Web Service

1

• Web Service
• Metadata Exchange
• (http//msdn.microsoft.com/ws/2004/02/mex)
• David Aiken
• (7/4/04)

2
Introduction

• This specification defines messages to retrieve
  specific types of metadata associated with an
  endpoint.
• Uses XML, SOAP(1.1, 1.2) and WSDL(1.1)
  extensibility models.
• Web services specifications (WS-) are designed
  to be composed with each other to provide a rich
  set of tools to provide security in the Web
  services environment.
• This specification specifically relies on other
  Web services specifications to provide secure,
  reliable, and/or transacted message delivery and
  to express Web service and client policy.

3
Web Services

• Web services use metadata to describe what other
  endpoints need to know to interact with them.
• - WS-Policy describes the capabilities,
  requirements and general characteristics of Web
  services.
• - WSDL(1.1) describes abstract message
  operations, concrete network protocols, and
  endpoint addresses used by Web services.
• - XML Schema(part1, part2) describes the
  structure and contents of XML-based messages
  received and sent by Web services.
• To bootstrap communication with a Web service,
  this specification defines three request/response
  message pairs to retrieve these three types of
  metadata
• 1) WS-Policy receiving endpoint or
  target namespace.
• 2) WSDL receiving endpoint or target
  namespace.
• 3) XML Schema with a given target
  namespace.
• Examples.

4
Terminology

• Key words(S. Bradners paper RFC 2119)
• MUST absolute requirement of the
  specification.
• SHOULD there may exist valid reasons in
  particular circumstances to ignore a particular
  item.
• MAY an item is truly optional.
• Anything in Italics indicate data types not
  values.
• ? 0 or 1.
• 0 or more.
• 1 or more.
• items inside are to be treated as groups wrt
  cardinality or choice.
• a point of extensibility allowing more
  attributes.
• Prefix
  XML Namespace Specification(s)
• Prefix XML namespace
  
  Specifications
• s (Either SOAP 1.1 or 1.2)
  
  (Either SOAP 1.1 or 1.2)
• s11 http//schemas.xmlsoap.org/soap/
  envelope
  SOAP 1.1 SOAP 1.1
• S12 http//www.w3.org/2003/05/soap-e
  nvelope
  SOAP 1.2 SOAP 1.2
• wsa http//schemas.xmlsoap.org/ws/20
  04/03/addressing WS-Addressing
  WSAddressing
• wsdl http//schemas.xmlsoap.org/wsdl/
  
  WSDL WSDL 1.1
• wsse http//schemas.xmlsoap.org/ws/200
  2/12/secext WS-SecurityPolicy
  WSSecurityPolicy
• wsp http//schemas.xmlsoap.org/ws/200
  2/12/policy
  WS-Policy WS-Policy

5
Example 1 Get Policy Request

• (01) lts12Envelope
• (02) xmlnss12'http//www.w3.org/2003
  /05/soap-envelope'
• (03) xmlnswsa'http//schemas.xmlsoap
  .org/ws/2004/03/addressing'
• (04) xmlnswsx'http//schemas.xmlsoap
  .org/ws/2004/03/mex' gt
• (05) lts12Headergt
• (06) ltwsaActiongt
• (07) http//schemas.xmlsoap.or
  g/ws/2004/03/mex/GetPolicy/Request
• (08) lt/wsaActiongt
• (09) ltwsaMessageIDgt
• (10) uuid73d7edfc-5c3c-49b9-
  ba46-2480caee43e9
• (11) lt/wsaMessageIDgt
• (12) ltwsaReplyTogt
• (13) ltwsaAddressgthttp//www.exa
  mple.com/MyEndpointlt/wsaAddressgt
• (14) lt/wsaReplyTogt
• (15) ltwsaTogt http//www.example.org/Y
  ourEndpointlt/wsaTogt
• (16) ltexMyRefProp xmlnsex'http//ww
  w.example.com/refs' gt
• (17) 78f2dc229597b529b81c4be
  f76453c96
• (18) lt/exMyRefPropgt
• (19) lt/s12Headergt

6
Example 1 Get Policy Request

• Lines(6-8) indicate that this is a Get Policy
  request
• Lines(10) is the MessageID for this request.
• Lines(15-18) illustrate a typical pattern where
  the endpoint is identified by a wsaTo header
  block (15) as well as an application-specific
  header block(16-18)
• Line(21) could alternatively include a target
  namespace instead of the associated receiving
  endpoint.
• Now to respond to the Get Policy Request

7
Example 2Get Policy Response

• (01) lts12Envelope
• (02) xmlnss12'http//www.w3.org/2003/0
  5/soap-envelope'
• (03) xmlnswsa'http//schemas.xmlsoap.o
  rg/ws/2004/03/addressing'
• (04) xmlnswsp'http//schemas.xmlsoap.o
  rg/ws/2002/12/policy'
• (05) xmlnswsx'http//schemas.xmlsoap.o
  rg/ws/2004/03/mex' gt
• (06) lts12Headergt
• (07) ltwsaActiongt
• (08) http//schemas.xmlsoap.o
  rg/ws/2004/03/mex/GetPolicy/Response
• (09) lt/wsaActiongt
• (10) ltwsaRelatesTogt
• (11) uuid73d7edfc-5c3c-49b9-
  ba46-2480caee43e9
• (12) lt/wsaRelatesTogt
• (13) ltwsaTogthttp//www.example.com/My
  Endpointlt/wsaTogt
• (14) lt/s12Headergt
• (15) lts12Bodygt
• (16) ltwsxGetPolicyResponsegt
• (17) ltwspPolicy
• (18) xmlnswsse'http//schemas.xm
  lsoap.org/ws/2002/12/secext' gt
• (19) ltwspOneOrMoregt

8
Example 2Get Policy Response

• Lines(7-9) says this message is a response to a
  Get Policy Request.
• Lines(10-12) this response is to the specific
  request (MessageID) we have just sent.
• Lines(17-29) contains the Policy corresponding
  to the receiver.

9
Retrieving Metadata

• Retrieving Policy
• A requestor MAY send a Get Policy Request message
  to an endpoint.
• If an endpoint accepts a Get Policy Request, it
  MUST reply with a Get Policy Response.
• Retrieving WSDL
• A requestor MAY send a Get WSDL Request message
  to an endpoint.
• If an endpoint accepts a Get WSDL Request, it
  MUST reply with a Get WSDL Response.
• Retrieving Schema
• A requestor MAY send a Get Schema Request message
  to an endpoint.
• If an endpoint accepts a Get Schema Request, it
  MUST reply with a Get Schema Response.

10
General outlineGet WSDL Request (1)

• ltsEnvelope ...gt
• ltsHeader ...gt
• ltwsaActiongt
• http//schemas.xmlsoap.org/ws
  /2004/03/mex/GetWSDL/Request
• lt/wsaActiongt
• ltwsaMessageIDgtxsanyURIlt/wsaMessage
  IDgt ?
• ltwsaReplyTogtendpoint-referencelt/wsa
  ReplyTogt ?
• ltwsaTogtxsanyURIlt/wsaTogt
• ...
• lt/sHeadergt
• ltsBody ...gt
• ltwsxGetWSDL ...gt
• ltwsxTargetNamespacegtxsanyURIlt/wsxTa
  rgetNamespacegt ?
• lt/wsxGetWSDLgt
• lt/sBodygt
• lt/sEnvelopegt
• Action MUST be included to define the metadata
  to be returned.
• ReplyTo if included MUST be of type
  wsaEndpointreferenceType.

0 or more
11
General outlineGet WSDL Response (2)

• ltsEnvelope ...gt
• ltsHeader ...gt
• ltwsaActiongt
• http//schemas.xmlsoap.org/ws/2
  004/03/mex/GetWSDL/Response
• lt/wsaActiongt
• ltwsaRelatesTogtxsanyURIlt/wsaRelatesTogt
  ?
• ltwsaTogtxsanyURIlt/wsaTogt
• ...
• lt/sHeadergt
• ltsBody ...gt
• ltwsxGetWSDLResponsegt
• ltwsdldefinitions ...gt ...
  lt/wsdldefinitionsgt
• lt/wsxGetWSDLResponsegt
• lt/sBodygt
• lt/sEnvelopegt
• Action MUST be included in the response message.
• RelatesTo header block MUST be included and MUST
  have that value (MAY include a MessageID).
• definitions SHOULD be repeated if there is gt 1
  WSDL in the target namespace

extensibility
1 or more
12
Faults (1)

• No WSDL
• If the receiver does not have a WSDL for the
  specified target namespace, the request MUST fail
  and the receiver MAY generate a SOAP fault as
  follows
• SOAP 1.1
• -faultcode s11client
• -faultstring e.g., unknown target namespace
• SOAP 1.2
• -s12 Code/s12value s12Sender
• -s12Code/s12Subcode/s12Value
  wsxUnkownTargetNamespace
• -s12Reason/s12Text e.g., unknown target
  namespace

13
Faults (2)

• Exposure
• If the receiver does not expose WSDL for itself,
  the request MUST fail, and the receiver MAY
  generate a SOAP fault as follows
• SOAP 1.1
• -faultcode s11client
• -faultstring e.g., WSDL unavailable for
  endpoint
• SOAP 1.2
• -s12 Code/s12value s12Sender
• -s12Code/s12Subcode/s12Value
  wsxWSDLUnavailable
• -s12Reason/s12Text e.g., WSDL unavailable
  for endpoint

14
General outline forGet Policy Request/Response

• have already have seen a working example for
  this.
• The faults would simply reply
• -If receiver does not have Policy for the
  specified target namespace,
• SOAP 1.1
• -faultstring e.g., unknown target namespace
• SOAP 1.2
• -s12Code/s12Subcode/s12Value
  wsxUnkownTargetNamespace
• -s12Reason/s12Text e.g., unknown target
  namespace
• -If receiver does not expose policy for itself,
• SOAP 1.1
• -faultstring e.g., policy unavailable for
  endpoint
• SOAP 1.2
• -s12Code/s12Subcode/s12Value
  wsxUnkownTargetNamespace
• -s12Reason/s12Text e.g., unknown target
  namespace

15
General outlineGet Schema Request (1)

• ltsEnvelope ...gt
• ltsHeader ...gt
• ltwsaActiongt
• http//schemas.xmlsoap.org/ws
  /2004/03/mex/GetSchema/Request
• lt/wsaActiongt
• ltwsaMessageIDgtxsanyURIlt/wsaMessage
  IDgt ?
• ltwsaReplyTogtendpoint-referencelt/wsa
  ReplyTogt ?
• ltwsaTogtxsanyURIlt/wsaTogt
• ...
• lt/sHeadergt
• ltsBody ...gt
• ltwsxGetSchema ...gt
• ltwsxTargetNamespacegtxsanyURIlt/wsxTa
  rgetNamespacegt ?
• lt/wsxGetSchemagt
• lt/sBodygt
• lt/sEnvelopegt
• Action MUST be included to define the metadata
  to be returned.
• ReplyTo if included MUST be of type
  wsaEndpointreferenceType.

16
General outlineGet Schema Response (2)

• ltsEnvelope ...gt
• ltsHeader ...gt
• ltwsaActiongt
• http//schemas.xmlsoap.org/ws/2
  004/03/mex/GetSchema/Response
• lt/wsaActiongt
• ltwsaRelatesTogtxsanyURIlt/wsaRelatesTogt
  ?
• ltwsaTogtxsanyURIlt/wsaTogt
• ...
• lt/sHeadergt
• ltsBody ...gt
• ltwsxGetSchemaResponsegt
• ltxsschemagt ... lt/xsschemagt
• lt/wsxGetSchemaResponsegt
• lt/sBodygt
• lt/sEnvelopegt
• Action MUST be included in the response message.
• RelatesTo header block MUST be included and MUST
  have that value (MAY include a MessageID).
• schema SHOULD be repeated if there is gt 1 XML
  Schema in the target namespace.

17
Fault

• No Schema
• If the receiver does not have a schema for the
  specified target namespace, the request MUST fail
  and the receiver MAY generate a SOAP fault as
  follows
• SOAP 1.1
• -faultcode s11client
• -faultstring e.g., unknown target namespace
• SOAP 1.2
• -s12 Code/s12value s12Sender
• -s12Code/s12Subcode/s12Value
  wsxUnkownTargetNamespace
• -s12Reason/s12Text e.g., unknown target
  namespace
• Unsure as to why there is no documentation on a
  receiver that does not expose its Schema!?

18
Other Faults (1)

• If a get Policy, Get WSDL or Get Schema does not
  comply with the outlines we have just covered,
  the request MUST fail, and the receiver MAY
  generate a SOAP faults as follows
• SOAP 1.1
• -faultcode s11client
• -faultstring e.g., message is invalid
• SOAP 1.2
• -s12 Code/s12value s12Sender
• -s12Code/s12Subcode/s12Value
  wsxInvalidRequest
• -s12Reason/s12Text e.g., message is invalid

19
Other Faults (2)

• If the amount of data to be sent in a get Policy,
  Get WSDL or Get Schema response exceeds what the
  receiver can include, the request MUST fail, and
  the receiver MAY generate a SOAP faults as
  follows
• SOAP 1.1
• -faultcode s11client
• -faultstring e.g., response is too large
• SOAP 1.2
• -s12 Code/s12value s12Receiver
• -s12Code/s12Subcode/s12Value
  wsxResponseTooLarge
• -s12Reason/s12Text e.g., response is too
  large

20
Normative Protocol Binding

• A binding for the messages, SOAP(1.1) over http
  as constrained by the Basic Profile(1.0) is
  recommended as a means to bootstrap
  communication.
• A web service if free to support these messages
  over other bindings in addition to , or in place
  of, the WSDL(1.1) binding.
• If no other binding is explicitly stated then the
  default binding is assumed to be SOAP over http.

21
Conclusions

• We saw a working example of a Get Policy
  Request/Response.
• Also general outlines of Get WSDL and Get Schema
  including their faults
• It is strongly recommended that the communication
  between web Services be secured using the
  mechanisms described in WS-Security.(presentation
  ?)