Features, Properties and Bindings

1
Features, Properties and Bindings

• Glen Daniels, Macromedia
• November 15th, 2002

2
A Brief History of Features

• SOAP HTTP binding is natively req-resp
• Req-resp is also something you can do over other
  protocols by using SOAP extensibility
• SOAP 1.2 needed a way of describing the semantics
  which are provided by protocol bindings, and
  which could also be implemented with headers

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Whats a Feature?

• Arbitrary piece of semantics / functionality
• Abstractly described in a spec
• Named with a URI
• We can talk about it / point to it
• Other specs can refer to the SAME thing

4
Features Have Properties

• Properties are like the API of a feature
• Named with URIs (used to be Qnames)
• Typed with XML schema
• Example
• TrafficLight feature has color property,
  which is an enum red, yellow, green
• Feature spec says the value of this property
  should be passed from node to node, but NOT how
  it should be done

5
Bindings Implement Features

• The specification of a binding includes a
  description of which (if any) features that
  binding provides
• Examples
• The SOAP HTTP binding natively implements the
  Request-Response MEP
• A SOAP HTTPS binding might natively implement a
  secure-channel feature

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Modules Implement Features

• Reminder Modules are semantics / functionality
  implemented within the SOAP envelope (headers)
• A SOAP Module specification indicates which (if
  any) features that Module provides
• Examples
• An encryption Module might implement a
  secure-channel feature
• A correlation Module might implement the
  Request-Response MEP

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Example Diagram
Feature http//secureChannel Properties NONE
Binding http//https-binding Implements http
//secureChannel
Module http//mySecurityExt Implements http//
secureChannel
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Example 2 Properties

• Feature urnEncryption
• Property urncipher
• Spec says sending node MUST ensure the cipher
  value is available to the receiving node.
• When implemented as a Module
• ltsoapheadergt ltsecciphergtBLOWFISHlt/secciphergt
  lt/soapheadergt
• When in a Binding
• Cipher could be a protocol header, or simply a
  fixed value

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Describing Modules

• ltsoapheadergt isnt expressive enough
• Cant do state/context dependent headers
• ltsoapmodulegt lets us say follow the rules of
  the Module spec
• Properties can be constrained/given values in WSDL

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Describing Features

• ltsoapfeaturegt has been proposed, but features
  can be more than just SOAP
• ltwsdlfeaturegt is better
• Can describe abstract features / requirements /
  policies in the interface

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Describing Features,cont.

• ltsoapbindinggt
• ltsoapfeature urihttp//correlation-feature
• soaprequiredtrue/gt
• ltsoapproperty urihttp//myPropertygtValuelt/gt
• ltsoapproperty urihttp//property2
• typemyNSrestrictedType/gt
• ltsoapmodule urihttp//CorrelationModule/gt
• lt/soapbindinggt

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Proposal

• This extensibility / composability framework is
  architectural, and gets used by both SOAP WSDL
• It should move out of SOAP
• More research is needed (scenarios)