The Internet Encyclopedia (Volume 3)

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288 SOFTWAREDESIGN ANDIMPLEMENTATION IN THEWEBENVIRONMENT

driven almost entirely by time-to-market; it is almost in-

variably more lucrative to deliver poor-quality products

sooner than high-quality products later. It is a well-known

truism that companies can often sell poor-quality first ver-

sions of software applications and then make more money

by charging for upgrades that contain more bug fixes than

new features. For most applications, there has tradition-

ally been little economic motivation for producing high-

quality software. In fact, there have often been economic

disincentives for creating high-quality software products.

Web-based software is in a completely different situa-

tion, one more akin to critical software such as aerospace,

telecommunications, and medical devices. One of the in-

teresting challenges is that Web software has extremely

high-quality requirements (Offutt 2002; Powell 1998).

However, there appears to be little or no brand-name loy-

alty (that is, “site loyalty”) for Web applications. Many

companies that sell through the Web depend on customers

using their sites, and most important, returning to their

sites. Others offer more traditional software services that

are available through the Web; these services will not be

used if the quality is too low because it is relatively easy

for users to switch to other services. Thus, unlike many

contractors, Web site developers will only see a return on

their investment if their Web sites exhibit sufficient quality

(that is, if the Web sites satisfy users’ needs). Unlike many

software vendors, if a new company puts up a competitive

site that customers perceive to have higher quality, cus-

tomers will almost immediately shift their business to the

new site. Thus, it is often advantageous to be “later than

and better” instead of “sooner but worse.” Although the

idea of “sticky Web sites” has been discussed and mech-

anisms to encourage customers to come back have been

developed (Menasc ́e, 2000), thus far the key mechanism

to bring repeat customers to Web sites is high quality. It

seems likely that this will continue to be true for the fore-

seeable future.

In software development, a process-driver is a factor

that has a strong influence on the process used to develop

the software. Thus, if software is required to have high

reliability, the development process must be adapted to

ensure that the software works well. When I have sur-

veyed the important quality process drivers for tradi-

tional software, developers always give a single answer

that stands alone far above the rest: time-to-market. But

when I recently made the same survey of Web software

development managers and practitioners, they claim that

time-to-market, although still important, is no longer the

dominant process driver. Instead, the three most impor-

tant quality criteria for success of Web applications (and

thus, the underlying software) were given as

Reliability

Usability

Security

An additional four important criteria that were listed are

Availability

Scalability

Maintainability

Performance

Of course, it would be foolish to claim that this is a

complete list of important or even relevant quality at-

tributes. Quality attributes such as customer service, qual-

ity of products, price, and delivery are also important but

not related to the software and thus beyond the scope

of this chapter. Nevertheless, these quality attributes

track closely with what is said in other books and arti-

cles (Constantine & Lockwood, 2000; Dustin, Rashka, &

McDarmid, 2001; Kassem et al., 2000; Murugesan & Desh-

pande, 2001; Powell, 1998; Scharl, 2000). Thus, there is

wide agreement that satisfying quality attributes is essen-

tial to Web software, and these seven provide a solid basis

for evaluating Web software. These quality attributes are

used as a basis for suggesting specific ways to engineer

Web site software, using the available technologies.

Before proceeding with the technology aspects of this

chapter, let’s explore the reasons these quality attributes

are so important. These quality factors will have a much

stronger impact on the profits of Web-based companies

than for most traditional software. The reasons for the

first three quality requirements—reliability, usability, and

security—may become obvious by analyzing some of the

new uses of this software. The most obvious is that of

direct selling to customers, that is, “B2C.” This includes

companies that sell books and other small items such as

Amazon, plane tickets such as Yahoo and Expedia, and

rental companies such as Netflix. Customers who buy

books from a Web site expect the same quality of service

that they would get from going to a bookstore at the mall,

but without the overhead of actually driving to the mall.

We expect to be able to find the books we want in a con-

venient way (usability), we expect to be able to make the

purchase without difficulty (usability), we expect the cor-

rect books to arrive at our house in the specified number

of days (reliability), and we expect the correct amount to

be billed to our credit card (reliability).

The issue of security of Web applications is getting

more important. One of the major concerns of security for

e-business, of course, has to do with security of data. Cus-

tomers expect their credit card and personal information

to be held in confidence. Identity theft, where a criminal

takes the entire credit history and assumes the name of

another person, is becoming more common and can be

done by taking advantage holes in Web software. The se-

curity also works in the opposite direction. Improper use

of cookies has opened up holes for users. One example is

that of Web software storing price information in a cookie

on the client-side, which allowed customers to change the

price of items they bought on the Web. As a field, we are

continuing to evolve our expectations of security and our

ability to support security.

The additional quality requirements are less obvious.

Whereas a bookstore on the corner (“brick and mor-

tar”) might expect to have customers form the neighbor-

hood Monday through Saturday, 8:00 a.m. to 7:00 p.m., a

Web-based company can expect customers from all over

the world. It might be 3:00 in the morning in Virginia,

but it’s the middle of the afternoon in Beijing! It might

be Thanksgiving holiday in the United States, but it’s

just another spring day in South Africa. Thus, Web sites

must have extremely high availability, not just 24/7, but

24/7/365.