledgementRange element
• Nack element
• AckRequested element

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WS-ReliableMessaging language basics
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WS-ReliableMessaging language basics

• The Sequence, MessageNumber, and LastMessage
  elements
• Sequence construct resides in the SOAP message
  header to represent the location of the current
  message.
• In relation to the overall sequence of messages
  within which it is being delivered.
• Sequence relies on a set of child elements.
• Identifier element is used to contain an ID value
  associated with the sequence itself

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WS-ReliableMessaging language basics

• MessageNumber element contains a number that is
  the position of the message within the overall
  sequence order.
• LastMessage element can be added to the Sequence
  construct to communicate the fact that the
  current message is the final message of the
  sequence.

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WS-ReliableMessaging language basics

• The SequenceAcknowledgement and
  AcknowledgementRange elements
• SequenceAcknowledgement is issued by the
  recipient service upon the arrival of one or more
  messages with a sequence.
• The SequenceAcknowledgement header construct to
  communicate that the original delivery was
  successful.
• AcknowledgementRange element contains the Upper
  and Lower attributes that indicate a range of
  messages that were received.
• The Range is based on the MessageNumber values of
  the message.
• One AcknowledgementRange element communicates
  each consecutive set of messages received.
• Sequence construct resides in the SOAP message
  header to represent the location of the current
  message.

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WS-ReliableMessaging language basics

• The Nack element
• Communicates the delivery failure of a message.
• Its show which messages were not received.
• The AckRequested element
• RM source service can request that the RM
  destination send out a sequence acknowledgement
  message on demand by using the AckRequested
  header construct.

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WS-ReliableMessaging language basics

• Other WS-ReliableMessaging elements
• Additional WS-ReliableMessaging elements

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WS-ReliableMessaging Summary

• WS-ReliableMessaging introduces a set of elements
  that govern the processing of message sequences
  and subsequent delivery acknowledgments.
• WS-ReliableMessaging establishes the concept of a
  sequence, as implemented via the Sequence
  construct. This represents a group of messages to
  which additional delivery rules can be applied.
• WS-ReliableMessaging further introduces the
  concept of acknowledgements, as established by
  the SequenceAckowledgement and Nack elements,
  which provide an inherent mechanism for a
  guaranteed notification of successful and failed
  deliveries.

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WS-Policy language basics

• The WS-Policy framework establishes a means of
  expressing service metadata beyond the WSDL
  definition
• The WS-Policy framework is comprised of the
  following three specifications
• WS-Policy
• WS-PolicyAssertions
• WS-PolicyAttachments

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WS-Policy Relation to other WS- Specifications
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Policy Element

• Establishes the root construct to contain the
  various policy assertions that comprise the
  policy
• The WS-PolicyAssertions specification supplies
  the following set of common, predefined
  assertions elements
• TextEncoding Dictates the use of a specific
  text encoding format

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Policy Element cont

• Language Expresses the requirement or
  preference for a particular language
• SpecVersion Communicates the need for a
  specific version of a specification
• MessagePredicate Indicates message processing
  rules expressed using Xpath statements

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ExactlyOne Element

• Surrounds multiple policy assertions and
  indicates that there is a choice between them,
  but that one must be chosen

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All Element

• States that all of the policy assertions within
  the construct must be met

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Usage Attribute
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Preference Attribute

• Used to rank policy assertions in order of
  preference
• Assigned an integer value
• Higher value means a more preferred assertion
• Default value is 0

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PolicyReference Element

• A way to simply link an element with one or more
  policies
• Contains a URI attribute that points to one
  policy document or a specific policy assertion
  within the document
• Policy documents are merged at runtime when
  multiple PolicyReference elements are used within
  the same element

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PolicyURIs Attribute

• Can be used to link to one or more policy
  documents
• Added to an element and can be assigned multiple
  policy locations
• Policies are merged at runtime
• Example
• ltEmployee wspPolicyURIshttp//www.xmltc.com/
  tls/policy1.xmlEmp1
• http//www.xmltc.com/tls/policy2.xmlEmp2 /gt

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PolicyAttachment Element

• Associates a policy with a subject
• The child AppliesTo construct is positioned as
  the parent of the subject elements
• The PolicyReference element the follows the
  AppliesTo construct to identify the policy
  assertions that will be used

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Additional Types of Policy Assertions

• Policy assertions can be incorporated into WSDL
  definitions through the use of a special set of
  policy subjects that target specific parts of the
  definition structure
• A separate UsingPolicy element is provided for
  use as a WSDL extension
• WS-ReliableMessaging defines and relies on
  WS-Policy assertions to enforce some of its
  delivery and acknowledgement rules

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Additional Types cont

• WS-Policy assertions can be created to
  communicate that a Web service is capable of
  participating in a business activity or an atomic
  transaction
• A policy assertion can be designed to express a
  services processing requirements in relation to
  other WS- specifications
• WS-Policy assertions commonly are utilized within
  the WS-Security framework to express security
  requirements

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WS-MetadataExchange Language Basics

• Provides a standardized means by which service
  description documents can be requested and
  supplied.
• Supports interoperability and quality of service
  (QoS)
• Standardized metadata requests are
• GetMetadata
• Get

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WS-MetadataExchange Relation to other WS-
Specifications
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GetMetadata Element

• Placed in the Body area of a SOAP message
• Can be turned into a construct that hosts child
  Dialect and Identifier elements

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Dialect Element

• Specifies the type and version of the metadata
  specification requested
• Guarantees that the metadata returned to the
  service requesting it will be understood

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Identifier Element

• Narrows the criteria by asking for a specific
  part of the metadata

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Metadata, MetadataSection, and MetadataReference
Elements

• Used to organize the content of the message sent
  in response to a GetMetadata request
• Metadata
• construct resides in the SOAP message Body area
• MetadataSection
• constructs that each represent a part of the
  returned metadata
• Holds the contents of the metadata document
  returned

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Metadata, MetadataSection, and MetadataReference
Elements

• MetadataReference
• Holds the pointer to the document if that is all
  that is returned

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Get Message

• Used to explicitly request one of the documents
  from the location provided in the
  MetadataReference contstruct

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WS-Security Language Basics

• Provides extensions that can be used to implement
  message-level security measures
• Designed to work with any of the WS-
  specifications talked about so far
• Comprised of numerous specifications, many in
  different stages of acceptance and maturation

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WS-Security Relation to other WS- Specifications
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Security Element

• Represents the fundamental header block provided
  by WS-Security
• Can have a variety of child elements
• XML-Encryption
• XML-Signature
• WS-Security specification itself
• Can be outfitted with actor attributes that
  correspond to SOAP actor roles

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UsernameToken, Username, and Password Elements

• Can be used to host token information for
  authentication and authorization purposes
• Custom elements can be added, but the Username
  and Password child elements are typical children
  to this construct

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BinarySecurityToken Element

• Tokens stored as binary data
• Example
• Certificates

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SecurityTokenReference Element

• Allows a pointer to be provided to a token that
  exists outside of the SOAP message document

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EncryptedData Element

• Parent construct that hosts the encrypted portion
  of an XML document
• The Type attribute indicates what is included in
  the encrypted content

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CipherData, CipherValue, and CipherReference
Elements

• CipherData construct is required and must contain
  either a CipherValue element hosting the
  characters representing the encrypted text or a
  CipherReference element that provides a pointer
  to the encrypted values

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XML-Signature Elements
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XML-Signature Elements