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7/29/2019 Unit I SOA
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04.05.2011 Unit 1
Service Oriented ArchitectureUNIT – I
Based On
Service-Oriented Architecture: Concepts,Technology, and Design
By
Thomas Erl
Prepared By
S.Usha & J.Jeyalakshmi
Lecturer / Department of Information TechnologyRajalakshmi Engineering College
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04.05.2011 Unit 1
Roots of SOA (comparing SOA to past architectures)
• What is architecture?
– IT departments started to recognize the need for a standardized definition of
a baseline application that could act as a template for all others.
– This definition was abstract in nature, but specifically explained the
technology, boundaries, rules, limitations, and design characteristics that
apply to all solutions based on this template.
– This was the birth of the application architecture.
Types Of Architecture:
1. Application architecture
2. Enterprise architecture
3. Service-oriented architecture
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Application architecture
Application architecture is to an application development team what a blueprint is to ateam of construction workers.
Different organizations document different levels of application architecture.
Some keep it high-level, providing abstract physical and logical representations of
the technical blueprint. Others include more detail, such as common data models,
communication flow diagrams, application-wide security requirements, and aspects of
infrastructure.
It is not uncommon for an organization to have several application architectures.
A single architecture document typically represents a distinct solution environment.For example, an organization that houses both .NET and J2EE solutions would verylikely have separate application architecture specifications for each.
A key part of any application-level architecture is that it reflects immediate solution
requirements, as well as long-term, strategic IT goals.
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Enterprise architecture
• In larger IT environments, the need to control and direct IT infrastructure is critical.
• When numerous, disparate application architectures co-exist and sometimes even integrate, thedemands on the underlying hosting platforms can be complex and onerous.
• Therefore, it is common for a master specification to be created, providing a high-level overviewof all forms of heterogeneity that exist within an enterprise, as well as a definition of thesupporting infrastructure.
• Continuing our previous analogy, an enterprise architecture specification is to an organization
what an urban plan is to a city. Therefore, the relationship between an urban plan and the blueprint of a building are comparable to that of enterprise and application architecturespecifications.
• Typically, changes to enterprise architectures directly affect application architectures, which is
why architecture specifications often are maintained by the same group of individuals.
Further ,enterprise architectures often contain a long-term vision of how the organization plans toevolve its technology and environments.
For example, the goal of phasing out an outdated technology platform may be established in thisspecification.
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Service-oriented architecture
service-oriented architecture spans both enterprise and application architecturedomains.
The benefit potential offered by SOA can only be truly realized when appliedacross
multiple solution environments.
This is where the investment in building reusable and interoperable services based
on a vendor-neutral communications platform can fully be leveraged. This does notmean that the entire enterprise must become service-oriented.
SOA belongs in those areas that have the most to gain from the features andcharacteristics it introduces.
Note that the term "SOA" does not necessarily imply a particular architectural
scope. An SOA can refer to an application architecture or the approach used tostandardize technical
architecture across the enterprise.
Because of the composable nature of SOA (meaning that individual application-level architectures can be comprised of different extensions and technologies), it isabsolutely possible for an organization to have more than one SOA.
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Characteristics of SOA
The following primary characteristics:
1. Contemporary SOA is at the core of the service-oriented computing platform.
2. Contemporary SOA increases quality of service.
3. Contemporary SOA is fundamentally autonomous.
4. Contemporary SOA is based on open standards.
5. Contemporary SOA supports vendor diversity.
6. Contemporary SOA fosters intrinsic interoperability.
7. Contemporary SOA promotes discovery.
8. Contemporary SOA promotes federation.
9. Contemporary SOA promotes architecturalcomposability.
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Characteristics of SOA cont…
10.Contemporary SOA fosters inherent reusability.
11.Contemporary SOA emphasizes extensibility.
12.Contemporary SOA supports a service-oriented
business modeling paradigm.
13.Contemporary SOA implements layers of abstraction.14.Contemporary SOA promotes loose coupling throughout
the enterprise.
15.Contemporary SOA promotes organizational agility.
16.Contemporary SOA is a building block.17.Contemporary SOA is an evolution.
18.Contemporary SOA is still maturing.
19.Contemporary SOA is an achievable ideal
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Characteristics of SOA
• Service-oriented software architecture has these characteristics Bieber and
Carpenter 2001, Stevens, Service-Oriented, 2002, Sun Microsystems, Jini
Technology Architectural Overview 2001):
• Services are discoverable and dynamically bound.
• Services are self-contained and modular.
• Services stress interoperability.
• Services are loosely coupled.
• Services have a network-addressable interface.
• Services have coarse-grained interfaces.
• Services are location-transparent
• Services are composable.
• Service-oriented architecture supports self-healing.
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04.05.2011 Unit 1
SOA vs Traditional Distributed Internet Architecture
• Muliple client-server architectures have appeared
• Client-server DB connections have been replacedwith Remote Procedure Call connections (RPC) using
CORBA or DCOM• Middleware application servers and transaction
monitors require significant attention
• Multi-tiered client-server environments began
incorporating internet technology in 90s.
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SOA vs Traditional Distributed Internet Architecture
• The browser shifted 100% of application logic to the
server
• Distributed Internet architecture introduced the Web
server as a new physical tier • HTTP replaced RPC protocols
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SOA vs Traditional Distributed Internet Architecture
• Distributed Internet application put all the applicationlogic on the server side
• Even client-side scripts are downloaded from the
server • Entire solution is centralized
• Emphasis is on:
– How application logic is partitioned
– Where partitioned units reside
– How units of logic should interact
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SOA vs Traditional Distributed Internet Architecture
• Difference lies in the principles used to determine the
three primary design considerations
• Traditional systems create components that reside on
one or more application servers• Components have varying degrees of functional
granularity
•
Components on the same server communicate via proprietary APIs.
• RPC protocols are used across servers via proxy stubs
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SOA vs Traditional Distributed Internet Architecture
• Actual references to other physical components can
be embedded in programming code (tight coupling)
• SOAs also rely on components
• Services encapsulate components
• Services expose specific sets of functionality
• Functionality can originate from legacy systems or
other sources
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SOA vs Traditional Distributed Internet Architecture
• Functionality is wrapped in services
• Functionality is exposed via open, standardized
interface, irrespective of technology providing the
solution• Services exchange information via SOAP messages.
SOAP supports RPC-style and document-style
messages
• Most applications rely on document-style
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SOA vs Traditional Distributed Internet Architecture
• Messages are structured to be self-sufficient
• Messages contain meta information, processing
instructions, policy rules
• SOA fosters reuse on a deep level by promotingsolution-agnostic services
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Comparing SOA to client-server anddistributed internet architectures
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Client-Server Application Technology
• The technology set for client-server applicationsincluded 4GLs like VB and PowerBuilder, RDBMSs
• The SOA technology set has expanded to include
Web technologies (HTML, CSS, HTTP, etc)• SOA requires the use of XML data representation
architecture along with a SOAP messagingframework
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Client-Server Application Security
• Centralized at the Server level
• Databases manage user accounts and groups
• Also controlled within the client executable
• Security for SOA is much more complex
• Security complexity is directly related to the degree
of security measures required
• Multiple technologies are required, many in WS-Security framework
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04.05.2011 Unit 1
Client-Server Application Administration
• Significant maintenance costs associated with client-
server
• Each client housed application code
• Each update required redistribution
• Client stations were subject to environment-specific
problems
•
Increased server-side demands on databases
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Client-Server Application Administration
• SOA solutions are not immune to client-sidemaintenance challenges
• Distributed back-end supports scalability, but new
admin demands are introduced• Management of server resources and service
interfaces may require new admin tools and even a private registry
•
Commitment to services and their maintenance mayrequire cultural change in an organization
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04.05.2011 Unit 1 23
Logic components of the Web services
framework
• Web services contain
one or more operations.
• Figure 8.4 as anexample
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Logic components of the Web services
framework
• Each operation governs
the process of a specific
function the web service
is capable of performing.
• Figure 8.5 gives an
example of an operation
sending and receiving
SOAP messages
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Logic components of the Web
services framework
• Web services form an
activity though which
they can collectively
automate a task.
• Figure 8.6 as an
example
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Logic components of
automation logic• Fundamental parts of
the framework
– SOAP messages
– Web service operations
– Web services
– Activities
• Renamed terms
– Messages
– Operations
– Services
– Processes
• Activity has been changed because it uses a different context
when modeling service-oriented
business processes.
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Logic components of
automation logic• Messages = units of communication
• Operations = units of work
• Services = units of processing logic
• Processes = units of automation logic
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Logic components of
automation logic• The purpose of these
views is to express the
process, services and
operations.
• Is also provides a flexible
means of partitioning and
modularizing the logic.
• These are the most basic
concepts that underliesservice-orientation.
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04.05.2011 Unit 1 29
Components of an SOA
• Message
– A message represents the data required to
complete some or all parts of a unit of work.
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Components of an SOA
• Operation
– An operation represents the logic required to process
messages in order to complete a unit of work .
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Components of an SOA
• Service
– A service represents a logically grouped set of
operations capable of performing related units of
work.
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Components of an SOA
• Processes
– A process contains the business rules that determine which
service operations are used to complete a unit of
automation.
– A process represents a large piece of work that requires the
completion of smaller units of work .
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How components in an SOA inter-
relate
• An operation sends and receives messages to
perform work.
• An operation is therefore mostly defined by
the message it processes.
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How components in an SOA inter-
relate
• A service groups is a collection of related
operations.
• A service is therefore mostly define by the
operations that comprise it.
i i
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How components in an SOA inter-
relate• A process instance can compose service.
• A process instance is not necessarily defined by itsservice because it may only require a subset of the
functionality offered by the services.
• A process instance invokes a unique series of operations to complete its automation.
• Every process instance is therefore partially defined bythe service operation it uses.
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Key Points
• The logical parts of an SOA can be mapped tocorresponding components in the basic Web servicesframework.
• By viewing a service-oriented solution as a unit of
automation logic, we establish that SOA consists of asophisticated environment that supports a highlymodularized separation of logic into differently scopedunits.
• SOA further establishes specific characteristics, behaviors, and relationships among these componentsthat provide a predictable environment in support of service-orientation.
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04.05.2011 Unit 1
COMMON PRINCIPLES OF
SERVICE- ORIENTATION
38
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Common principles of service-
orientation• Services are reusable
• Services share a formal contract
• Services are loosely coupled
• Services abstract underlying logic
• Services are composable
•
Services are autonomous
• Services are stateless
• Services are discoverable
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04.05.2011 Unit 1 40
Services are reusable
• Regardless of weather immediate reuse
opportunities exist, services are designed to
support potential reuse.
• Service-oriented encourages reuse in all
services.
• By applying design standards that require
reuse accommodate future requirements with
less development effort.
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Services are reusable
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Case Study
•
RailCo created the Invoice Submission Servicewhich contains two operations
– SubmitInvoice
– GetTLSMetadata
• SubmitInvoice - Allows RailCo send
electronic invoices to TLS Account Payable
Service
• GetTLSMetadata – checks periodically for
changes to TLS Account Payable Service
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Case Study
• In Plain English
– Business License Office provides a distinct
service
• Issuing business licenses
• Renewing business licenses
– Provides service to all customers• Classifies this service as reusable
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04.05.2011 Unit 1 44
Services share a formal contract
• For services to interact, they need not
share anything but formal contract that
describe each service and define the
terms of information exchange.
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04.05.2011 Unit 1 45
Services share a formal contract
• Service contracts provide a formal definitionof:
– The service endpoint
– Each service operation – Every input and output message supported by each
operation
– Rules and characteristics of the service and its
operations
• Service contacts define almost all of the primary parts of an SOA.
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Services share a formal contract
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Case Study
• RailCo and TLS agreed to a service contract
that allow the two companies to communicate
• TLS defined the definition of the associated
service description documents
• TLS ensures a standardized level of
conformance that applies to each of its online
vendors
• TLS can change the service at any time
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Case Study
• In Plain English
Application form is needed obtain or renew a
business license
– Application formalizes the request in a standard
format for the Business License Office
– Application is a contract between the business and
Business License Office
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Services are loosely coupled
• Services must be designed to interact without
the need for tight, cross-service dependencies.
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Services are loosely coupled
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Case Study
• TLS services are designed to communicate
with multiple online vendors make it loosely
coupled
• RailCo service are designed to communicate
only with TLS B2B system so is considered
less loosely coupled
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Case Study
• In Plain English
– Once the Application is submitted no further
action is required on the business
– Business and Business License Office remain
independent
– Application is the only requirement tocommunicate with Business License Office
Services abstract underlying
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Services abstract underlying
logic• The only part of a service that is visible to
the outside world is what is exposed via
the service contract. Underlying logic,
beyond what is expressed in thedescriptions that comprise the contract, is
invisible and irrelevant to service
requestors.
Services abstract underlying
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Services abstract underlying
logic
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Case Study
• RailCo Web services hide the underlying
legacy code need to produce the invoices
that are needed to sent to TLS
• TLS Web services hide the underlyingservices that process the invoices from
multiple online vendors
• Neither service requestor require anyknowledge of what processes are working
on the other’s service providor
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Case Study
• In Plain English
– Business License Office tasks are hidden
from the business
– Business does not care what Business
License Office does, it just wants a license
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Services are composable
• Services may be compose other services. This
allows logic to be represented at different
levels of granularity and promotes reusability
and the creation of abstraction layers.
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Services are composable
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Case Study
• TLS accounts Payable Service is composed on
three services
– Accounts Payable Service
– Vendor Profile Service
– Ledger Service
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Case Study
• In Plain English
– Other government agencies can use the Business
License Office for their license tasks
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THANK YOU