January 29, 2018 Sam Siewert

SE310 Analysis and Design of Software

Systems

Lecture 4, Part-1 – Architectural Design

Architecture and Design Patterns Focus on What is Being Designed and Built OO Has Goal of Design and Software Re-Use – Encapsulation of Data and Operations – Class Hierarchy and Object Instances – Well Understand Use Cases – Well Understand Interaction Between Objects

Study 4 Key System Types 1. Interactive – E.g. GUI, CLI 2. Event Driven – E.g. Anit-lock Breaking System Software 3. Transformational – E.g. Image Processing, Encode/Decode

[MPEG Digital Video, RAID] 4. Transaction Oriented – E.g. DBMS

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Four Common Types of Systems

(a) Interactive subsystem

a

b

c

c

z

y x

a

a/x

b/y c/z

b

(b) Event-driven subsystem

(c) Transformational subsystem (d) Database subsystem

Architectural Design Transition from Requirements, Supports Requirements Analysis, Supports Design Activity Focus on Domain Analysis, Use Cases and Higher Levels of System Rather than Details UML – Use Cases – Interaction Diagrams – Class Diagrams – Basic Class Hierarchy (Draft of Class Definitions)

SA/SD – Dataflow, ER/EER Diagrams, High Level State Machines (Flowcharts are Typically Too Detailed)

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Traditional SA/SD – Useful, But Not OO Data Flow Diagrams – Data [Messages] Between Processes and is Transformed Entity Relationship Diagrams – Lacks Operations, but Defines Entities [Objects] and Relationships State Machines [in Common, but Typically for Each Process in DFD] Flow-Charts – Detailed Procedural Design [Interaction, Logic] Sam Siewert 5

Stores, Flows, Processes, External Entities

http://en.wikipedia.org/wiki/Finite-state_machine

http://en.wikipedia.org/wiki/Data_flow_diagram

http://en.wikipedia.org/wiki/Entity%E2%80%93relationship_model

http://en.wikipedia.org/wiki/Flowchart

Domain Models – Use Case Details

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Start Here! https://www.modelio.org/

OMG UML 2.5 Standard Structural Diagrams

• Start with Class Diagram and CRC • Then Object Diagram • Package and Deployment

Behavioral Diagrams

• Start with Use Case Diagram • Interaction Sequence Diagram after

Class and Object Done • Add State Machine and Activity

Diagrams for concurrency and statefulness

Helpful Validation and Verification Features for Design

• Integrated Models • Checklists – Completeness • CPP and Java Code Generation

USE Modelio 3.7 SD as your DESIGN TOOL

UML is Universal Modeling Language [OMG, UML.org] Use to Support Requirements Analysis

Tool-Based Activities Bring Up Modelio and Start Entering ATM Design – Use Case and Class Diagram, Compare to UML Reference Versions of UML – 2.5 Current, UML 2.5 Spec, UML General Minute Paper #2 – Do Design Tools Really Assist with Software Quality Assurance?

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Key Takeaway Points

• Domain modeling is a conceptualization process to help the development team understand the application domain.

• Five easy steps: collecting information about the application domain; brainstorming; classifying brainstorming results; visualizing the domain model using a UML class diagram; and performing inspection and review.

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Acquiring Requirements

(Domain Modeling)

Software architecture

Domain Modeling in the Methodology Context

Deriving Use Cases from Requirements

Allocating Use Cases & Subsystems to Iterations

Business goals & needs

Current situation

Preliminary requirements

Abstract & high level use cases, use case diagrams

Use case-iteration allocation matrix

(a) Planning Phase control flow data flow control flow & data flow

(b) Iterative Phase – activities during each iteration

Actor-System Interaction Modeling

Domain Modeling

Accommodating Requirements Change

Behavior Modeling & Responsibility Assignment

Deriving Design Class Diagram

Test Driven Development, Integration, & Deployment

Customer feedback

Iteration use cases

Domain model

Expanded use cases & UI design

Behavior models

Design class diagram

Domain model

Use case-iteration allocation matrix

Producing an Architecture Design

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feedback

Architectural Design Process

Review the Architectural

Design Specify Subsystem Functions, Interfaces & Interaction Behavior

Determine Design Objectives

Determine Type of System

Apply an Architectural Style

Perform Custom Architectural Design

Types of System & Characteristics

Architectural Styles Repository

design objectives

[architectural style available]

[architectural style not available]

partial design

partial design

Assignment #2 – Domain Models Learning Objectives – Value of UML for Requirements Analysis – Completeness – Design Walk-throughs – Validation [Are We Building the Right Thing?] – Verification [Are We Building it Right?]

New Design, Client-Server [Cloud] Architectural Pattern Storage-as-a-Service – The Competition, E.g. Drop-Box, Amazon S3, Google Cloud

Storage – The Concept – Archive for Unstructured Files (Photos,

Documents, Bits…), Not Code, Not DBMS

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The Requirements – Capabilities Focus 1. Store Any Number of Files (name space) Up to N

Gbytes in an Archive, Browse on Web or Windows, Mac, Linux File Explorer

2. Protect with RAID Against Single Erasure (Covered in CS317, SE420)

3. Submit and Retrieve Any File by Name, Time and Date Archived (In Case of Duplicate Names)

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Assignment #2 Goals Consistent and Complete UML Design – Domain Model Focus -Ready for Validation and Verification Walkthrough Ideally Capable of C++ or Java Class Code Generation We Will Walk-through Design for Assignment #3 More In Depth Use of Modelio or ArgoUML Better Understanding of UML 2.4 – Use Case, Component, Class, Interaction Diagrams [2 From Behavior Side, 2 From Structure Side of UML] Sam Siewert 13

CRC – Class Responsibility Collaborator [SE300 Review]

Create a Set of Index Cards with Proposed Classes, Responsbilities for the Class and Collaborators (has an Association Useful Step Prior to Class Diagram and Class Definitions Not Officially Part of UML, but Useful Supporting Method Sam Siewert 14

http://www.uml.org.cn/umlapplication/pdf/crcmodeling.pdf

SE300 Week-5 slides #7 - #18

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Domain Modeling Steps

3. Classifying brainstorming result

1.Collecting application domain information

2. Brainstorming

4. Visualizing the domain model 5. Reviewing the

domain model.

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Tip for Domain Modeling

4) Have a member or two to convert the result to a UML class diagram.

6) Modify the diagram to reflect corrections and comments.

Do not do brainstorming and drawing at the same time. The result could be very poor.

1) Team brainstorming: List the concepts, and then classify them on a whiteboard.

2) Take a picture(s) of the whiteboard using a digital camera.

3) Email the digital images to team members.

5) Email the UML class diagram to all members to review.

RAID Archive Systems - Multiple Disk Drives

Disk Drives Fail – Like a Light-bulb – MTBF of 100’s of Thousands of Hours [3 to 5 Years at Duty

Cycle] – Difficult to Determine When Failure Might Occur – The Larger the Population, the More Often Failures will be Seen

Disk Drives Have Low Random Access [100 to 200 I/Os per Second] Idea – Write to them in Parallel and Mirror Data to Protect Against HDD Failures (Erasures)

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RAID-10

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A1 A1 A2 A2 A3 A3 A4 A4 A5 A5 A6 A6

RAID-1 Mirror RAID-1 Mirror RAID-1 Mirror

RAID-0 Striping Over RAID-1 Mirrors

A7 A7 A8 A8 A9 A9 A10 A10 A11 A11 A12 A12

A1,A2,A3, … A12

RAID Operates on LBAs/Sectors (Sometimes Files)

SAN/DAS RAID NAS – Filesystem on top of RAID RAID-10, RAID-50, RAID-60 – Stripe Over Mirror Sets – Stripe Over RAID-5 XOR Parity Sets – Stripe Over RAID-6 Reed-Soloman or Double-Parity Encoded

Sets

EVEN/ODD Row Diagonal Parity Minimum Density Codes (Liberation) Reed-Solomon Codes

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RAID5,6 XOR Parity Encoding

MDS Encoding, Can Achieve High Storage Efficiency with N+1: N/(N+1) and N+2: N/(N+2)

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0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Stor

age

Effic

ienc

y

Number of Data Devices for 1 XOR or 2 P,Q Encoded Devices

RAID6

RAID5

RAID-50

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A1

RAID-5 Set RAID-5 Set

B1 C1 D1 P(ABCD)

E1 F1 G1 H1 P(EFGH)

I1 J1 P(IJKL) K1 L1 M1 P(MNOP) N1 P1 O1

P(QRST) Q1 R1 S1 T1

A2 B2 C2 D2 P(ABCD)

E2 F2 G2 H2 P(EFGH)

I2 J2 P(IJKL) K2 L2 M2 P(MNOP) N2 P2 O2

P(QRST) Q2 R2 S2 T2

RAID-0 Striping Over RAID-5 Sets

A1,B1,C1,D1,A2,B2,C2,D2,E1,F1,G1,H1,…, Q2,R2,S2,T2

RAID is an Erasure Code

RAID-1 is an MDS EC (James Plank, U. of Tennessee)

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Read, Modify Write Penalty Any Update that is Less than the Full RAID5 or RAID6 Set, Requires 1. Read Old Data and Parity – 2 Reads 2. Compute New Parity (From Old & New Data) 3. Write New Parity and New Data – 2 Writes Only Way to Remove Penalty is a Write-Back Cache to Coalesce Updates and Perform Full-Set Writes Always

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A1

RAID-5 Set

B1 C1 D1 P(ABCD)

E1 F1 G1 H1 P(EFGH)

I1 J1 P(IJKL) K1 L1 M1 P(MNOP) N1 P1 O1

P(QRST) Q1 R1 S1 T1

Write A1,B1,C1,D1, E1,F1,G1,H1,… P(ABCD)new=A1new xor A1 xor P(ABCD) A1 B1 C1 D1 P(ABCD) 0 0 0 0 0 0 0 0 1 1 0 0 1 0 1 0 0 1 1 0 0 1 0 0 1 0 1 0 1 0 0 1 1 0 0 … 1 1 1 1 0

XOR parity Indicates Odd number Of “1’s”

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What Is a Model?

• A conceptual representation of something. • A schematic description of a system, theory, or

phenomenon that accounts for its known or inferred properties and may be used for further study of its characteristics. (Dictionary Definition)

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An ancient Chinese story. How four blind men perceive an elephant.

Why Do We Need Model?

We perceive the world differently due to differences in backgrounds and viewpoints. Modeling facilitate collective understand of the application.

Elephant is like a wall.

No, elephant is like a rope.

No, I think elephant is a cylinder.

No, you are all wrong. Elephant is like a fan.

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Represent Domain Model as UML Class Diagram

• UML class diagram is a structural diagram. • It shows the classes, their attributes and

operations, and relationships between the classes.

• Domain model is represented by a class diagram without showing the operations.

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SSN: char*

checkin(time:float):void

name: char*

checkout(time:float):void

Employee

Representing Type in UML

general syntax name : type

attribute name

function name parameter name parameter type

return type

attribute type

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Features (i.e., attributes and operations) defined

for the super-class are automatically defined for the subclasses.

Example: Inheritance

A staff is a user, a student is a user.

User id: char*

login(id, password) name: char*

logout()

Staff Student

applyOnline() processApplication()

superclass, it is more general

subclass, more specific

triangle pointing to the super-class.

subclass may have additional features

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Two Tests for Inheritance

Engine model# horse power manufacturer start() stop()

Car drive()

• IS-A test: every instance of a subclass is also an instance of the superclass.

• Conformance test: relationships of a superclass are also relationships of subclasses.

Professor name phone teach(...)

Visiting Professor

signContract()

Retirement Plan

enroll

Visiting professors cannot enroll in a retirement plan at the host university.

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Aggregation Relationship

• It expresses the fact that one object is part of another object.

• Example: engine is part of a car.

• It is also called part-of relationship.

Car Model # horse power Manufacturer start() stop()

Engine Model # horse power Manufacturer start() stop()

part-of relationship

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Association Relationship

• It expresses a general relationship other than inheritance and aggregation.

• These can be application specific relationships between two concepts.

• Example: "instructor teach course," "user has account." Professor

name phone teach(...)

Retirement Plan

enroll

Enroll is not an inheritance or aggregation relationship.

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Student Course enroll �

student course

teach

course

instructor

Faculty

Faculty teaches Course

Student enrolls in Course

Role and Association Direction

association name

association direction

role name

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Role and Multiplicity

Employee

supervise

supervisor

worker *

Employee supervises other employees.

Another employee is the worker.

An employee is the supervisor.

A supervisor supervises zero or more employees.

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User

Staff User

+ Name + Address + Phone No + e - mail ID + User Name + Password + Privilege

Search

+ Program Type + Acedamic Subject + Region + Country + Language

Program

+ Program Type + Academic Subject + Term of Study + Language of Instruction + Country + Region + Application Deadline + Fees + Scholarships & Financial aid

Administrator

Manages 1 ..*

0 ..*

Performs 1 ..*

0 ..* Online Application

+ Program Name + Student Name + Student ID + Address + Course

Submits 1

1 ..*

- Application

- Student

Feedback

+ Description Submits

- Student

- Feedback

1 ..*

1

* For 0 ..*

1

Manages

1

1 ..*

For 0 ..*

1

On

0 ..*

0 ..*

Sample Domain Model

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Key Takeaway Points

• The software architecture of a system or subsystem refers to the style of design of the structure of the system including the interfacing and interaction among its subsystems and components.

• Different types of systems require different design methods and architectural styles.

Copyright {c} 2014 by the McGraw-Hill Companies, Inc. All rights Reserved.

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Acquiring Requirements

Software architecture

Architectural Design in Methodology Context

Deriving Use Cases from Requirements

Allocating Use Cases & Subsystems to Iterations

Business goals & needs

Current situation

Preliminary requirements

Abstract & high level use cases, use case diagrams

Use case-iteration allocation matrix

(a) Planning Phase control flow data flow control flow & data flow

(b) Iterative Phase – activities during each iteration

Actor-System Interaction Modeling

Domain Modeling

Accommodating Requirements Change

Behavior Modeling & Responsibility Assignment

Deriving Design Class Diagram

Test Driven Development, Integration, & Deployment

Customer feedback

Iteration use cases

Domain model

Expanded use cases & UI design

Behavior models

Design class diagram

Domain model

Use case-iteration allocation matrix

Producing an Architectural Design

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What Is Software Architectural Design

• The software architecture of a system or subsystem refers to the style of design of the structure of the system including the interfacing and interaction among its major components.

• Software architectural design is a decision-making process to determine the software architecture for the system under development.

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Characteristics of Interactive Systems • The interaction between system and actor consists of a

relatively fixed sequence of actor requests and system responses.

• The system has to process and respond to each request. • Often, the system interacts with only one actor during the

process of a use case. • The actor is often a human being although it can also be a

device or another subsystem. • The interaction begins and ends with the actor. • The actor and the system exhibit a “client-server”

relationship. • System state reflects the progress of the business process

represented by the use case.

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Characteristics of Event-Driven Systems • It receives events from, and controls external entities. • It does not have a fixed sequence of incoming requests;

requests arrive at the system randomly. • It does not need to respond to every incoming event. Its

response is state dependent—the same event may result in different responses depending on system state.

• It interacts with more than one external entity at the same time.

• External entities are often hardware devices or software components rather than human beings.

• Its state may not reflect the progress of a computation. • It may need to meet timing constraints, temporal

constraints, and timed temporal constraints.

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Characteristics of Transformational Systems • Transformational systems consist of a network of

information-processing activities, transforming activity input to activity output.

• Activities may involve control flows that exhibit sequencing, conditional branching, parallel threads, synchronous and asynchronous behavior.

• During the transformation of the input into the output, there is little or no interaction between system and actor—it is a batch process.

• Transformational systems are usually stateless. • Transformational systems may perform number

crunching or computation intensive algorithms. • The actors can be human beings, devices, or other

systems.

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Characteristics of Object-Persistence Systems

• It provides object storage and retrieval capabilities to other subsystems.

• It hides the implementation from the rest of the system.

• It is responsible only for storing and retrieving objects, and does little or no business processing except performance considerations.

• It is capable of efficient storage, retrieval, and updating of a huge amount of structured and complex data.