I think most people are likely to take the question to refer to a consumer product like Word or Windows 7. In this case, the product primarily consists of an executable module but no source code. In addition, to make it fit for its intended use, there are several other assumed artifacts associated or imbedded into the product. One is either an installer application or instructions on how the product is to be placed into the intended environment. In addition, there is an implied deliverable which will instruct the end-user how to perform the tasks for which the product intended using the product. These days that is often left implied more than explicit as many products are designed to be self-evident. This means that the intended end-user has sufficient experience with similar user interfaces that the use can be learned with some exploration and no explicit training. Of course this is not always the case and products may either embed the user manual into the product or provide it as a separate artifact.
There is another sense of software product though. If you consider the automobile factory that turns out cars, the cars are products to be sold to consumers. However the factory itself is an asset that can be sold to another auto maker and retooled for their use. In a similar way, source code is a major component in a product that allows a software vendor to create software products. This "software factory" is a tangible asset and is recognized as that through intellectual property laws and common sense. (To avoid some awkward language, from here on, when I refer to a software product, I am using this second sense of the term and will ignore products that only include executables. )But is the source code the entire asset? If we were to sell our intellectual property to another, what can reasonably be considered part of the asset?
In the rush to market, many software vendors are willing to sacrifice the quality of the allied artifacts of the complete system. While this helps to achieve the end goal of creating a working system, it creates technical debt in the deferred maintenance on the artifact with a measurable increase in cost to the total cost of ownership. If the product will never be modified, the complete lack of supporting documentation for the product is reasonable. Even if some was produced during the initial construction of the product, there is no reason to keep it since it will never be read. But how many software products are created that are never intended to be modified? The correction of latent defects, changes in the environment, new requirements, are just a few of the many reasons why the maintenance phase of a software product life cycle is typically the costliest. To ignore the needs of this phase of the product life-cycle are foolish and self-defeating. Therefore any technical debt incurred from the initial development will eventually need to be paid if the consequences of that debt are to be avoided.
The platonic ideal that is sought is some form of self-documenting code. While local comments, when done well, or even well written code without comments, can often be understood without additional commentary, large software systems cannot be self-documenting since many issues transcend individual modules. A software engineer may be able to reproduce the information needed from the source code alone, or at least find a way to insert the modification without it, but this is most likely a more expensive fix than it would have been had the recreation work not been needed. The lack of adequate support for the code base increases maintenance cost. Further, until a code base automatically includes self-documenting ways to explain design choices that transcend individual module, this kind of documentation will continue to exist outside of the source code itself.
This highlights a weakness in the current practice of software engineering management. The true value of this artifact is discounted by management. Since the increased support cost can never be quantified, there is no self-correction of management attitudes. The continued ratio of maintenance cost to total life-cycle cost will remain the same. Worse, there are two compounding effects from this. First, the best information about the design of the system often only exists in the minds of the developers. When they leave the project, it is usually lost for good. Even if they remain in the same organization, the fidelity of the information is lost over time. Second, without an adequate understanding of the design principles used in constructing the product, a maintainer is likely to undermine some of the design clarity that requires restraint on the part of the coder due to ignorance. It is as if the architect leaves no plans for a building behind and the maintenance engineer tries to knock out a wall only to discover an unexpected support post or beam. Even worse would be to not recognize the structural nature of the element during the remodeling and remove it, thus weakening the structure increasing the risk of structural failure.
(originally posted at Dale's Dilettantic Deliberations Aug 12, 2011)
As Agile methods gain wider use in industry, some inexperienced developers are likely to believe that producing good design documentation is just a bother. A lack of professional development, the desire to just get on with their career, an ignorance of how to best document the design, or some combination of all three likely contributes to the poor quality of this product artifact. Often professionals do not even consider the design artifact to be part of the product itself but view it as some form of construction artifact that serves no purpose after delivery. Certainly many management teams do not appreciate, nor know how to evaluate, the quality of these allied artifacts.
The lack of attention given to the maintenance phase infrastructure and staff needs is a significant blind spot. It has always been a function that has suffered from lower status than the initial construction. As the product life cycles of these software products has gotten longer, there is likely to be at least some far sighted management teams who will eventually realize that long-term profits can be improved through a reduced maintenance phase in their software assets. Once that begins to happen, the types of design documents that most efficiently support the maintenance needs will become the object of study. Until then, these support staffs will continue to be expected to do their jobs with less than ideal knowledge transfer and the need to continually read the minds of developers who are no longer around to ask.
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