WSDL WSDL and UML

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WSDL WSDL and UML
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under contract IST-2003-508833
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UML to WSDL process
user
Client application
Servelet
Use case
interface
Class diagram
WSDL (interface Definition)
implementation
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Starting with UML

• Create a description of requirements in a use
  case diagram
• Create a description of interactions in a
  sequence diagram
• Create a description of the application (methods
  and attributes/variables) in a class diagram

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Barnes Noble price client use case diagram

• This is an extremely simple use case

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bnclient class diagram
This is the simplest web service client
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Mapping UML - WSDL

• Attributes/variables become types
• Methods become operations
• Classes become portType

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bnquote WSDL
lt?xml version"1.0"?gt ltdefinitions
name"BNQuoteService" targetNamespace"BNQuoteServ
ice.wsdl" xmlnsxsd"http//www.w3.org/2001/XMLSch
ema" xmlnssoap"http//schemas.xmlsoap.org/wsdl/s
oap/" xmlns"http//schemas.xmlsoap.org/wsdl/"
xmlnstns"BNQuoteService.wsdl" gt ltmessage
name"getPriceRequest"gt ltpart name"isbn"
type"xsdstring"/gt lt/messagegt ltmessage
name"getPriceResponse"gt ltpart name"return"
type"xsdfloat"/gt lt/messagegt ltportType
name"BNQuotePortType"gt ltoperation
name"getPrice"gt ltinput message"tnsgetPriceRe
quest" name"getPrice"/gt ltoutput
message"tnsgetPriceResponse" name"getPriceRespo
nse"/gt lt/operationgt lt/portTypegt
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WSDL continued
ltbinding name"BNQuoteBinding" type"tnsBNQuotePo
rtType"gt ltsoapbinding style"rpc"
transport"http//schemas.xmlsoap.org/soap/http"/gt
ltoperation name"getPrice"gt ltsoapoperation
soapAction""/gt ltinput name"getPrice"gt ltso
apbody use"encoded" namespace"urnxmethods-BNPr
iceCheck" encodingStyle"http//schemas.xmlsoa
p.org/soap/encoding/"/gt lt/inputgt ltoutput
name"getPriceResponse"gt ltsoapbody
use"encoded" namespace"urnxmethods-BNPriceCheck
" encodingStyle"http//schemas.xmlsoap.org/so
ap/encoding/"/gt lt/outputgt lt/operationgt lt/bin
dinggt ltservice name"BNQuoteService"gt ltdocument
ationgtReturns price of a book at BN.com given an
ISBN numberlt/documentationgt ltport
name"BNQuotePort" binding"tnsBNQuoteBinding"gt
ltsoapaddress location"http//services.xmethods
.net80/soap/servlet/rpcrouter"/gt lt/portgt lt/ser
vicegt lt/definitionsgt
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Mapping WSDL to client
ltmessage name"getPriceResponse"gt ltpart
name"return" type"xsdfloat"/gt lt/messagegt
ltportType name"BNQuotePortType"gt ltoperation
name"getPrice"gt ltinput message"tnsgetPriceRequ
est" name"getPrice"/gt ltoutput
message"tnsgetPriceResponse" name"getPriceRes
ponse"/gt lt/operationgt lt/portTypegt
ltmessage name"getPriceRequest"gt ltpart
name"isbn type"xsdstring"/gt lt/messagegt
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Barnes Noble price example sequence diagram

• This simple example is a prototype for all web
  services

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Web services and state

• Web services are generally described as
  stateless.
• In practice this means that you cannot guarantee
  between interactions that you are interacting
  with the same instance of the servlet.
• While web services are, in themselves, inherently
  stateless they can be made to behave in a
  state-full manner
• By using a database back end
• Using cookies
• etc

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Web services and state 2

• One of the reasons that you may be interacting
  with different instances of a servlet lies in the
  use of web services factories.
• In order to deal with many connections it is
  often useful to have a web services factory
  create instances for each connection rather than
  have a single listening service.

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Design considerations with Web Services

• Granularity
• Traffic

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Granularity

• At what level in the design do we introduce
  services?
• Too low and users are swamped in irrelevant
  detail
• Too high and they cant access the details they
  need

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Example
Inappropriate
Appropriate
Aircraft
Travel agent
Aircraft
Airport flight slots
Airport flight slots
Maintenance cycle
Maintenance cycle
A consideration for both services and operations
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Traffic
Business
Yellow pages service
User
Address
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Traffic 2 Messaging systems

• Depends on the available (dedicated) bandwidth
• Dont want services where very frequent calls are
  required (poss gt 1 per sec)
• Dont want services to carry very large amounts
  of data regularly
• Process locally
• Pass encapsulated groups of data

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Serialisation

• Classes passed over web services are translated
  to XML in transport
• This means that the object at the server is not
  necessarily identical to the object at the client.

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Summary

• Attributes/variables become types
• Methods become operations
• Classes become portType
• Appropriate granularity
• Awareness of network traffic
• Web services objects are serialised as XML