Steve McConnell Text Banner

 

 

ieeesoft-small.gif (2738 bytes)


From the Editor
IEEE Software, January/February 2001

Who Needs Software Engineering?

The traditional distinction between software and hardware was that software was easily changeable and therefore "soft," whereas hardware was captured on a physical medium like a chip, was hard to change, and was therefore "hard." This traditional distinction seems to be breaking down today. Software delivered via the internet is clearly "soft" in the traditional sense, but software delivered via CD or DVD is hardly "soft" in the sense of being "easy to change."

We now commonly see software being delivered on EPROMs; the Electronic Control Module that controls my car’s fuel injection is an example. I can take my car to my dealer to have the chip reprogrammed, so in some sense the program on the chip is soft, but is it software? Should the chip developers be using software engineering?

Computer chip designers are now doing much of their chip development using software-engineering-like tools. Only at the last minute is the code committed to silicon. Do we really think that committing code to a CD ROM makes it software but committing it to a silicon wafer makes it hardware? Have we arrived at a point where even computer hardware is really software?

If software and hardware are totally different, then electrical engineers designing computer chips don’t need to know about software engineering. But if modern chip design involves a significant amount of programming, then perhaps electrical engineers should know something about software engineering. Should computer hardware be designed using software engineering?

Throw a few other disciplines into the mix such as web programming and games development, and I think there is a fundamental question lurking here: What is Software? This question is important because it leads into a second question, What is software engineering today, and who needs it?

Wolfgang Strigel: There is no doubt that the distinction between software and hardware has become blurred. When the term software was coined, there was a clearer distinction, or nobody cared because it sounded good and made intuitive sense. I don’t think either that it is important that software is modifiable (or "soft" once it is completed). Software does not change its nature by being turned into something "hard" or unmodifiable. After all we have accepted the concept of selling software on CDs. And RAM can also be write-protected. What matters is whether there is a "program" that can be executed by a device.

The project plan for building a high-rise is a set of complex instructions, decision points and so on that could be interpreted as a software program. But it is not executed by a device. But how about multimedia, say an animated movie? It has instructions for movement, rendering, etc. and is executed by a device. It also can be modified. How about a set of MIDI instructions that produce music if delivered to an electronic instrument? This is not fundamentally different from a ladder diagram which controls the execution of a Programmable Logic Controller.

Larry Graham: I agree that the line between software and hardware is blurry. Patent law has a fairly rich tradition that equates the two—virtually every hardware device can be described in terms of a function it performs, and vice versa.

Annie Combelles: I think the basic practices needed to develop software properly are always the same: get clear and complete requirements from customers; manage changes to requirements; estimate, plan and track the work to be done; select an adequate life cycle; define and perform QA activities; and maintain product integrity. The software architecture and coding might be different from one application to the other, but the process aspects are invariant.

Tomoo Matsubara: I don’t think software development is always the same. My recommendation for improving software process is to apply domain-specific methodologies and tools and conduct problem focused process improvement. The levels of importance and priorities are different between domains.

For example, one of most critical process for commercial software is fixing data flow. For scientific software, a key to success is choosing right algorithm. For COTS, it’s designing a good man/machine interface. For embedded systems, it’s pushing instructions into the fewest memory chips. For maintenance, it’s rigorous testing with regression tests. Software development practices should vary accordingly.

Grant Rule: Think about the games industry, where the "software" is delivered on CD ROM or game cartridges. Game development can take vast amounts of schedule. Teams can be quite large—25-30 people from a variety of disciplines including analysts, designers, coders, testers, QA staff, and project management—and lots of non-traditional software personnel such as writers, artists, and so on. Schedules have to be managed carefully to meet holiday sales seasons. If a game misses the marketing window and may be a commercial failure; there’s no second chance. Reliability is important; the game is mass-produced on CD-ROM, and from that point forward, there is no real chance to correct it—it is infeasible to recall hundreds of thousands of copies to fix a defect.

The result seems to be that, in some cases at least, games developers take a more rigorous approach to "engineering" their software than do some developers of commercial data processing applications. All this seems to be "software engineering" to me.

Robert Cochran: I use the following definition to describe what is unique or special about software:

(1) Software is intangible (which I think is true even if it gets embedded).

(2) It has high intellectual content (many other intangibles have low intellectual content).

(3) It is generally not recognized as an asset by accountants and so is off balance sheet.

(4) Its development process is labor intensive and is team and project based. We forget sometimes how little of the rest of the world regards projects as the normal way to work.

(5) Software doesn’t exhibit any real separation between R&D and production.

(6) Software is potentially infinitely changeable. Once you make a physical widget, there are severe limits on how you can change it. In principle we can keep changing software for ever.

Is there any real distinction between printing out a source code listing, creating a binary, burning software onto a chip or a CD ROM? If all these cases we are just "fixing" a copy of the software in some form which cannot directly or easily be modified. That does not have any relevance to the nature of the software as such.

Grant Rule: That makes software just like any written work or other art—books, design drawings, and so on. The media/technology may be different such as wax tablets, canvas, or paper, but anything that can have multiple copies made in a mutable medium sounds like it "could" be this thing called "software’.

Martin Fowler: Robert’s Number 5 seems to be the key point. Until you deploy you can build, modify, and evolve the software, regardless of whether you eventually deploy to PROMs or CD. That ability to evolve while building is a key aspect of software that has no equivalent in disciplines where you must separate design from construction.

This question of how "soft" is software is quite an important point and one that gels particularly with me. One of the reasons that I’m so much in favor of light methods is that they try to make software softer while many methodologies try to make it harder. In the IS world softness is an important and valuable asset.

Steve McConnell: That does seem to be the age-old challenge—how do you keep software from becoming brittle? How do you keep it soft? Whether you’re creating software, or a computer chip, or even a building, it seems as though it would be advantageous to keep the thing you’re building "soft" as far as possible into the project.

Terry Bollinger: This overall question helps to deal with trying to understand the baffling diversity of production styles in the software marketplace. "Hard" software such as that found in Intel processor chips is catastrophically expensive to fix after fielding, and so drives the entire software design process to be very, very conservative and validation intensive. "Fluid" software that can be changed automatically over the Internet drives the opposite behavior. I think that understanding these kinds of issues is quite fundamental to software management.

I do think we need to have a better overall definition of software. The very fact that I had to mangle together a phrase as awful as "hard" software to describe algorithms encoded into silicon shows that the industry has become more complex than it was in the days when you had vacuum tubes and bits on punched cards, and not much in between.

I think the distinction needs to focus on the idea of "information machines"—what we have traditionally called software—versus the particular method of distribution and update of such machines. Those are two separate dimensions, not one. A bunch of gears is not an information machine, because it relies primarily on physical materials for its properties, even if it happens to do a little information processing at the same time (for example, odometers in cars). A structured algorithm masked into an addressable array that is an integral part of a processor chip most emphatically is an information machine, because its complete set of properties can be represented as structured binary information only, without any reference to the physical properties of the chip.

Don Bagert: In defining what’s really software, my thought is to look at what the object code does (rather than where it resides), as well as the source code. I would define it as follows: "Software is a set of instructions which are interpreted or executed by a computer." The source code is definitely "soft" not in the sense of the deployment media but in that it is a non-physical entity. It consists of a series of instructions, which are by definition non-physical, which can be translated into object code or interpreted by a computer processor. My colleague Dan Cooke has an interesting view: a Turing machine corresponds to computer hardware, while an individual Turing machine defined to solve a particular problem corresponds to software.

Steve McConnell: My original focus on the media on which the software happens to be deployed seems to have been a red herring. I think software engineering applies broadly to creating complex "instructions," regardless of the target media. Years ago, people argued that the need for software engineering had passed because Fortran had been invented. People didn’t have to write programs anymore—they could just write down formulas! Thirty years later we now think of Fortran programming as comparatively low level software engineering—"writing down formulas" is harder than it looks.

As the years go by, we see the same argument repeated time and time again. The early claims about creating programs using Visual Basic were reminiscent of the early press on Fortran—"no more writing code—just drag and drop buttons and dialogs!" And today more new programs are being written in Visual Basic than any other language. Ten years from now we’ll probably see programming environments that are much higher level than Visual Basic; people working in those environments will benefit from software engineering.

Martin Fowler: This is an important point. Often we see people talk about things "without programming" (one of my alarm bell phrases). You find this in phrases like, "you buy our ERP system and you can customize it for your business without programming." So you end up with people who are experts in customizing XYZ’s ERP system. Are they doing software engineering? I would say yes, even though their language is putting configuration information into tables. They still need to know about debugging and testing.

Indeed whenever we talk about writing tools so that "the users can configure the software without programming" we run into the same problems. If you can enter programs through wizards, you still have to be able to debug and test the results.

Wolfgang Strigel: At the risk of being simplistic I would define software as follows: "Software is a set of instructions which are interpreted (or executed) by a computer." I did not say "electronic computer" since it could well be a chemical computer or one that operates with light. That delegates the problem to defining the term "computer"—and that’s a hardware problem!


Editor: Steve McConnell, Construx Software, 14715 Bel-Red Road, #100, Bellevue, WA 98007.
E-mail: stevemcc@construx.com - WWW: http://www.construx.com/stevemcc/

Email me at stevemcc@construx.com.