CS556: Distributed Systems

1
CS-556 Distributed Systems
SOAP Web Services

• Manolis Marazakis
• maraz_at_csd.uoc.gr

2
Evolution of integration methods
Web App. Standards (Web Services)
2001
Web Protocol Standards (HTTP, HTML, XML,
RosettaNet, OBI, cXML, )
Late 1990s
Early 1990s
App. Integration Standards
-1990
Custom static integration
3
Web Services

• Machine-to-machine communication
• Description of service semantics metadata
• WSDL Web Service Definition Language
• Discovery of appropriate services
• UDDI Universal Description, Discovery
  Integration service
• Allow services to be defined, deployed,
  manipulated evolved in an automated fashion
• Basis for expressing higher-level business logic
• Using flow languages
• Potential
• EDI replacement
• ERP accelerator
• Reduce middleware proliferation
• Improve desktop integration

4
Drivers for Web Services

• Microsoft
• .NET, Hailstorm
• Sun
• Sun ONE
• HP
• e-speak
• IBM
• Dynamic e-business
• UN/CEFACT OASIS
• ebXML
• Plus Oracle, Borland,

Submitted to IETF - Nov. 1999 W3C WG -
September 2000
5
RPC Interoperability problems

• Naming of communication endpoints
• CORBA IORs
• DCOM OBJREFs
• Support for multiple interfaces per object
• CORBA implicitly, there is 1 interface in an IOR
• DCOM multiple interfaces Iuknown
• Format of parameter values
• CORBA CDR
• DCOM Network Data Representation

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IIOP vs DCOM (I)
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IIOP vs DCOM (II)
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URIs, URLs, URNs

• Universal Resource Identifier
• A formatted string that uniquely identifies a
  resource
• Uniform Resource Locator
• encode the underlying protocol needed to locate
  the resource, as well as its location
• http//" lthostgt "" ltportgt ltpathgt "?" ltqrygt
• Uniform Resource Name
• location-independent in no way imply any
  protocol or mechanism for locating the resource
  being identified
• "urn" ltNIDgt "" ltNSSgt
• ltNIDgt namespace
• ltNSSgt namespace-specific string
• urnuuid00000000-0000-0000-C000-000000000046

9
Simple Object Access Protocol

• A light-weight XML messaging convention
• exchange of structured typed information
• no application or transport semantics
• XML datagrams -gt extensibility
• Common use RPC-over-HTTP (using XML)
• getStockQuote(), issueQuery(), sendOrder()
• Other uses are possible
• One-way messaging
• Multicast
• The KISS principle
• absolute minimum of functionality

Keep It Simple, Stupid!
10
SOAP reference
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UDDI (I)

• Universal Description, Discovery Integration
• An industry initiative for B2B interoperability
• First specs outlined by Ariba, Microsoft IBM
• Ariba, Microsoft, IBM, HP, SAP operator nodes
• Business Registry of Web services
• Allow companies to register their business
  services
• Accessible via SOAP
• and via browser
• lt businessEntity, businessService,
  bindingTemplate, tModel gt
• Web service
• a self-describing, self-contained, modular unit
  of application logic
• provides some business functionality to other
  apps
• Web services can be mixed matched with other
  web services to execute a larger workflow or
  business Tx.
• WSDL Web Service Definition Language

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UDDI (II)

• XML Schema for UDDI
• ltbusinessEntitygt Business information
• ltbusinessServicegt Service information
• ltbindingTemplategt Binding information
• lttModelgt Information on specifications
• technical fingerprint list of references
• Inquiry API
• Publisher API
• Coping with Failures ?
• inability to predict, detect, or recover from
  failures within the systems of the remote partner
• Use cached ltbindingTemplategt, retry-on-failure
• Rely on partner to update registry entry

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UDDI (III)
Discrete business roles
The business of e-business services (IBM)

• Lifecycle
• Build
• Deploy
• Run
• Manage

• Publish
• WSDL
• Find
• UDDI
• Bind
• SOAP

Applications will increasingly be based on
compositions of services discovered marshaled
dynamically at runtime.
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UDDI Sample Interaction (I)
lt?xml version'1.0' encoding'UTF-8'?gt
ltEnvelope xmlns'http//schemas.xmlsoap.org/soap/e
nvelope/'gt ltBodygt ltfind_business
generic"1.0" xmlns"urnuddi-orgapi"gt
ltnamegtMicrosoftlt/namegt lt/find_businessgt
lt/Bodygt lt/Envelopegt
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UDDI Sample Interaction (II)
ltbusinessList generic"1.0" operator"Microsoft
Corporation" truncated"false"
xmlns"urnuddi-orgapi"gt ltbusinessInfosgt
ltbusinessInfo businessKey"0076B468-EB27-42E5-AC
09-9955CFF462A3"gt ltnamegtMicrosoft
Corporationlt/namegt ltdescription
xmllang"en"gtEmpowering people through great
software - any time, any place and on any
device lt/descriptiongt ltserviceInfosgt
ltserviceInfo businessKey"0076B468-EB27-42E5
-AC09-955CFF462A3"
serviceKey"8BF2F51F-8ED4-43FE-B665-38D8205D1333"gt
ltnamegtElectronic Business
Integration Serviceslt/namegt
lt/serviceInfogt
. ltserviceInfo
businessKey"0076B468-EB27-42E5-AC09-955CFF462A3"
serviceKey"D2BC296A-723B-4
C45-9ED4-494F9E53F1D1"gt ltnamegtUDDI
Web Serviceslt/namegt lt/serviceInfogt
.
lt/serviceInfosgt lt/businessInfogt
lt/businessInfosgt lt/businessListgt
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UDDI Sample Interaction (III)
ltfind_service generic'1.0' xmlns'urnuddi-orgap
i' businessKey'0076B468-EB27-42E5-AC09-9955
CFF462A3'gt ltnamegtUDDI Web Serviceslt/namegt
lt/find_servicegt
ltserviceList generic"1.0" operator"Microsoft
Corporation" truncated"false"
xmlns"urnuddi-orgapi"gt ltserviceInfosgt
ltserviceInfo businessKey"0076B468-EB27-42E5-AC09
-9955CFF462A3"
serviceKey"D2BC296A-723B-4C45-9ED4-494F9E53F1D1"gt
ltnamegtUDDI Web Serviceslt/namegt
lt/serviceInfogt lt/serviceInfosgt
lt/serviceListgt
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UDDI Sample Interaction (IV)
ltget_serviceDetail generic'1.0'
xmlns'urnuddi-orgapi'gt
ltserviceKeygtD2BC296A-723B-4C45-9ED4-494F9E53F1D1lt/
serviceKeygt lt/get_serviceDetailgt
ltserviceList generic"1.0" operator"Microsoft
Corporation" truncated"false"
xmlns"urnuddi-orgapi"gt ltserviceInfosgt
ltserviceInfo businessKey"0076B468-EB27-42E5-AC09
-9955CFF462A3"
serviceKey"D2BC296A-723B-4C45-9ED4-494F9E53F1D1"gt
ltnamegtUDDI Web Serviceslt/namegt
lt/serviceInfogt lt/serviceInfosgt
lt/serviceListgt
ltfind_business generic'1.0' xmlns'urnuddi-orga
pi'gt lttModelBaggtlttModelKeygtuuid4CD7E4BC-648B
-426D-9936-443EAAC8AE23lt/tModelKeygtlt/tModelBaggt
lt/find_businessgt
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UDDI Sample Interaction (V)
ltserviceDetail generic"1.0" operator"Microsoft
Corporation" truncated"false"
xmlns"urnuddi-orgapi"gt ltbusinessService
businessKey"0076B468-EB27-42E5-AC09-9955CFF462A3"
serviceKey"D2BC296A-723B-4C
45-9ED4-494F9E53F1D1"gt ltnamegtUDDI Web
Serviceslt/namegt ltdescription
xmllang"en"gtUDDI SOAP/XML message-based
programmatic web service interfaces.lt/descript
iongt ltbindingTemplatesgt ltbindingTemplate
bindingKey"A9CAFBE4-11C6-4BFE-90F5-595970D3DE24"
serviceKey"D2BC296A-723B-4C45-9ED4-494F
9E53F1D1"gt ltdescription
xmllang"en"gtProduction UDDI server, Inquiry
interface lt/descriptiongt
ltaccessPoint URLType"http"gthttp//uddi.microsoft.
com/inquirelt/accessPointgt
lttModelInstanceDetailsgt
lttModelInstanceInfo tModelKey"uuid4CD7E4BC-648B-
426D-9936 443EAAC8AE23"gt ltdescription
xmllang"en"gtUDDI SOAP Inquiry
Interfacelt/descriptiongt
lt/tModelInstanceInfogt
lt/tModelInstanceDetailsgt
lt/bindingTemplategt
.
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SOAP Mandatory Features

• Transport Binding
• how to get the message to its destination
• isolates message from transport, for portability
  across transports
• Message Envelope
• what features services are represented in a
  message
• as blocks
• who should deal with them
• actor attribute implied semantics
• whether they are optional or mandatory
• mustUnderstand attribute implied semantics

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SOAP Fault Codes
100 Version Mismatch
- The call was using an unsupported SOAP
version. 200 Must Understand
- An XML element was received that
contained an
element tagged with mustUnderstand"true"
that was not understood by
the receiver. 300 Invalid Request
- The receiving application did
not process the request
because it was incorrectly formed or not
supported by the
application. 400 Application
Faulted - The receiving
application faulted when processing the
request. The detail element
contains the application-
specific fault.
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SOAP Optional Features

• Serialisation Mechanism
• to exchange instances of application-defined data
  types and directed graphs
• uniform model for serializing abstract data
  models that cannot be expressed in XML Schema
• Section 5 encoding representation of
  programming language types
• RPC Convention
• how to make calls responses for a particular
  type of service

Open issue Security of XML documents ?
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SOAP Example
POST /Accounts/Henrik HTTP/1.1 Host
www.webservicebank.com Content-Length nnnn
Content-Type text/xml charset"utf-8"
SOAPAction "Some-URI" ltSOAPEnvelope
xmlnsSOAP"http//schemas.xmlsoap.org/soap/envelo
pe/" SOAPencodingStyle"http//schemas.xmlsoap
.org/soap/encoding/"gt ltSOAPHeadergt
lttTransaction xmlnst"some-URI"
SOAPmustUnderstand"1"gt lt/tTransactiongt
lt/SOAPHeadergt ltSOAPBodygt
ltmDeposit xmlnsm"Some-URI"gt
ltmamountgt200lt/mamountgt lt/mDepositgt
lt/SOAPBodygt lt/SOAPEnvelopegt
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Alternative SOAP Stacks

• Based on HTTP
• Based on SMTP
• Based on SIP (on top of UDP)

• Support for extension modules
• - encryption
• - digital signatures
• - explicit routing (SOAP-RP)
• - caching

• Modules can address any SOAP processor using the
  "actor" attribute
• Can be optional or mandatory using the
  "mustUnderstand" attribute

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SOAP Message Paths Routing

• SOAP is built on underlying transports, which
  have their own concepts of
• Message Exchange Pattern
• HTTP request/response
• SMTP one-way
• Message Routing
• HTTP proxies
• DNS lookup
• SMTP DNS MX record, intermediary configuration
  
• Some applications using SOAP may need to
  determine their own concepts of MEP routing
• Message path routing has an implied
  relationship with the processing model
• intra-node processing inter-node processing are
  linked.

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SOAP References

• SOAP 1.1 specification
• http//www.w3.org/TR/SOAP
• W3C XML Protocol Activity
• http//www.w3.org/2000/xp/
• SOAP/WebServices Resource Center
• http//www.soap-wrc.com/webservices/
• http//www.webservices.org/
• http//www.soaprpc.com/
• Public SOAP Services listing
• http//www.xmethods.com/
• http//msdn.microsoft.com/msdnmag/issues/0300/soap
  /print.asp