1 1 lecture 2 concepts of software architecture purposes/objectives major elements of s/w...

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Lecture 2 Concepts of Software Architecture

• Purposes/Objectives• Major Elements of S/W Architecture• Architecture Framework• Architectural Models/Patterns• Architecture Case Study

Software Architecture & Design Pattern

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Software Architecture

A high level abstraction and description to the structure and organization of software system, also a blueprint for software development and evolution.

Software Architectural Model

An expression of the viewpoint of software architecture, which is a rich, rigorous, and structural description on the software system’s elements, functions and interface.


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Why need software architectural model?


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Better? en ... not quite yet

Segment(from ssi)

AttributeDescription(from serializati...

ResourceDescription(from serializati...

HttpCredential(from ht...

PlainRemoteResource(from adm...

HtmlHead(from ht...

SampleMuxHandler(from m...

Stresser(from tes...

JigsawHttpSessionContext(from servl...

HtmlStyle(from ht...

AdminContext(from admin)

AuthUserPrincipal(from a...

IPMatcherNode(from au...

HttpBag(from ht...

HtmlGenerator(from ht...

DirectoryResource(from resourc...

FileResource(from resourc...

HttpEntityTag(from ht...

HttpManager(from ht...

CGIHeaderHolder(from fram...

Shuffler(from ht...

IndexersCatalog(from index...

ResourceIndexer(from index...

MuxClientFactory(from m...

ResourceContext(from resourc...

EventManager(from time...

ResourceStoreManager(from sto...

PropertySet(from conf...

FramedResource(from resourc...

ServerHandlerManager(from daem...

AdminWriter(from adm...

Serializer(from serializati...

RequestTimeout(from ht...

MimeType(from mime)

IPMatcher(from auth)

ExternalContainer(from resourc...

PICS(from pi...

SSIFrame(from s...

SSIStream(from s...

ArrayDictionary(from ut...

CommandRegistry(from comman...

VariantState(from NegotiatedFra...

SampleResourceIndexer(from index...

ProtocolFrame(from frames)

MimeClientFactory(from ht...

MimeParser(from mi...

DAVMimeClientFactory(from webd...

ResourceException(from resourc...

SocketOutputBuffer(from sock...

DebugThread(from sock...

ThreadCache(from ut...

SocketClientFactoryStats(from sock...

httpd(from http)

MuxSession(from m...

ResourceFilter(from resources)

HttpMimeType(from ht...

HttpTokenList(from ht...

ResourceReference(from resources)

HTTPPrincipal(from a...

ProxyRequestObserver(from pro...

ProfileRef(from cc...

HttpExtList(from ht...

Client(from http)

CCPPRequest(from cc...


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Much better --- your boss

would like to see

Hardware Abstraction Layer

Linux kernelperformance-differentiatedkernel scheduler

Cluster Applications

RTCS Application Framework API

Linux System Call

RTCSQueue

RTCSDispatcher

RTCSScheduler

RTCSMonitor

RTCSForwarder

RTCSEvent

RTCSClassifier


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Purposes/Objectives

• Identify critical components/subsystems of software system

• Describe relationship/interaction/interface of the components• Guide software design and bridge design and implementation• Identify key techniques/tools to implement software system


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Software Design Principles

• Decomposition and decoupling• Architectural model• Component interface/relationship• Data/object abstraction• Communication/network interface• Concurrency: multiprocess vs. multithread• Scalability


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Identify Major Components/Subsystems

• Component/Subsystem: a group of software units collectively providing certain function or service (module in C++ or package in Java)

• Organize or lay out functional units of a software system --- various architectural models

• Identify core modules/components or common features


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RTCS Architectural Model

Hardware Abstraction Layer

Linux kernelperformance-differentiatedkernel scheduler

Cluster Applications

RTCS Application Framework API

Linux System Call

RTCSQueue

RTCSDispatcher

RTCSScheduler

RTCSMonitor

RTCSForwarder

RTCSEvent

RTCSClassifier

Major Components

• upper application

• RTCS Framework

- storage class

- service class

- utility class

• O/S system call API

Major Functions• cluster resource management

• real-time scheduling

• responsive service


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Relationship/Interface among Components

• Structural relationship

• Functional relationship

• Abstract class vs. Interface class

• Communication interface

- TCP/IP sockets

- RPC (Remote Procedure Call),

RMI (Remote Method Innovation)

- message passing


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CORBA Architecture for Distributed System


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Interface between Components


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Guidance of Software Design

• Deposition of System - decoupling of data and presentation - spread functions among components - multiprocess or multithread

• Interface Design - external interface vs. internal interface - interface definition language/schema

• Interaction in Components/Subsystems - service consumer vs. service provider - synchronous call vs. asynchronous call - interaction protocols


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Internet Protocol Design

- use layered architectural model to show the design

Win2K Linux LynxOS

Solaris VxWorks

Middleware

MiddlewareServices

MiddlewareApplications

MIDDLEWARE ARCH

21st Century

RTP

DNS

HTTP

UDP TCP

IP

NET

Ethernet ATM FDDI

Fibre Channel

FTP

INTERNETWORKING ARCH

TFTP

20th Century


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Decomposition of System

- Decoupling an avionics system

Context Problems Solution

• I/O driven DRE application

•Complex dependencies

•Real-time constraints

•Tightly coupled components

•Hard to schedule

•Expensive to evolve

•Apply the Publisher-Subscriber architectural pattern to distribute periodic, I/O-drivendata from a single point of source to a collection of consumers


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How to decouple functional units

Event

*

Subscriber

consume

creates receives

Event Channel

attachPublisher detachPublisherattachSubscriberdetachSubscriberpushEvent

Filter

filterEvent

Publisher

produce

Structure

attachSubscriberproduce

pushEventevent

eventpushEvent

consume

detachSubscriber

: Event

: Subscriber: Event Channel: Publisher

Dynamics


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Context Problems Solution

•Mission computing requires remote IPC

•Stringent DRE requirements

•Applications need capabilities to:•Support remote communication•Provide location transparency•Handle faults•Manage end-to-end QoS•Encapsulate low-level system details

•Apply the Broker architectural pattern to provide platform-neutral communication between mission computing boards

Use architectural model to improve communication system design


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Platform-neutral and network-transparent communication architecture

operation (params)connect

send_request

marshal

unmarshaldispatch

operation (params)

result

marshal

receive_replyunmarshal

result

start_upregister_service

assigned port

Dynamics

: Broker: Client Proxy : Object Adapter: Client : Server


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Identify key techniques and development tools

• OOAD / CASE tool• Distributed System / Communication Protocols• Component-based / Interface• Concurrency / Multithreading• SOA / J2EE• 3-D / Graphics Toolkit• Real-Time / RTOS


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Major Elements of Architectural Model

• Elements/Connectors/Data - components (simple vs.

composite) - subsystems - layers

• Architectural Topology (diagrams) - configuration/layout

• Interaction/Association - component interface - communication interface - relationship


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Major elements – Component

A software component is an architectural building block that encapsulates a subset of functions and data, and restricts access to them via an explicitly defined interface.


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Major elements – Connector

A software connector is an architectural building block tasked with regulating interactions among components.

connector examples

- Procedure call connectors

- Shared memory connectors

- Message passing connectors

- Streaming connectors

- Distribution connectors

- Wrapper/adaptor connectors


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Major elements – Topology

The architectural topology captures architectural structure via graphs whose nodes representing components and connectors and edges representing interconnectivity.

Projectrepository

Designtranslator

Programeditor

Designeditor

Codegenerator

Designanalyser

Reportgenerator


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Interaction between Components


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Architecture Framework

A set of architectural views, design patterns, and methodology based on a certain type of architectural model

• 4+1 Views

• Zachman Framework

• DODAF (Dept. of Defense Architectural Framework)

• TOGAF (The Open Group Architecture Framework)

• RM-ODP (Reference Model of Open Distributed Processing)


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4+1 View Model/Framework

• Logic View

• Process View

• Deployment View

• Physical View

• Scenarios (Use Case)


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Logical View

Physical ViewProcess View

Development View

End user

System EngineerIntegrator

Programmers& software managers

Scenarios


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Logical View

Viewer: End-userConsiders: Functional requirements- What the system should provide in terms of services to its users. Notation: Class diagramTool: CASE tool


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Logical View – class view


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Logical View – sequence diagram


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Logical View – communication diagram


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Logical View – state diagram


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Development View

Viewer: programmers and managers

Considers: software module organization

Style: layered style

Notation: UML


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Process View

Viewer: integrator

Considers: Non - functional requirements

(concurrency, performance, scalability)

Style: several styles


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Process View example


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Physical View

Viewer: system engineer

Considers: non-functional requirements regarding

hardware (computing node, network)

Notation: costumed


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Physical View example


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Scenarios

Viewer: all users of other views and evaluators.Considers: system consistency, validityNotation: UML/Use CaseTool: CASE tool


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Scenarios – Use Case diagram


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Questions?


1 1 lecture 2 concepts of software architecture purposes/objectives major elements of s/w...

Documents

corba architecture

bridge design

software development

software systems elements

group of software units

components multiprocess

service module

various architectural