January 20, 2016 Sam Siewert

SE310Analysis and Design of Software

Systems

Lecture 3 – Systems Requirements

Learning ObjectiveSoftware Engineering Process? – Lifecycle Phases

Agile – Manifesto that Hosts Spiral, XP, Scrum, Feature-Driven or any Iterative Process [Waterfall with Feedback]Requirements? Architecture? – First Phase is Research, Analysis and Specification Sam Siewert 2

SPIRAL in Agile XP – ExtremeIn Agile

WATERFALL

feedback

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

2-3

CH2 - Rational Unified Process (RUP)• Inception consists of the first 1-2 iterations. It

produces a simplified use case model, a tentative architecture, and a project plan.

• Elaboration consists of the next N iterations. It produces the architectural design and implements the most critical use cases.

• Construction, during which remaining use cases are iteratively implemented and integrated into the system.

• Transition, during which the system is deployed, users are trained, and defects are corrected.

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

2-4

CH2 - Rational Unified Process (RUP)

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

2-5

Agile Process Models

phas

es in

an

itera

tion

Iterations

Traditional SA/SD – Useful, But Not OOData Flow Diagrams – Data [Messages] Between Processes and is Transformed

Entity Relationship Diagrams – Lacks Operations, but Defines Entities [Objects] and Relationships

SE300

State Machines [in Common, but Typically for Each Process in DFD]

Flow-Charts – Detailed Procedural Design [Interaction, Logic]

Sam Siewert 6

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 with UML - CASEUML is Universal Modeling LanguageUse to Support Requirements Analysis

Sam Siewert 7

Start Here!

https://www.modelio.org/

http://argouml.tigris.org/

Helpful Validation and Verification Features for Design

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

WARNING: ArgoUML has bugs, so use only to review Argo design examples

USE Modelio as your DESIGN TOOL

Architecture and Design PatternsOO 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 Types1. Interactive – E.g. GUI, CLI2. Event Driven – E.g. Anit-lock Breaking System Software3. Transformational – E.g. Image Processing, Encode/Decode

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

Sam Siewert 8

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

2-9

Software Paradigm• A software paradigm is a style of software

development that constitutes a way of viewing the reality.

• Examples: – procedural paradigm– OO paradigm, and– data-oriented paradigm

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

2-10

Three Paradigms in History• Procedural paradigm views the world and system as:

– a network of processes– a process is refined by lower level processes– basic building blocks and starting point are processes

• OO paradigm views the world and system as:– interrelated and interacting objects– basic building blocks are objects

• Data-oriented paradigm views the world and system as:– interrelated data entities, processed by transactions– basic building blocks are data entities and relationships

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

2-11

Structured Design

Object-Oriented AnalysisStructured Analysis

Object-Oriented Design

Data-Oriented Analysis

Procedural Paradigm OO Paradigm

Structured Programming

Object-Oriented Programming

Data-Oriented Paradigm

Data-Oriented Design

Programming in

4GL (e.g., SQL)

Paradigm and Methodology

ProcessOrders

Books

Customers

orders

invoices(w/books) credit status

Customer

Top Manager

BE

B E

A

CF

Top Decider

DG

GC F D

H

Class - 1attrib 1attrib 2

Class - 2attrib 1attrib 2

Class - 3attrib x

Domain model

Student

Student

enroll

sn

sname

cn

cname

Obj: class b : Bclass

m1 ( ) m2 ( ) m3 ( )

m4 ( )m5 ( )info

m6 ( ) m7 ( ) m8 ( )

m9 ( )m10 ( )Sequence diagram

Tool-Based ActivitiesBring Up Modelio and Start Entering ATM Design – Use Case and Class Diagram, Compare to UML Reference

Versions of UML – 2.4.1 Current

Minute Paper #2 – Do Design Tools Really Assist with Software Quality Assurance?

Sam Siewert 12

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

2-13

Methodology Overview – Planning Phase

Deriving Use Cases from Requirements

Allocating Use Cases &to Iterations

Acquiring Requirements & Domain Modeling

Business goals & needs Current situation

Requirements

Abstract & high level use cases, use case diagrams

Use case-iteration allocation matrix

Producing an Architecture Design

Software architecture

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

2-14

AccommodatingRequirements Change

Methodology Overview – Iterative Phase

Deriving Design Class Diagram

Actor-System Interaction Modeling & UI Design

Domain Modeling

Behavioral Design

TDD, Integration, & Deployment

Iteration use cases

Domain model

Expanded use cases & UI design

Behavior diagrams

Design class diagram

Domain model

Use case-iteration allocation matrix Software architecture

Assignment #2 – Domain ModelsLearning 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

Sam Siewert 15

The Requirements – Capabilities Focus1. 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)

Sam Siewert 16

Assignment #2 GoalsConsistent and Complete UML Design 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 17

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

3-18

Key Takeaway Points• System engineering is a multidisciplinary

approach to systems development. • System engineering defines the system

requirements and constraints, allocates the requirements to the hardware, software, and human subsystems, and integrates these subsystems to form the system.

• Software engineering is a part of system engineering.

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

3-19

System Architectural Design

• Decomposing the system into a hierarchy of functional cohesive, loosely coupled subsystems, which partition the system requirements and facilitate reuse of COTS components.

• System requirements are assigned to the subsystems.

Decomposing the System

Allocating System Requirements

Visualizing System Architecture

• The system architecture is depicted usinga certain diagramming technique.

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

3-20

Requirements Allocation

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

3-21

Architectural Design Diagrams• Block diagram• UML component diagram• SysML diagrams• Data flow diagram• and more ...

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/Osper Second]

Idea – Write to them in Parallel and Mirror Data to Protect Against HDD Failures (Erasures)

Sam Siewert 22

RAID-10

Sam Siewert 23

A1 A1 A2 A2 A3 A3A4 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 A9A10 A10 A11 A11 A12 A12

A1,A2,A3, … A12

RAID Operates on LBAs/Sectors (Sometimes Files)

SAN/DAS RAIDNAS – Filesystem on top of RAIDRAID-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/ODDRow Diagonal ParityMinimum Density Codes (Liberation)Reed-Solomon Codes

Sam Siewert 24

RAID5,6 XOR Parity Encoding

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

Sam Siewert 25

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

Sam Siewert 26

A1

RAID-5 Set RAID-5 Set

B1 C1 D1 P(ABCD)E1 F1 G1 H1P(EFGH)I1 J1 P(IJKL) K1 L1

M1 P(MNOP) N1 P1O1P(QRST) Q1 R1 S1 T1

A2 B2 C2 D2 P(ABCD)E2 F2 G2 H2P(EFGH)I2 J2 P(IJKL) K2 L2M2 P(MNOP) N2 P2O2

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)

Sam Siewert 27

Read, Modify Write Penalty

Any Update that is Less than the Full RAID5 or RAID6 Set, Requires1. Read Old Data and Parity – 2 Reads2. 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

Sam Siewert 28

A1

RAID-5 Set

B1 C1 D1 P(ABCD)E1 F1 G1 H1P(EFGH)I1 J1 P(IJKL) K1 L1

M1 P(MNOP) N1 P1O1P(QRST) Q1 R1 S1 T1

Write A1 P(ABCD)new=A1new xor A1 xor P(ABCD)

A1 B1 C1 D1 P(ABCD)0 0 0 0 00 0 0 1 10 0 1 0 10 0 1 1 00 1 0 0 10 1 0 1 00 1 1 0 0…

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

3-29

UML Component Diagram

air link

instructionsHigh-Power Transceivers

Controller Hardware

Base Station

Mobile Units

Base Station Antenna Account

ManagementController Software

Mobile Hardware

Mobile Software

events

events

instructionscall data

portLegend: component stereotype for introducing new modeling constructs

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

3-30

Data Flow Diagram with Material Flows

Receiving Dock

valid shipment

slipVerify Shipment Content

Purchasing

1shipment

slip Classify Publications

Received

Cataloging

2

Handle Documents

Check-In/Out

Circulation

3new titles available

Cataloging Room

Book Shelves

raw shipment publications publications w/call numbers

Legend:

material flow

information flow

Function

Subsystem

IDExternal

EntityInternal Entity

Publisher