Tiziana'Ferraricnaf'infn'it

1
WS-Addressing

• Tiziana.Ferrari_at_cnaf.infn.it
• INFN CNAF
• Corso di Laurea specialistica in Informatica
• Anno Acc. 2004/2005

2
Outline

• PART I Uniform Resource Identifier and
  WS-Addressing
• PART II WS-Addressing Endpoint References
• PART III WS-Addressing Message Header
  Information
• References

3
Uniform Resource Identifier

• A Uniform Resource Identifier (URI) is a compact
  string of characters for identifying an abstract
  or physical resource.
• Uniform Uniformity provides several benefits
• it allows different types of resource identifiers
  to be used in the same context, even when the
  mechanisms used to access those resources may
  differ
• uniform semantic interpretation of common
  syntactic conventions across different types of
  resource identifiers
• introduction of new types of resource identifiers
  without interfering with the way that existing
  identifiers are used
• Identifiers can be reused in many different
  contexts, thus permitting new applications or
  protocols to leverage a pre-existing, large, and
  widely-used set of resource identifiers.
• Resource A resource can be anything that has
  identity (e.g., an electronic document, an image,
  a service, and a collection of other resources.
  Not all resources are network"retrievable" e.g.,
  human beings, corporations, and bound books in a
  library can also be considered resources.
• Identity The resource is the conceptual mapping
  to an entity or set of entities, not necessarily
  the entity which corresponds to the mapping at
  any particular instance in time. Thus, a
  resource can remain constant even when its
  content---the entities to which it currently
  corresponds---changes over time.
• Identifier an object that can act as a reference
  to something that has identity. In the case of
  URI, the object is a sequence of characters with
  a restricted syntax.

4
URI, URL, URN

• A URI can be further classified as a locator, a
  name, or both
• Uniform Resource Locator (URL) refers to the
  subset of URI that identify resources via a
  representation of their primary access mechanism
  (e.g., their network "location"), rather than
  identifying the resource by name or by some other
  attribute(s) of that resource.
• Although many URL schemes are named after
  protocols, this does not imply that the only way
  to access the URL's resource is via the named
  protocol. Gateways, proxies, caches, and name
  resolution services might be used to access some
  resources, independent of the protocol of their
  origin, and the resolution of some URL may
  require the use of more than one protocol (e.g.,
  both DNS and HTTP are typically used to access an
  "http" URL's resource when it can't be found in a
  local cache).
• Uniform Resource Name (URN) refers to the subset
  of URI that are required to remain globally
  unique and persistent even whe the resource
  ceases to exist or becomes unavailable.

5
URI Examples

• The following examples illustrate URI that are in
  common use

6
Absolute vs Relative Identifiers

• An absolute identifier refers to a resource
  independent of thecontext in which the identifier
  is used.
• A relative identifier refers to a resource by
  describing the difference within a hierarchical
  namespace between the current context and an
  absolute identifier of the resource.
• Some URI schemes support a hierarchical naming
  system, where the hierarchy of the name is
  denoted by a "/" delimiter separating the
  components in the scheme.
• Example ltA href"../x"gta hypertext anchorlt/Agt

7
URI Syntax

• Absolute URIs are written as follows
• ltschemegtltscheme-specific-partgt
• An absolute URI contains
• the name of the scheme being used (ltschemegt)
  followed by a colon ("") and
• a string (the ltscheme-specific-partgt) whose
  interpretation depends on the scheme.
• The URI syntax does not require that the
  scheme-specific-part have any general structure
  or set of semantics which is common among all
  URI.
• A subset of URI do share a common syntax for
  representing hierarchical relationships within
  the namespace. This "generic URI" syntax
  consists of a sequence of four main components,
  each of which, except ltschemegt, may be absent
  from a particular URI
• ltschemegt//ltauthoritygtltpathgt?ltquerygt
• For example, some URI schemes do not allow
  an ltauthoritygt component, and others do not use a
  ltquerygt component.
• absoluteURI scheme "" ( hier_part
  opaque_part )
• Relative URIs the syntax for relative URI is a
  shortened form of that for absolute URI, where
  some prefix of the URI is missing and certain
  path components ("." and "..") have a special
  meaning when, and only when, interpreting a
  relative path.

8
WS-Addressing

• Using today's approach, the source and
  destination information are not part of the
  message itself. This can cause several problems.
  The information can be lost if a transport
  connection terminates (for example, if the
  response takes a long time and the connection
  times out) or if the message is forwarded by an
  intermediary such as a firewall.
• WS-Addressing provides a mechanism to place the
  target, source and other important address
  information directly within the Web service
  message. In short, WS-Addressing decouples
  address information from any specific transport
  model.
• In many scenarios messages are targeted directly
  to a service and the addressing information in
  the message can be described simply using a URL.
  But in practice, we often find that messages are
  targeted to specific elements or resources within
  a service. For example, a coordination service
  might be coordinating many different tasks. The
  coordinator needs to associate most incoming
  messages with a specific task instance that it
  manages and not the coordination service itself. 
  
• WS-Addressing provides a simple yet powerful
  mechanism called an endpoint reference for
  addressing entities managed by a service. While
  such information could be encoded in an ad-hoc
  manner within the URL of the service, the
  endpoint references provides a standard XML
  element that enables a structured approach to
  encoding this fine-grained addressing.

9
WS-Addressing (cont)

• WS-Addressing provides transport and
  application-neutral mechanisms to address Web
  services and messages.
• It enables messaging systems to support message
  transmission through networks that include
  processing nodes such as endpoint managers,
  firewalls, and gateways in a transport-neutral
  manner.
• Web Services Addressing (WS-Addressing) defines
  two interoperable constructs that convey
  information that is typically provided by
  transport protocols and messaging systems
  endpoint references and message information
  headers.
• Endpoint references convey the information needed
  
• to identify a Web service endpoint to provide
  addresses for individual messages sent to and
  from Web services
• Message information headers
• to convey end-to-end message characteristics
  including
• addressing for source and destination endpoints
• Message identity

10
PART IIWS-Addressing Endpoint Reference
11
Endpoint reference and message information headers

• Web service endpoint a (referenceable) entity,
  processor, or resource where Web service messages
  can be targeted. Endpoint references convey the
  information needed to identify/reference a Web
  service endpoint, and may be used in several
  different ways
• used to provide addresses for individual messages
  sent to and from Web services
• to convey the information needed to access a Web
  service endpoint.
• To deal with this last usage case this
  specification defines a family of message
  information headers that allows uniform
  addressing of messages independent of underlying
  transport. These message information headers
  convey end-to-end message characteristics
  including addressing for source and destination
  endpoints as well as message identity.

12
Endpoint XML Representation

• ltwsaEndpointReferencegt
• ltwsaAddressgtxsanyURIlt/wsaAddressgt
• ltwsaReferencePropertiesgt... lt/wsaReferenceProper
  tiesgt ?
• ltwsaReferenceParametersgt... lt/wsaReferenceParame
  tersgt ?
• ltwsaPortTypegtxsQNamelt/wsaPortTypegt ?
• ltwsaServiceName PortName"xsNCName"?gtxsQNamelt/w
  saServiceNamegt?
• ltwspPolicygt ... lt/wspPolicygt
• lt/wsaEndpointReferencegt
• Example
• ltwsaEndpointReference xmlnswsa"..."
  xmlnsfabrikam"..."gt ltwsaAddressgthttp//www.fabr
  ikam123.example/acctlt/wsaAddressgt
  ltwsaPortTypegtfabrikamInventoryPortTypelt/wsaPort
  Typegt
• lt/wsaEndpointReferencegt

13
Endpoint reference components

• address URI (mandatory) An address URI that
  identifies the endpoint. This may be a network
  address or a logical address.
• reference properties xsany (0..unbounded). A
  reference may contain a number of individual
  properties that are required to identify the
  entity or resource being conveyed. Reference
  identification properties are element information
  items that are named by QName and are required to
  properly dispatch messages to endpoints at the
  endpoint side of the interaction. Reference
  properties are provided by the issuer of the
  endpoint reference and are otherwise assumed to
  be opaque to consuming applications.
• reference parameters xsany (0..unbounded).
  Individual parameters are associated with the
  endpoint to facilitate a particular interaction.
  Reference parameters are element information
  items that are named by QName and are required to
  properly interact with the endpoint. Reference
  parameters are also provided by the issuer of the
  endpoint reference and are otherwise assumed to
  be opaque to consuming applications.
• selected port type QName (0..1) The QName of
  the primary portType of the endpoint being
  conveyed.
• service-port (QName, NCName (0..1)) (0..1)
  the QName identifying the WSDL service element
  that contains the definition of the endpoint
  being conveyed. The service name provides a link
  to a full description of the service endpoint. An
  optional non-qualified name identifies the
  specific port in the service that corresponds to
  the endpoint.
• policy wsppolicy (0..unbounded) A variable
  number of XML policy elements as described in
  WS-Policy describing the behavior, requirements
  and capabilities of the endpoint. Policies may be
  included in an endpoint to facilitate easier
  processing by the consuming application, or
  because the policy was dynamically generated.
  However, embedded policies are not authoritative
  and may be stale or incoherent with the policies
  associated with the endpoint at the time when the
  interaction occurs.

14
Binding Endpoint Reference

• Information contained in the endpoint reference
  is mapped to the message and protocol fields
  according to a transformation that is dependent
  on the protocol and data representation used to
  send the message.
• The specification defines the SOAP binding for
  endpoint references. There are two rules
• The address property in the endpoint reference
  is copied in the destination header field of
  the SOAP message.
• Each reference property and reference
  parameter element becomes a header block in the
  SOAP message. The element information item of
  each reference property or reference
  parameter (including all of its children,
  attributes and in-scope namespaces) is to be
  added as a header block in the new message.

15
Binding Endpoint Reference Example

• ltwsaEndpointReference xmlnswsa"..."
  xmlnsfabrikam"..."gt ltwsaAddressgthttp//www.fabr
  ikam123.example/acct
• lt/wsaAddressgt
• ltwsaReferencePropertiesgt ltfabrikamCustomerKeygt
  123456789lt/fabrikamCustomerKeygt
  lt/wsaReferencePropertiesgt
• ltwsaReferenceParametersgt ltfabrikamShoppingCart
  gtABCDEFGlt/fabrikamShoppingCartgt
  lt/wsaReferenceParametersgt lt/wsaEndpointReference
  gt
• Binding
• ltSEnvelope xmlnsS"http//www.w3.org/2003/05/soa
  p-envelope"
• xmlnswsa""http//schemas.xmlsoap.org/ws/2004/0
  8/addressing"
• xmlnsfabrikam"... "gt
• ltSHeadergt
• ...
• ltwsaTogthttp//www.fabrikam123.example/acctlt/wsa
  Togt ltfabrikamCustomerKeygt123456789lt/fabrikamCu
  stomerKeygt ltfabrikamShoppingCartgtABCDEFGlt/fabrik
  amShoppingCartgt
• ...
• lt/SHeadergt
• ltSBodygt
• ...
• lt/SBodygt
• lt/SEnvelopegt

()
() during binding, the wsaAddress is copied
into the SOAP destination address, i.e.
wsaTo Note wsa in the SOAP message is related
to a soap- specific namespace.
16
Endpoint Reference Comparison

• The relation between the behaviors of the
  endpoints represented by two endpoint references
  with the same address and the same reference
  properties.
• The two endpoints accept the same sets of
  messages.
• They follow and require the same set of policies.
  That is, the XML Schema, WSDL, and WS-Policy
  metadata applicable to the two references are the
  same. In particular, the policies applicable to
  the two endpoints are the same regardless of the
  values of the embedded policy. Embedded
  policies are not authoritative and may be stale
  or incoherent with the policies associated with
  the endpoint.
• The address properties of two endpoint
  references are compared according to Section 6 of
  RFC 2396. The reference properties of two
  endpoint references are equal if
• they contain the same number of individual
  properties
• for each reference property in one endpoint
  reference there exists an equivalent reference
  property in the other.

17
PART III WS-Addressing Message Information Header
18
Message Information Headers

• The message information headers collectively
  augment a message with a set of abstract
  properties. These properties enable the 1.
  identification and 2. location of the endpoints
  involved in an interaction (one-way,
  request/response).
• destination URI (mandatory) The address of
  the intended receiver of this message.
• source endpoint endpoint reference (0..1)
  endpoint where the message originated from.
• reply endpoint endpoint reference (0..1)
  identifies the intended receiver for replies to
  this message. If a reply is expected, a message
  MUST contain a reply endpoint. If the reply
  endpoint is absent, the contents of the source
  endpoint may be used to formulate a message to
  the source. This property MAY be absent if the
  message has no meaningful reply. If this property
  is present, the message id property is
  REQUIRED.
• fault endpoint endpoint reference (0..1)
  identifies the intended receiver for faults
  related to this message. If the fault endpoint
  is absent, the sender MAY use the contents of the
  reply endpoint to formulate the fault message.
  If both the fault endpoint and reply endpoint
  are absent, the sender MAY use the contents of
  the source endpoint to formulate the fault
  message. If this property is present, the
  message id property is REQUIRED.

19
Message Information Headers (cont)

• action URI (mandatory) An identifier that
  uniquely (and opaquely) identifies the semantics
  implied by this message. It is RECOMMENDED that
  value of the action property is a URI
  identifying an input, output, or fault message
  within a WSDL port type. An action may be
  explicitly or implicitly associated with the
  corresponding WSDL definition. Finally, if in
  addition to the action property, a SOAP Action
  URI is encoded in a request, the URI of the SOAP
  Action MUST be the same as the one specified by
  the action property.
• message id URI (0..1) A URI that uniquely
  identifies this message in time and space. Two
  messages with a distinct application intent
  cannot share a message id property. A message
  MAY be retransmitted for any purpose including
  communications failure and MAY use the same
  message id property. The value of this property
  is an opaque URI whose interpretation beyond
  equivalence is not defined in this specification.
  If a reply is expected, this property MUST be
  present.
• relationship (QName, URI) (0..unbounded) A
  pair of values that indicate how this message
  relates to another message. The type of the
  relationship is identified by a QName. The
  related message is identified by a URI that
  corresponds to the related message's message id
  property.
• E.g. wsaReply ? indicates that this is a
  reply to the message identified by the URI

20
Message Information Headers

• The information in these headers is immutable and
  not intended to be modified along the message
  path.
• The following describes the contents of the
  message information header blocks
• ltwsaMessageIDgt xsanyURI lt/wsaMessageIDgt
• ltwsaRelatesToRelationshipType"..."?gtxsanyURIlt/
  wsaRelatesTogt
• ltwsaTogtxsanyURIlt/wsaTogt ltwsaActiongtxsanyURIlt
  /wsaActiongt
• ltwsaFromgtendpoint-referencelt/wsaFromgt
• ltwsaReplyTogtendpoint-referencelt/wsaReplyTogt
• ltwsaFaultTogtendpoint-referencelt/wsaFaultTogt

21
Request Message Using Message Information Header
Block
ltwsaMessageIDgt xsanyURI lt/wsaMessageIDgt
ltwsaRelatesToRelationshipType"..."?gtxsanyURIlt/
wsaRelatesTogt ltwsaTogtxsanyURIlt/wsaTogt
ltwsaActiongtxsanyURIlt/wsaActiongt
ltwsaFromgtendpoint-referencelt/wsaFromgt
ltwsaReplyTogtendpoint-referencelt/wsaReplyTogt ltws
aFaultTogtendpoint-referencelt/wsaFaultTogt
SOAP 1.2 Request message
ltSEnvelope xmlnsS"http//www.w3.org/2003/0
5/soap-envelope" xmlnswsa"http//schemas.xml
soap.org/ws/2004/08/addressing"
xmlnsf123"http//www.fabrikam123.example/svc53"gt
ltSHeadergt ltwsaMessageIDgtuuidaaaabbbb-c
ccc-dddd-eeee-ffffffffffff lt/wsaMessageIDgt
ltwsaReplyTogt ltwsaAddressgthttp//business456
.example/client1lt/wsaAddressgt lt/wsaReplyTogt
ltwsaTo SmustUnderstand"1"gtmailtojoe_at_fabrikam
123.examplelt/wsaTogt ltwsaActiongthttp//fabrikam
123.example/mail/Deletelt/wsaActiongt
lt/SHeadergt ltSBodygt ltf123Deletegt
ltmaxCountgt42lt/maxCountgt lt/f123Deletegt
lt/SBodygt lt/SEnvelopegt
22
Reply Message Using Message Information Header
Block
ltSEnvelope xmlnsS"http//www.w3.org/2003/0
5/soap-envelope" xmlnswsa"http//schemas.xml
soap.org/ws/2004/08/addressing"
xmlnsf123"http//www.fabrikam123.example/svc53"gt
ltSHeadergt ltwsaMessageIDgtuuidaaaabbbb-c
ccc-dddd-eeee-ffffffffffff lt/wsaMessageIDgt
ltwsaReplyTogt ltwsaAddressgthttp//business456
.example/client1lt/wsaAddressgt lt/wsaReplyTogt
ltwsaTo SmustUnderstand"1"gtmailtojoe_at_fabrikam
123.examplelt/wsaTogt ltwsaActiongthttp//fabrikam
123.example/mail/Deletelt/wsaActiongt
lt/SHeadergt ltSBodygt ltf123Deletegt
ltmaxCountgt42lt/maxCountgt lt/f123Deletegt
lt/SBodygt lt/SEnvelopegt
SOAP 1.2 Request Message
Different
ltSEnvelope xmlnsS"http//www.w3.org/2003/0
5/soap-envelope" xmlnswsa"http//schemas.xml
soap.org/ws/2004/08/addressing"
xmlnsf123"http//www.fabrikam123.example/svc53"gt
ltSHeadergt ltwsaMessageIDgt
uuidaaaabbbb-cccc-dddd-eeee-wwwwwwwwwwwlt/wsaMess
ageIDgt ltwsaRelatesTogt uuidaaaabbbb-cccc-d
ddd-eeee-fffffffffffflt/wsaRelatesTogt
ltwsaTo SmustUnderstand"1"gthttp//business456.ex
ample/client1lt/wsaTogt ltwsaActiongthttp//fa
brikam123.example/mail/DeleteAcklt/wsaActiongt
lt/SHeadergt ltSBodygt ltf123DeleteAck/gt
lt/SBodygt lt/SEnvelopegt
Identical
SOAP 1.2 Reply Message
Identical
23
wsaAction (Explicit association with WSDL
operations)

• The action element, which is included in the SOAP
  header, can be explicitly associated to a message
  in a WSDL document, through the wsaAction
  attribute. Example (WSDL excerpt)

ltdefinitions targetNamespace"http//example.com/s
tockquote" ...gt ... ltportType
name"StockQuotePortType"gt ltoperation
name"GetLastTradePrice"gt ltinput
message"tnsGetTradePricesInput"
wsaAction"http//example.com/GetQuote"/gt
ltoutput message"tnsGetTradePricesOutput"
wsaAction"http//example.com/Quote"/gt
lt/operationgt lt/portTypegt ...
lt/definitionsgt
24
References

• Web Services Addressing (WS-Addressing),
  A.Bosworth, D.Box, E.Christensen, et alt. March
  2004.
• Uniform Resource Identifiers (URI) Generic
  Syntax RFC 2396, August 1998.