9. Architecture Venkat Subramaniam Arch-1 Whats Architecture? - - PDF document

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Venkat Subramaniam

• 9. Architecture

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What’s Architecture?

• Description of sub-system

– Components/sub-systems – Their interaction

• Framework for communication

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Architectural Design

• Establishes a basic structural framework
• Identifies major components of a system
• Communication between them

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Why do you need it?

• Useful for communication
• Helps analyze ability to meet

requirements

• Leads to repeatable, reusable concepts

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Issues to deal with

• Potentially conflicting issues
• Performance
• ✁✄✂☎✂✝✆✟✞✡✠☞☛✌✂✝✂✎✍✟✏✒✑✓✞✔✂✎✕✗✖✙✘✛✚✝✜✢✖✤✣✥✖✦✞✡✂✎✧✩★✪✠✫✧✟✧✟✘✎✑✎✏✬★✦✭✮✞✯✏

• Security

• Safety/validation
• ✁✄✂☎✂✝✆✟✞✡✠❑✏✬✖✦✠✛✶✬✭✮✞✔✂✰✏✒✑☎✞✡✠▲✠✛✑✮✂❇✠✛✕✗✭▲✷❍✂☎❄▼✖✿✘✛✚✝✜✢✖✤✣✥✖✦✞✔✂✎✧■✖
• Availability/reliability/redundancies

• Maintainability

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Architectural Representation

• Block diagrams generally used
• Effective to communicate different sub-

systems

• Not effective to describe sub-system

interface

• Goal: design so that requirement change

does not propagate across several sub- systems

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Developing Architectural Design

• Very creative process
• Job of a system architect
• Varies based on system, experience,

requirements

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General Questions

• Questions and considerations
• Do we have a template to start with?
• Style
• System structure
• Sub-system decomposition
• Measure of quality
• Documentation

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Models

• Client-server model
• Layered model
• Combined style
• Static Structure Model
• Dynamic Process Model

– Processes at runtime

• Interface Model

– Sub-system interface

• Relationship Model

– Dataflow, communication, …

• Distribution Model

– Distribution across processors, computers

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Organization

• Decided by
• Data
• Services
• Functional

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Repository

• Considerations

– Efficiency – Format of data – Data Usage – Change to format – Centralization and maintenance – Force on the sub-systems Central Storage Message Passing

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• May be on one box
• May be across machines
• May be physical distribution or simply

logical

Client-Server Model

Client Server Different services: File, Printing, Computation, …

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Layering

• How do we structure the application in a

way that it is maintainable, robust, reliable, secure and robust?

• Separate the components into layers
• The layers will have loose coupling
• Each layer is cohesive
• Components in a layer interact with

– Components within the layer – Components in layer below it

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Layering …

• In a strict layering, components do not

talk to any layer other than the one below it

• In a more relaxed layering, components

may bypass one or two layers below

Layer n Layer n Layer 3 Layer 2 Layer 1

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Tier Distribution

• Layering is more logical
• Tier distribution talks about how the

application is distributed across different hardware

• The physical tiers is composed of

different computers that share:

– Resources

• Like sockets, disc space, etc.

– Operational requirements

• Security, scalability,

– Constraints

• Location may be dictated by constraints like

security

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Three-Tier Distribution

Client Tier Application Tier (Business Tier) Data Tier

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