16.453 / 16.553 Software Engineering University of Massachusetts at Lowell Class Meeting #5 Instructor: Joe Russell Website:

16.453 / 16.55316.453 / 16.553Software EngineeringSoftware Engineering

University of Massachusetts at LowellUniversity of Massachusetts at Lowell

Class Meeting #5Class Meeting #5

Instructor: Joe RussellInstructor: Joe RussellWebsite: http://www.geocities.com/joe_programmingWebsite: http://www.geocities.com/joe_programming

16.453 / 16.553 Software Enginee16.453 / 16.553 Software Engineeringring

22

Case StudiesCase Studies

Structured Analysis and Structured Analysis and Structured DesignStructured Design


33

TopicsTopics

Case Study: Automating a Law OfficeCase Study: Automating a Law Office Case Study: Incremental DeliveryCase Study: Incremental Delivery Structured Analysis / Structured DesignStructured Analysis / Structured Design


44

Case StudyCase Study

Automating a Law OfficeAutomating a Law Office


55

Case Study: Case Study: Automating a Law OfficeAutomating a Law Office

Leaders of a SW Company realized that law Leaders of a SW Company realized that law offices such as title companies were poorly offices such as title companies were poorly automatedautomated

They felt a need for an integrated office They felt a need for an integrated office automation tool could lead to more efficiency in automation tool could lead to more efficiency in the law officethe law office Standard headers in documentsStandard headers in documents Pull relevant data out of a database Pull relevant data out of a database Calculate fields within a documentCalculate fields within a document Etc…Etc…


66


Market AnalysisMarket Analysis Contacted personal acquaintances in the field Contacted personal acquaintances in the field

to determine whether they would be interested to determine whether they would be interested in the product.in the product.

Contacted members of a professional Contacted members of a professional committee to see whether there was interest committee to see whether there was interest in the productin the product

Asked for feedback as to which features Asked for feedback as to which features would be most desireablewould be most desireable


77


Market Analysis (cont’d)Market Analysis (cont’d) Although the SW Company’s behavior seems Although the SW Company’s behavior seems

natural, there are problems with the analysisnatural, there are problems with the analysis• Sample of potential customers selected was Sample of potential customers selected was

biased. It did not represent a scientific sampling of biased. It did not represent a scientific sampling of the market.the market.

• Market analysis was performed by “pure software Market analysis was performed by “pure software engineers” who had little background in the engineers” who had little background in the marketing fieldmarketing field


88


Economic and Financial PlanningEconomic and Financial Planning Requires the ability to forecast future sales Requires the ability to forecast future sales

and the ability to estimate costsand the ability to estimate costs• Influenced by one’s knowledge of both the price at Influenced by one’s knowledge of both the price at

which the product can be sold and the number of which the product can be sold and the number of items solditems sold

It was difficult for the SW Company to perform It was difficult for the SW Company to perform this analysis because it was driven by SW this analysis because it was driven by SW engineers who were technically savvy but not engineers who were technically savvy but not economically and financially competenteconomically and financially competent


99


Economic and Financial Planning (cont’d)Economic and Financial Planning (cont’d) Difficulty in estimating cost is that SW doesn’t Difficulty in estimating cost is that SW doesn’t

necessarily get produced faster simply by adding necessarily get produced faster simply by adding more people to the projectmore people to the project

No risk analysis was performedNo risk analysis was performed No precautions were taken to control any known No precautions were taken to control any known

critical activitiescritical activities When it was apparent that the estimates were flawed, When it was apparent that the estimates were flawed,

nobody proposed a plan to correctnobody proposed a plan to correct• Only day-by-day actions were undertakenOnly day-by-day actions were undertaken

The lesson? Short-term decisions overwhelm long-The lesson? Short-term decisions overwhelm long-term planning … this is a very common management term planning … this is a very common management mistake!mistake!


1010


Technical Planning and ManagementTechnical Planning and Management No analysis was performed to determine whether all No analysis was performed to determine whether all

of the product’s features were neededof the product’s features were needed Anticipation of change principle was not considered in Anticipation of change principle was not considered in

the designthe design Strong pressure was applied to have code running as Strong pressure was applied to have code running as

early as possibleearly as possible No precautions taken to minimize damages due to No precautions taken to minimize damages due to

personnel turnoverpersonnel turnover


1111


Technical Planning and Management Technical Planning and Management Designers were attracted by the most interesting Designers were attracted by the most interesting

features of the new productfeatures of the new product Sophisticated features for the automatic computation Sophisticated features for the automatic computation

of invoices were designed, but no attention was paid of invoices were designed, but no attention was paid to standard office operations, e.g., filing large number to standard office operations, e.g., filing large number of documents.of documents.

Supposedly the employees in the company knew they Supposedly the employees in the company knew they were making these classical SE mistakes, but were making these classical SE mistakes, but nonetheless the mistakes were made.nonetheless the mistakes were made.


1212


Project MonitoringProject Monitoring After six months, some technical and After six months, some technical and

management mistakes became apparentmanagement mistakes became apparent• Lack of clear definition of product’s functionalityLack of clear definition of product’s functionality• Some important features had been neglectedSome important features had been neglected• Getting in touch with more potential users showed Getting in touch with more potential users showed

that not all the features were needed … since the that not all the features were needed … since the architecture was not modular, this posed problemsarchitecture was not modular, this posed problems


1313


• Project Monitoring (cont’d)Project Monitoring (cont’d)• How did the SW Company attempt to fix these How did the SW Company attempt to fix these

project problems?project problems?• More effort put forth to try to fix the problemsMore effort put forth to try to fix the problems• SW patches were made wildlySW patches were made wildly• No systematic error and correction logs were kept No systematic error and correction logs were kept

in order to save timein order to save time• Communication among designers occurred almost Communication among designers occurred almost

exclusively orally in an attempt to save timeexclusively orally in an attempt to save time


1414


• Project Monitoring (cont’d)Project Monitoring (cont’d)• Manager’s Attitude? Since “we are almost Manager’s Attitude? Since “we are almost

done,” “we just need a little more financing done,” “we just need a little more financing and can accept almost any terms.”and can accept almost any terms.”

• What could have been done?What could have been done?• A critical and careful analysis of the mistakes that A critical and careful analysis of the mistakes that

were done in the projectwere done in the project• A replanning and/or redesign of the project as a A replanning and/or redesign of the project as a

wholewhole


1515


Initial DeliveryInitial Delivery It was decided that income could be generated by It was decided that income could be generated by

delivering “first versions” of the product or as soon as delivering “first versions” of the product or as soon as new contracts could be signednew contracts could be signed

• In return, the customer might be a good reference resulting in In return, the customer might be a good reference resulting in increased salesincreased sales

This backfired because many of the early customers This backfired because many of the early customers had problems with the product since the product was had problems with the product since the product was never clearly definednever clearly defined

• This caused internal problems because it was not clear This caused internal problems because it was not clear whether the activity fell under product development or user whether the activity fell under product development or user assistanceassistance


1616


Partial RecoveryPartial Recovery Eventually it was realized the managing of the Eventually it was realized the managing of the

project was leading to disaster. Steps were project was leading to disaster. Steps were made to prevent disaster:made to prevent disaster:• Responsibilities were clearly defined as to who Responsibilities were clearly defined as to who

was responsible for whatwas responsible for what• Effort made to achieve a clear picture of the state Effort made to achieve a clear picture of the state

of the product and what was required to fix itof the product and what was required to fix it The above was done at the expense of The above was done at the expense of

slowing down the project, increasing costs, slowing down the project, increasing costs, and reducing salesand reducing sales


1717


Partial Recovery (cont’d)Partial Recovery (cont’d)How did things go?How did things go?

• People had to resist an initial feeling that the People had to resist an initial feeling that the restructuring of the project was impeding “real” progress.restructuring of the project was impeding “real” progress.

• Over time, improvements became apparentOver time, improvements became apparent

• Eventually, the company produced a product with full Eventually, the company produced a product with full documentationdocumentation

• The company shipped the product and earned money The company shipped the product and earned money although it was far less than initially expected due to the although it was far less than initially expected due to the delay of the introduction of the productdelay of the introduction of the product


1818


Lessons LearnedLessons Learned Good intuition and technical skills are not Good intuition and technical skills are not

enough to guarantee successenough to guarantee success Marketing analysis and process organization Marketing analysis and process organization

must be planned carefully before committing must be planned carefully before committing to the projectto the project

Changes in schedules and project sourcing Changes in schedules and project sourcing after serious problems are encountered can after serious problems are encountered can be difficult and expensive, if not impossible to be difficult and expensive, if not impossible to implementimplement


1919

Case StudyCase Study

Incremental DeliveryIncremental Delivery


2020

Case Study: Case Study: Incremental DeliveryIncremental Delivery

A computer manufacturer was building a A computer manufacturer was building a new computernew computer HWENG working on HW D&DHWENG working on HW D&D SWENG working on SW D&DSWENG working on SW D&D

• The company decided to use Pascal for all its The company decided to use Pascal for all its software developmentsoftware development

• The company was going to need to develop a The company was going to need to develop a Pascal compiler with extensions to overcome Pascal compiler with extensions to overcome weaknesses of existing Pascal compilersweaknesses of existing Pascal compilers


2121


The company’s language group took a poll The company’s language group took a poll of the software engineers to see what of the software engineers to see what extensions would be needed.extensions would be needed. The Result? Every language feature ever The Result? Every language feature ever

discovered was proposed by at least one discovered was proposed by at least one person as absolutely necessary for the person as absolutely necessary for the product!product!


2222


The poll results made it clear that the The poll results made it clear that the compiler, with all extensions, could not be compiler, with all extensions, could not be delivered by the time other groups were delivered by the time other groups were ready to start coding.ready to start coding.


2323


The language group decided to use the The language group decided to use the principle of incrementalityprinciple of incrementality The group ranked the needed extensionsThe group ranked the needed extensions The group scheduled three releases of the The group scheduled three releases of the

compiler: standard Pascal, Pascal with compiler: standard Pascal, Pascal with minimal extensions, Pascal with all other minimal extensions, Pascal with all other extensionsextensions


2424


ExtensionsExtensions The extensions were first prototyped by The extensions were first prototyped by

implementing a preprocessor for an existing implementing a preprocessor for an existing Pascal compilerPascal compiler• Was slow and inefficient, but allowed the Was slow and inefficient, but allowed the

engineers to use the extensions and provide engineers to use the extensions and provide feedback to the language group as to the usability feedback to the language group as to the usability of the extensionsof the extensions


2525


Hardware ArrivesHardware Arrives By this time, a Pascal compiler with minimal By this time, a Pascal compiler with minimal

extensions is availableextensions is available• Allowed engineers to start implementing their Allowed engineers to start implementing their

software (OS & database) using the compilersoftware (OS & database) using the compiler• Many people had earlier versions of their software Many people had earlier versions of their software

already developed and tested from the prototype already developed and tested from the prototype compiler … a simple recompile was all that was compiler … a simple recompile was all that was necessarynecessary


2626


After Six Months …After Six Months … The language group took another poll of the The language group took another poll of the

software engineers and found that NO other software engineers and found that NO other extensions were needed!extensions were needed!

However, since the original list didn’t include However, since the original list didn’t include efficiency-related extensions, a new extension efficiency-related extensions, a new extension was added to aid in the efficiency (logical was added to aid in the efficiency (logical operations on integers)operations on integers)


2727


Over Time …Over Time … Several other compiler releases occurredSeveral other compiler releases occurred

• More sophisticated level of code optimizationMore sophisticated level of code optimization• More extensions addedMore extensions added

Incremental Delivery allowed users to Incremental Delivery allowed users to have access to useful functionality and have access to useful functionality and allowed the compiler developers to allowed the compiler developers to enhance the compiler on the basis of enhance the compiler on the basis of explicit and definitive user feedback!explicit and definitive user feedback!


2828


Lessons LearnedLessons Learned Prototyping is possiblePrototyping is possible A throw-away prototype may be used by A throw-away prototype may be used by

clients to start on their project while they await clients to start on their project while they await the final productthe final product

A throw-away prototype enables parallel A throw-away prototype enables parallel development by clients and developersdevelopment by clients and developers

A throw-away prototype may be used to prune A throw-away prototype may be used to prune an initial set of requirements on the basis of an initial set of requirements on the basis of actual usage and need for features.actual usage and need for features.


2929

Organizing The Software ProcessOrganizing The Software Process

Organizing the software process is a Organizing the software process is a critical activity involving everything from critical activity involving everything from the management of people to the the management of people to the management of all productsmanagement of all products Involves definition of appropriate methods and Involves definition of appropriate methods and

their combination within methodologiestheir combination within methodologies


3030

Methods and MethodologiesMethods and Methodologies

According to Webster’s New World According to Webster’s New World Dictionary (1977):Dictionary (1977): Method – A way of doing anything, especially Method – A way of doing anything, especially

in an orderly wayin an orderly way Methodology – A system of methodsMethodology – A system of methods


3131

Appeal of MethodologiesAppeal of Methodologies

Methodologies that guide programmers in Methodologies that guide programmers in their work in all phases of development:their work in all phases of development: Increase people’s confidence in what they are Increase people’s confidence in what they are

doingdoing Teaches inexperience people how to solve Teaches inexperience people how to solve

problems in a systematic wayproblems in a systematic way Encourages a uniform, standard approach to Encourages a uniform, standard approach to

problem solvingproblem solving


3232

Structured Analysis / Structured Analysis / Structured Design (SA/SD)Structured Design (SA/SD)

In Requirements an Analysis phase, SA/SD In Requirements an Analysis phase, SA/SD suggests three major conceptual tools for suggests three major conceptual tools for constructing system modelsconstructing system models Data Flow Diagrams (DFDs)Data Flow Diagrams (DFDs)

• Used for specifying the functional requirements of the systemUsed for specifying the functional requirements of the system Data Dictionaries (DDs)Data Dictionaries (DDs)

• Centralized definitionsCentralized definitions Structured English (SE)Structured English (SE)

• To describe transformation of terminal bubblesTo describe transformation of terminal bubbles

SA/SD is Function-Oriented and its modules SA/SD is Function-Oriented and its modules represent functional abstractionsrepresent functional abstractions


3333

Data Flow DiagramData Flow Diagram

Used for specifying the functional requirements Used for specifying the functional requirements of the systemof the system Function represented by bubblesFunction represented by bubbles Data flows represented by arrowsData flows represented by arrows

• direction is with respect to the range of the function direction is with respect to the range of the function represented by the bubblerepresented by the bubble

Data stores are represented by open boxesData stores are represented by open boxes• two horizontal lines with data store name enclosedtwo horizontal lines with data store name enclosed

Input/Output represented by special I/O boxesInput/Output represented by special I/O boxes• Describe data acquisition and generation during human-Describe data acquisition and generation during human-

computer interactioncomputer interaction


3434

Data Flow DiagramData Flow Diagram

A file

Adata

transformer

An output deviceAn input

device


3535

Employee_1

Registration

Employee_2

Authorization

Employee_3

Response

Request

Request

Result

Authorized_requests

Employee_4Employee_6

Employee_5

Process ProcessProcess

Order_request

Complete_order

Analysis ofoffice work


3636

Extract order data

Get letter form

Order request

Letter form

Letter forms

Quantity to order

Type of letter

Compose order

Get address

Addresses

Address

Addressee

AddressComplete order

Authorized requests

AutomatedPortion of Office Work


3737

From Analysis and From Analysis and Requirements to DesignRequirements to Design

The preceding DFDs specify the functional The preceding DFDs specify the functional requirements of the office workrequirements of the office work

The “Design”, i.e., the decomposition of The “Design”, i.e., the decomposition of the system into modules, is based directly the system into modules, is based directly on the DFDs and is documented using on the DFDs and is documented using Structured Diagrams (SDs)Structured Diagrams (SDs)


3838

Structured DiagramsStructured Diagrams

A Structured Diagram is a Directed Acyclic A Structured Diagram is a Directed Acyclic Graph (DAG)-like structureGraph (DAG)-like structure Nodes represent modulesNodes represent modules Each module represents a functional abstraction to be Each module represents a functional abstraction to be

implemented later by a subprogramimplemented later by a subprogram

The method to transform DFDs into SDs should The method to transform DFDs into SDs should aim to:aim to: minimize couplingminimize coupling maximize cohesionmaximize cohesion


3939

Structured DiagramsStructured Diagrams

SDs may be decorated with additional SDs may be decorated with additional notationsnotations Show parameter flow between modules by Show parameter flow between modules by

arrow and parameter namearrow and parameter name Show control patterns governing the calls of Show control patterns governing the calls of

subordinate modulessubordinate modules• Diamond represents selection between modules to Diamond represents selection between modules to

callcall• Curved arrow represents loops of calls to a moduleCurved arrow represents loops of calls to a module


4040

Structured DiagramsStructured Diagrams A Directed Acyclic Graph of functional modules

Direction of arrow is implicitly downward

M

MMM 1 32


4141

Decorated Structured DiagramDecorated Structured DiagramM

MMM 1 32

M 1,1 M 1,2

XX Y

Y

X XX

11

M1 abstract inputM2 transformationM3 abstract output


4242

Decorated Structured DiagramDecorated Structured Diagram

Order main

Get data

Produce data for order form

Print order form

T

Q

AE

AE

T

A

L

A

L

Q

SD for the “Automated Portion" DFDSD for the “Automated Portion" DFD

LEGENDLEGENDT = Type of LetterT = Type of LetterQ = QuantityQ = QuantityAE = AddresseeAE = AddresseeL = Letter FormL = Letter FormA = AddressA = Address

Documents

16.453 / 16.553 Software Engineering University of Massachusetts at Lowell Class Meeting #5 Instructor: Joe Russell Website: