CERN – European Organization for Nuclear Research
IT Department – Administrative Information Services
Service Oriented Architecture
definition and main concepts
Derek Mathieson
IT Department
CERN
Some content from Peter Campbell, ANZ Banking Group Australia
Problem Statement

Promote reuse
– Open architecture

Systems Integration
– Link-up Enterprise Information Systems

Interface with other companies
– B2B transactions and processes

Increase Agility
– Acquisition and/or merger
– Changing Business models
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SOA – A definition from the W3C
Typical characteristics of a SOA:

Logical view
– defined by what a service does

Platform neutral
– often XML based

Description orientation
– service description is machine-processable.

Message orientation
– defined in terms of the messages exchanged between
requester and provider

Granularity
– Coarse-grained

Network orientation
– not an absolute requirement.
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SOA Conceptual Architecture
Service
Broker
(UDDI)
Find
(UDDI Inquiry find_xxx)
Service
Consumer
Client
Bind & invoke
SOAP
Register
(UDDI Publish save_xxx)
Service
Provider
Service
Contract
(WSDL)
Service
XML
Binding Choices:

Static binding
– Not loosely coupled as the consumer will fail if the service is offline

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Dynamic binding
– Can allow runtime failover and load balancing
– Service discovery at runtime can have serious performance issues
– Less commonly used
What are Web Services?
Application 2
Application 1
XML
XML
Applications communicating over the internet using
an agreed message format – encoded as XML
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Packaging – Soap
HTTP Post
SOAP Envelope
SOAP Header
SOAP Body
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Packaging – Soap
<s:Envelope xmlns:s="URN">
<s:Header>
<s:Transaction xmlns:m="URN">
<m:TransactionID> 17389 </m:TransactionID >
</s:Transaction>
</s:Header>
<s:Body>
<n:purchaseOrder xmlns:n=“URN”>
<n:item>socks</n:item>
<n:quantity>1</n:quantity>
<n:unitPrice>3.95</n:unitPrice>
</n:purchaseOrder>
</s:Body>
</s:Envelope>
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Description – WSDL
Web Services Description Language
 “Web Services Description Language
(WSDL) provides a model and an
XML format for describing Web
services.” w3c.org

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Description – WSDL
Types
Messages
Operations
Encoding
Endpoint
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Types
<types>
<schema targetNamespace="stockquote.xsd"
xmlns="XMLSchema">
<element name="TradePriceRequest">
<complexType>
<all>
<element name="tickerSymbol" type="string"/>
</all>
</complexType>
</element>
<element name="TradePrice">
<complexType>
<all><element name="price" type="float"/>
</all>
</complexType>
</element>
</schema>
</types>
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Messages
<message name="GetLastTradePriceInput">
<part name="body"
element="xsd1:TradePriceRequest"/>
</message>
<message name="GetLastTradePriceOutput">
<part name="body"
element="xsd1:TradePrice"/>
</message>
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Operations
<operation name="GetLastTradePrice">
<input message="tns:GetLastTradePriceInput"/>
<output message="tns:GetLastTradePriceOutput"/>
</operation>
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Encoding
<binding name="StockQuoteSoapBinding"
type="tns:StockQuotePortType">
<soap:binding style="document"
transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="GetLastTradePrice">
<soap:operation
soapAction="http://example.com/GetLastTradePrice"/>
<input>
<soap:body use="literal"/>
</input>
<output>
<soap:body use="literal"/>
</output>
</operation>
</binding>
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Endpoint
<service name="StockQuoteService">
<documentation>Stock service</documentation>
<port name="StockQuotePort"
binding="tns:StockQuoteSoapBinding">
<soap:address
location="http://example.com/stockquote"/>
</port>
</service>
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Discovery – UDDI
Universal Description, Discovery and
Integration
 A UDDI Server acts as a registry for
Web Services and makes them
searchable.

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Discovery – UDDI
Inquiry
Publish
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UDDI Registry
Discovery – UDDI
Inquiry
Publish
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UDDI Registry
SOA and Web services

Web services
– delivers key standards for implementing SOA

XML
– Ideal candidate for loosely coupled inter-application data sharing

The WS-* Standards Family
– EAI & B2B
SOA
“The architecture”







Services architecture
Service contract
Message based
Service directory
Protocol independent
Coarse grained






Web services specs
WSDL
SOAP & XML
UDDI
HTTP
Doc literal binding

RPC interactions
 Binary XML
Web services
“The plumbing”
Process orchestration
(WS-BPEL)
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Author: Peter Campbell, ANZ Banking Group Australia
Web Services Framework

The Web Services Framework consists of
the following technologies:
Wire stack
Technologies that determine how a
message is sent from the service
requestor to the service provider
e.g. SOAP. Production
usage. Evolving to cover
advanced messaging
functions
Description
stack
Technologies that allow a common
understanding between service
requestor and service provider
e.g. WSDL. Production
usage. Evolving to cover
security and other
additional functions
Technologies that allow a service
requestor to discover a service
provider
e.g. UDDI. Production
usage for static binding.
Evolving to cover dynamic
binding & discovery
Discovery
stack
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Service implementation

A service is a component built for
reuse by other components in
different execution contexts.
Service Interface
Service
Provides service identification,
definition of parameters, and
passing results back to the
consumer
Implementation details are hidden
from the consumer
Services might need to be able to distinguish
messages from individual consumers and also
be able to correlate those messages into
meaningful conversations.
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Services and business processes

Services can be linked to form business
processes using process orchestration
“Open account for customer”
Business Process
Presentation – user interface
Business Process
Orchestration
Business
Services
Get
customer
details
Get
account
type
Add
account to
customer
Coarse
Grained
Service Orchestration
(Process Orchestration)
Technical
Services
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Locate
customer
record
Check
customer
status
Lookup
account
type
table
Retrieve
account
details
Create
CustomerAccount
record
Fine
Grained
Service Reuse

A service can be reused across multiple channels
Business
services
Presentation
layer
Delivery
Channels
Customer
Service
Account
Enquiry
(staff assisted)
Branch
Get
Account
Balance
Account
Enquiry
(self service)
ATM
Internet
Account
Enquiry
(self service)
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Integration roadmap to SOA
2. Message-based middleware with integration broker
1. Point to point systems
Partner
App A
Partner
App A
(J2EE)
Warehouse
App C
(.Net)
App C
Service Bus / MOM
Adapter
App D
(J2EE)
Legacy
Application
App D
Sales
App B
(.Net)
Sales
App B
Shared
System
Legacy
Application
Adapter
Legacy
System
Finance
Finance
3. Service Oriented Architecture & Enterprise Service Bus
Custom
applications
Internet
Adapter
Adapter
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Legacy
System
Shared
System
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Business
Process
Orchestration
Business Rules
Engine
Enterprise Service Bus
HTTP
Services
Package
applications
Routing
Transformation
Service
(Process)
orchestration
Warehouse
Integration – point to point systems
Partner
Advantages
– Connectivity, some integration
Issues:
–
–
–
–
–
–
–
–
–
–
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App A
Warehouse
App B
Sales
App C
Tightly coupled
Legacy
Legacy
Hard to change
Application
Application
Lack of common interface standards
Finance
Security issues
Limited integration and sharing of data
Single points of failure can bring down whole system
Not asynchronous – poor performance and scalability
Silo-based systems aligned with specific business units
Fine-grained services often not reused across the enterprise
Different integration formats
App D
Message Oriented Middleware
Advantages
– Common application interface (API)
– Provides some abstraction between consumer and provider
– Asynchronous
Warehouse
– Transformation
Partner
App B
App D
– Content-based routing
App A
– Reuse services & transactions
Sales
MOM
App C
Adapter
Issues:
Shared
System
– Proprietary service definition
– Messages dependent on middleware
– External (B2B) connectivity difficult
– Some consumer-channel-message coupling
– Limited service repository and manual registry
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Adapter
Legacy
System
Finance
Service Oriented Architecture & Enterprise Service Bus
Custom
applications
Services
Business
Process
Orchestration
Business
Rules Engine
Enterprise Service Bus
HTTP
Internet
Package
applications
Adapter
Adapter
Legacy
System
Shared
System
Routing
Transformation
Service
(Process)
orchestration
Advantages
–
–
–
–
–
–
–
–
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Service bus implementation
Service definition
Common application interface (API)
Provides some abstraction between
consumer and provider
Asynchronous
Transformation
Content-based routing
Reuse services & transactions
– Integration broker
– Standard service description (via WSDL)
– External (B2B) connectivity simplified via
Web services
– Security and identity management provided
by WS-Security standards
– Support for Event Driven Architecture
What is ESB?

Enterprise Service Bus (ESB) helps
manage large number of services by
providing horizontal value-adds such
as:
– Security
– Transactions
– Reliability
– Service Virtualization
• Load Balancing
• Message Distribution (Fan out and in)
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How does ESB Work?

ESB works by using the extension mechanisms
built into SOAP:
1. Message syntax and semantics can be extended with
headers
2. Messages can be intercepted and worked on by
intermediaries

Headers are not just syntax as in Mail Headers
– Semantics of who may/must process headers allows
standardization of extensions. E.g., WS-Security
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Event Driven Architecture (EDA)

Event Driven Architecture (EDA)
– Event triggered messages
– Sender & Receiver have no knowledge
of each other
– Queued messaging
• Store-and-Forward
• Events published to a topic may be sent to
zero, one or many interested recipients. Publisher
msg1
Subscribe to:
msg1 & msg2
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A
msg1
Subscriber
msg2
Broker
X
Publisher
msg2
Y
SOAP Interaction Patterns
SOAP supports the following four interaction patterns:
1. Request-response
(client to server and back)
3. One way
(from client to server)
Request
Client
Server
Client
One way
Server
Response
2. Notification-response
(server to client and back)
3. Notification
(from server to client)
Notification
Server
Client
Server
Notification
Client
Response
SOAP is able to support both remote procedure call (RPC) and document-style
interactions, in either a synchronous or asynchronous fashion
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Conclusions

SOA
– Is not a NEW idea
• But the pieces are now in place
– Facilitates
• Modular design / architecture

Many implementations
– Commercial & Open Source
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Thank You
For More Information
Browse to:
http://www.w3.org/TR/ws-arch
or Email:
Derek.Mathieson@cern.ch
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