erect关于软件开发的知识(中英文)

1. What is software development?

Software development is the process of developing software through

successive phases in an orderly way. This process includes not only the

actual writing of code but also the preparation of requirements and

objectives,

the

design

of

what

is

to

be

coded,

and

confirmation

that

what

is developed has met objectives.

Before systems development methods came into being, the development of

new

systems

or

products

was

often

carried

out

by

using

the

experienceand

intuition of management and technical personnel. However, the

complexityof

modern

systems

and

computer

products

long

ago

made

the

need

clear forsome kind of orderly development process.

Typical phases of software development:

1) Identification of required software

2) Analysis of the software requirements

3) Detailed specification of the software requirements

4) Software design

5) Programming

6) Testing

7) Maintenance

In general, the development of commercial software is usually a result

of demand in the marketplace, while enterprise software

developmentgenerally

arises

from

a

need

or

a

problem

within

the

enterprise

environment.

2. How is software development guided?

The software development process is almost invariably guided bysome

systematic

software

development

method

(SDM).

Referred

to

by

a

numberof

terms, including

process models

,

development guidelines

,and

systems

development life cycle models

(SDLC), software development methods

nevertheless generally include the same development phases:

The

existing

system

is

evaluated

and

its

deficiencies

identified,

usually through interviewing system users and support personnel.

?

The new system requirements are defined. In particular, the

deficiencies

in

the

existing

system

must

be

addressed

with

specific

proposals for improvement.

?

The

proposed

system

is

designed.

Plans

are

laid

out

concerning

the

physical construction, hardware, operating systems, programming,

communications, and security issues.

?

The new system is developed. The new components and programs must

be obtained and installed. Users of the system must be trained in

its

use,

and

all

aspects

of

performance

must

be

tested.

If

necessary,

adjustments must be made at this stage.

?

The system is put into use. This can be done in various ways. The

new system can phased in, according to application or location,

andthe

old

system

gradually

replaced.

In

some

cases,

it

may

be

more

cost- effective to shut down the old system and implement the new

system all at once.

?

Once

the

new

system

is

up

and

running,

then

it

should

be

exhaustively

evaluated. Maintenance must be kept up rigorously at all

of

the

system

should

be

kept

up-to-date

concerning

the

latest modificationsand procedures.

?

The systems development life cycle model was developed as a structured

approach to information system development that guides all the

processesinvolved from an initial feasibility study through to

maintenance of thefinished application. SDLC models take a variety of

approaches to development.

Systems development life cycle models include:

·

The

waterfall

model:

This

is

the

classic

SDLC

model,

with

a

linear

and

sequential

method

that

has

goals

for

each

developmentphase.

The

waterfall

model simplifies task scheduling, because there areno iterative or

overlapping

steps.

One

drawback

of

the

waterfall

is

thatit

does

not

allow

for much revision.

·

Rapid

application

development

(RAD):

This

models

based

on

the

concept

that

better

products

can

be

developed

more

quicklyby:

using

workshops

or

focus

groups

to

gather

system

requirements;

prototyping

and

reiterative

testing of designs; rigid adherence to schedule; and less formality of

team communications such as reviews.

·

Joint application development (JAD):

This modelinvolves the client

or

end

user

in

the

design

and

development

of

an

applicationthrough

a

series

of collaborative workshops called

JAD sessions

.

·

The prototyping model:

In this model, a prototype (an early

approximation of a final system or product) is built, testedand then

reworked as necessary until an acceptable prototype is finallyachieved

from which the complete system or product can now be developed.

·

Synchronize-and-stabilize:

This model involves teams working in

parallel on individual application modules, frequently synchronizing

their code with that of other teams and stabilizing code frequently

throughout the development process.

· The spiral model:

This model of development combines the features of

the

prototyping

model

and

the

waterfall

model.

The

spiral

model

is

favored

for large, expensive, and complicated projects.

3. How has the open source development process influenced software

development in general?

Open

source

software

is

developed

collaboratively;

source

code

is

freely

available

for

use

and

modification.

The

open

source

movement

arose

because

some developers came to believe that competition amongst vendors leads

to inferior products and that the best approach to development isa

collaborative one.

The OSI (Open Source Initiative) is an industry body that certifies

products as open source if they conform to a number of rules:

· The software being distributed must be redistributed to anyone else

without any restriction

· The source code must be made available (so that the receiving party

will be able to improve or modify it)

· The license can require improved versions

of the software to carry a

different name or version from the original software

Despite

its

emphasis

on

the

collaborative

process,

the

biggest

influence

that

open

source

has

had

on

software

development

in

general

may

be

through

competition:

by

competing

with

proprietary

software

products,

open

source

products

force

vendors

to

work

that

much

harder

to

hold

their

market

share

in the face of viable open source alternatives.

4.

What

are

some

generally

accepted

best

practices

common

to

all

or

most

development models?

Here's a collection of some of the top tips from a variety of industry

sources:

· Make sure that you've chosen a systems development life cycle model

that suits your project, because every one of the processesinvolved

depends

on

the

model.

That

said,

however,

implementing

any

modelis

better

than

none

--

much

of

the

success

of

a

project

depends

upon

howscrupulously

the model is adhered to.

· Reuse software components when it's appropriate, but don't use code

that

doesn't

work

perfectly

for

its

intended

purpose

just

because

you

have

it on hand.

·

Be

very

thorough

in

gathering

requirements,

ensuring

that

all

parties

agree on what they are -- and make sure you document them.

·

Don't

promise

the

moon,

if

you

can't

deliver

it.

Avoidletting

someone

who isn't fully informed negotiate with the client.

· Make sure that the architecture you've chosen is appropriate for the

application

you're

building.

To

retain

perspective,

you

might

want

to

look

at the smaller picture and plan the architecture incrementally.

·

Change is part of life, including software development. You have to

accept

that

various

things --

requirements,

for

example --

are

likely

to

change

throughout

the

life

of

the

project.

Keep

control

of

them,

but

not

too rigidly.

· Set up peer review process

es for every element of the project.

·

Design

thoroughly

and

with

care,

but

remember

the

KISSprinciple:

Keep

it simple.

·

In

your

project

plan,

split

big

projects

into

manageable

chunks,

with

concrete milestones and deadlines.

· Ensure accountability: make

sure that deadlines are clear and that

people have to report on whether they made them, and explain why not if

they don't.

· Implement quality control procedures throughout the project.

· Test exhaustively

-- there's no point in doing a cursory run through

only to have an application fail when you run it for the client.

· After the project is completed, conduct a thorough post

-mortem, with

everyone involved. You'll see what worked well and what should havebeen

differently, and your future projects will benefit.

5. What are some common mistakes in software development?

According to a Standish Group report, corporations in the United States

spend

over

$$275

billion

every

year

on

software

development

projects,

many

of

which

are

doomed

to

failure.

Research

by

the

group

found

that

over

80%

of

projects

fail

for

various

reasons,

and

that

fully

30%

of

projectswere

cancelled prior to completion because of poor execution.

David

B.

Stewart,

at

the

University

of

Maryland,

set out

to

document

the

10

most

common

mistakes

of

software

development.

He

found,

however,that

the

sheer

number

of

errors

that

were

commonly

practiced

made

it

impossible

to

keep

the

number

to

ten.

He

ended

up

calling

his

article

Common

Mistakes

with

Real-Time

Software

Development.

Even

so,

afterthe

title had been established, he found another five errors so common that

the felt compelled to add them.

According to Dr. Michael, the most common project problems are due to

failure to manage project elements successfully:

· Requirement

s are not clearly and accurately defined, and agreed upon

by all concerned.

· Resources are not adequately planned and allocated.

· Threats to project success are not clearly detected, identified, and

protected against.

· Critical path analysis is omitted,

or poorly executed.

· The project's progress is not tracked adequately.

·

Quality

management

is

not

carried

out

well

enough

throughout

the

life

of the project.

·

Too

little

data

is

collected,

or

data

is

ignored

or

poorly

understood.

Correcting

flaws

identified

during

software

security

audits

is

expensive

and time consuming. Worse, vast resources are spent on containing and

recovering

from

exploits.

Fortunately,

providing

development

staff

with

the knowledge and tools to avoid many of these pitfalls is easy and

inexpensive.

6.

Given

a

particular

process

model,

is

there

a

set

of

tools(a

development

environment) to support it?

In general, a process model usually begins as a philosophy of

what

development

when

rather

than

a

rigid

methodology

complete

with

tools.

For

example,

rapid

application

development

(RAD)

is

an

approach

that

can

make

use

of

existing

development

tools.

In

general,

tools

for

supporting

all or part of a process model tend to arrive later, if at all.

Historically,

development

tools

have

focused

on

the

code-building,

code

archive management, documentation, testing, and packaging parts ofthe

process, sometimes offered as a suite. Such a suite is generally known

as an integrated development environment (IDE).

A set of tools for managing or supporting a development project is

generally known as a computer-assisted software environment (CASE). A

number of companies offer products that support early stages of

development

such

as

requirements

gathering,

design

prototyping,

and

data

modeling.

A

number

of

these

provide

tools

that

support

data

modeling

with

the

Unified

Modeling

Language.

Overall,

there

is

a

trend

toward

providing

all or most of the tools for a development project in a single product

or related set of products.

Today,

the

main

code-building

development

environments

or

program

suites

come from Microsoft with its Visual Studio and Visual Studio .NET,

providing

support

for

Visual

Basic,

Visual

C#,

Visual

C++,

and

Visual

J#;

Sun Microsystems with its Java 2 Enterprise Environment; and numerous

software vendors such as Borland who repackage these environments with

some value-added features. Recently, almost all providers of software

development

environments

have

added

features

that

enable

the

software

to

be used on the Web.

7. How

do

you

choose

the

programming

language

for

your project?

For

most

projects,

the

right

language

is

easy

to

choose.

Your

company

may

have standardized on a particular development environment and language

(and you may have been hired because you were already familiar with the

language).

Or

you

may

be

updating

or

enhancing

an

existing

program;

it's

almost

always

best

to

use

the

same

language

the

existing

program

is

written

in.

In

some

cases,

however,

someone

will

need

to

select

the

best

(or,

since

the

best

may

be

somewhat

arguable,

at

least

an

appropriate

language).

In

somecases, you or your team of developers may need to know several

languages fordifferent purposes.

General truisms about programming languages are that: