Chapter4 - 4 Approaches to reusability “Follow the lead...

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4 Approaches to reusability F ollow the lead of hardware design ! It is not right that every new development should start from scratch . There should be catalogs of software modules , as there are catalogs of VLSI devices : when we build a new system , we should be ordering components from these catalogs and combining them , rather than reinventing the wheel every time . We would write less software , and perhaps do a better job at that which we do get to write . Wouldn’t then some of the problems that everybody complains about — the high costs , the overruns , the lack of reliability — just go away ? Why is it not so ? You have probably heard remarks of this kind; perhaps you have uttered them yourself. As early as 1968, at the now famous NATO conference on software engineering, Doug McIlroy was advocating “ mass-produced software components ”. Reusability, as a dream, is not new. It would be absurd to deny that some reuse occurs in software development. In fact one of the most impressive developments in the industry since the first edition of this book was published in 1988 has been the gradual emergence of reusable components, often modest individually but regularly gaining ground; they range from small modules meant to work with Microsoft’s Visual Basic (VBX) and OLE 2 (OCX, now ActiveX) to full libraries, also known as “frameworks”, for object-oriented environments. Another exciting development is the growth of the Internet: the advent of a wired society has eased or in some cases removed some of the logistic obstacles to reuse which, only a few years ago, might have appeared almost insurmountable. But this is only a beginning. We are far from McIlroy’s vision of turning software development into a component-based industry. The techniques of object-oriented software construction make it possible for the first time to envision a state of the discipline, in the not too distant future, in which this vision will have become the reality, for the greatest benefit not just of software developers but, more importantly, of those who need their products — quickly, and at a high level of quality. In this chapter we will explore some of the issues that must be addressed for reusability to succeed on such a large scale. The resulting concepts will guide the discussion of object-oriented techniques throughout the rest of this book.
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APPROACHES TO REUSABILITY § 4.1 68 4.1 THE GOALS OF REUSABILITY We should first understand why it is so important to improve software reusability. No need here for “motherhood and apple pie” arguments: as we will see, the most commonly touted benefits are not necessarily the most significant; by going beyond the obvious we can make sure that our quest for reuse will pursue the right targets, avoid mirages, and yield the highest return on our investment.
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This note was uploaded on 10/02/2009 for the course CS 4376 taught by Professor Christeansan during the Spring '09 term at Dallas Colleges.

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Chapter4 - 4 Approaches to reusability “Follow the lead...

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