Document 190307

Omnext white paper, March 2010
How to save on software maintenance costs
Abstract
The cost of software maintenance is rising dramatically and it has been estimated in [1] that
nowadays software maintenance accounts for more than 90% of the total cost of software,
whereas it was around 50% a couple of decades ago. There are several reasons for this. We
can see that software systems become hard to maintain over time, while every day more and
more software is being produced.
Documentation is lacking or incomplete and the people who know the software leave or
retire without being replaced. Furthermore, systems tend to become increasingly complex.
This makes extending a system difficult and costly. Rebuilding a system is usually not an
option because the system that needs to be replaced is large, the test coverage unknown and
the original and modified requirements are not well documented.
100% = Total cost of software
100%
Maintenance costs
50%
1970
2009
Figure 1: Development of Software maintenance costs as percentage of total cost
Given the enormous costs and efforts involved in software maintenance, every company
should consider ways to make savings here, as also observed in [15]. This paper presents
several known ways to save on software maintenance costs, and it also presents an
integrated approach developed by Omnext.
Page 1 of 12
Introduction and cost drivers
Several best practices for the process optimization of software maintenance activities can be
applied, such as CMMI [10], ITIL [23] and ASL/BISL [12]. All of these focus on the
optimization of processes. What is at least as interesting, however, is where the real costs of
software maintenance lie. Until recently [2, slide 6, 2002 and 6, 2008] relatively little was
known about the software maintenance process and the factors that influence the cost of it.
An investigation of recent reports about the costs of software maintenance has uncovered
the following.
The costs of understanding
Maintenance consists of a number of different activities, as shown in figure 2. One of the key
issues that needs to be dealt with is limited understanding. Limited understanding refers to
how quickly a software engineer can understand where to make a change or correction in
software. Some 40-60% of the maintenance effort is devoted to this task, as is noted in the
Guide to the Software Engineering Body of Knowledge (SWEBOK) [3].Thus, the topic of
software comprehension is of great interest to the software world.
Figure 2: Analyzing is almost 50% of the total maintenance effort
The costs of ‘lack of’ or ‘little’ documentation
One way to remedy limited understanding is to produce documentation and other
supporting descriptions such as data- or UML-models. However, how much documentation
is enough? This topic was investigated during the twenty-third annual international
conference on the design of communication [13, 2005], which reached the following
conclusion: The surveys confirmed that source code and comments are the most important
artifacts for understanding a system to be maintained.
Data model and requirement description were other important artifacts. Surprisingly, and
contrary to what we found in the literature, architectural models and other general views of
the system were not found to be very important.
How to save on software maintenance costs
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The two central costs of a developer’s effort
In [6] it is argued that software engineering practices can be improved if they address factors
that have been shown empirically to affect a developer’s effort during software evolution.
The two central finding were that:
1. The volatility of requirements had a large and consistently negative effect on effort.
2. The dispersion of changed code (distribution over different files/components) also had a
large and consistently negative effect on change effort. Typically, the change requests
were described by referencing a user scenario, i.e. a sequence of interactions between
the user and the system, and by requesting a change to that scenario. The developers
expressed that considerable time was spent understanding relevant, intermediate code
when it was dispersed over many files. In other words, the qualitative data shows that
when code involved in the changed user scenario was dispersed over many components
that user scenario was difficult to change.
Other costs involved
Other cost factors in software maintenance are, among others, lack of programming
standards and guidelines, solving bugs and problems, implementing changes, testing, impact
analysis and integration with other systems. Any speedup in these areas would help reduce
costs.
The above explains what is known about the aspects that influence the costs of operational
software maintenance. The next sections will be a summary of some of the practical cost
savings possibilities presented in the literature.
Six ways to save
(Re)documentation
Most existing systems are often poorly documented [5, 9]. Below we refer to several case
studies where money could be saved by (re)documentation.
•
In one of the few controlled experiments relating to this topic, research [5] has shown
that the programmers who had no documentation spent 21.5% longer understanding
the code. Knowing that understanding may take around 50% of the total costs of
software maintenance, we could save 12% of the total cost of software maintenance if
we had documentation in place. Another particularly interesting result was that, without
documentation, differences in skill levels between good and bad programmers
disappeared. With documentation, good programmers did better work than poor
programmers did. Without documentation, they both did equally bad work.
Consequently, spending money on the best people is a waste without documentation.
How to save on software maintenance costs
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•
Other gains of (re)documentation are reported in [18] where the break-even point
occurred after 1.5 years of effort, which means that the extra investment in
(re)documentation started paying off after 1.5 years of (re)documentation activity.
•
In [6] and also quoted in our introduction, it is said that the need to understand
dispersed code is one of the two main cost factors of software maintenance, so having
documentation of the dispersed code along a user scenario would significantly help.
Eliminating dead code
It is reported [16, 17] that up to 30% of the software in an older system can be dead code. By
eliminating dead code, we reduce the code size. For an introduction to eliminating dead
code and why it is important, we refer to [16]:
Dead code
Dead code means unnecessary, inoperative code that can be removed without affecting the
program functionality.
Dead code includes functions and sub-programs that are never called, properties that are
never read or written, and constants and enums that are never referenced. Variables should
be both read and written to. User-defined types can also be dead and a project may contain
redundant API declarations. Even entire modules and classes can be completely redundant.
The opposite of dead code is live, operational code. There are also several types of semi-dead
code, that is, live-looking code and controls that are not actually required at run-time.
Below we present several reasons for why we should care about dead code.
•
Dead code is a very common phenomenon. It can account for 30-40% of a project's size
and increase the EXE or DLL file size by hundreds of kilobytes. The average amount of
dead code is 15%. The more developers there are, the tighter the deadlines, the older
and larger the system, the more dead code there is.
•
Dead code means excessive memory use and slower execution. It also means more code
to read and maintain. It leads to higher costs, especially during maintenance. If the code
is present, programmers must spend time understanding it.
•
Leaving dead code in a completed project means carrying around untested code and
hidden bugs. Dead code may inadvertently become operative later, meaning a possible
source for errors.
•
If you are considering the purchase of someone's source, make sure that you are not
paying for hundreds of thousands of unnecessary lines. If you just took on a new project,
the first thing to do should be to remove any significant dead parts. If you are finishing
your newest release, remove the dead bits to ease future maintenance efforts.
As reported in [19], the savings can be significant. It will cost at least $1.00 per source line
per year to maintain application software. Costs for the maintenance of both dead code as
well as active code are therefore estimated to be at least $1.00 per source line.
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Eliminating cloned code
When applying new functionality, many programmers cannot resist the temptation to copy
(clone) and customize existing pieces of code. The problem with this approach is that bugs
are copied as well and future modifications may have to be applied to each clone, which is
an error-prone procedure. Large software systems typically contain 10-25% of such cloned
code. This introduces extra maintenance costs above the standard $1.00 per source line. The
number of clones can be reduced by isolating the clone code in a (possibly parameterized)
subprogram.
It is reported in [19] that considerable savings on maintenance can be achieved by keeping
the amount of cloned code to a minimum. We quote them below.
Cloned code
Large software systems typically contain 10-25% redundant code. This redundancy is caused
by the common programming practice of replicating (or cloning) existing code and then
customizing to handle new demands on an application. An IT organization consequently
spends corresponding amounts of its budget redundantly maintaining this code; a bug in one
code fragment is also a bug in all of its hidden clones.
If redundant code were removed, the IT organization could spend the budget savings on
solving new problems, enhancing the efficiency of the parent organization. The savings can
be significant, because it typically costs, as stated earlier in reference to dead code
elimination, at least $1.00 per source line per year to keep application software in running
order.
Avoiding and eliminating bugs
Avoiding and eliminating bugs are on the rise. The following is noted in [20].
Bugs
Bugs in software are costly and difficult to find and fix. In recent years, many tools (like
Bandera, ESC/Java2, FindBugs, JLint, and PMD) and techniques have been developed for
automatically finding bugs by analyzing source code or intermediate code statically (at
compile time). These tools look for bug patterns which are code idioms that are often errors
or potential problems. Sometimes these patterns are covered by local Standards and
Guidelines or programming rules. An example is an empty catch block. In code with an empty
catch block an exception is caught, but nothing is done. In most circumstances, this swallows
an exception which should either be acted on or reported. Another example is an empty if
statement. In an empty if statement a condition is checked but nothing is done about it.
Either remove them or act upon them.
In [20], Hovemeyer and Pugh relate their experiences of applying bug pattern detectors to
programs. They have drawn several interesting conclusions about why you should apply
them.
How to save on software maintenance costs
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…..“First, we have found that even well tested code written by experts contains a surprising
number of obvious bugs. Second, Java (and similar languages) has many language features
and APIs which are prone to misuse. Third, we found that simple automatic techniques can
be effective at countering the impact of both ordinary mistakes and misunderstood language
features.”….
The above experience combined with the rule of thumb often adhered to that fixing one bug
costs about $1.000 makes preventing or eliminating bugs an attractive option.
Focused test activities
In [21], regression testing techniques are discussed and classified. The authors point out that
the “retest all method” is a conventional method for regression testing, in which all the tests
in the existing test suite are rerun.
This “retest all” technique has proven very expensive compared with other techniques they
discuss. At the heart of these techniques lies the observation that unmodified parts of
programs need less test attention. So only focusing on modified parts leads to less
regression test time and therefore substantial cost savings.
In general: Reducing complexity leads to improved maintainability
In [4] it is argued that considerable savings can be achieved by monitoring and improving the
technical quality of a system before and during maintenance. This is also confirmed in [22],
where the following conclusion is drawn: On the basis of software maintenance projects in a
commercial application environment, it was confirmed that software maintenance costs are
significantly affected by the levels of existing software complexity. The analysis on this site
suggests that high levels of software complexity account for approximately 25%
maintenance costs or more than 17% of total life-cycle costs. Given the extremely high cost
of maintenance in commercial applications, the neglect of software complexity is potentially
a serious omission.
An integrated approach
Thus far we have seen six possible ways to save costs and improve quality. What we are
looking for is a practical integrated approach to identify these possible ways and apply them.
During the past decade, Omnext has developed CARE, a concept that offers an integrated
and systematic approach to cost reductions. CARE stands for Computer Aided
(Re)documentation & Evaluation. At the heart of this concept lies the idea of continuous
incremental improvement [much like the Kaizen [8] principle]. CARE allows you to generate
savings of up to 50% on the costs of, among others, impact analysis, testing, and
documenting. Furthermore, it enables you to improve the quality of your software.
How to save on software maintenance costs
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The concept comprises the computer-aided construction of technical and functional
documentation (in the case of Omnext, this is realized through the use of its own proprietary
developed technology Source2VALUE*). The concept also encompasses the automated
monitoring of a software system’s quality and size. Suggestions for improvement will be
made on the results that are found, suggestions for improvement will be proposed. CARE
can be tailored to situation in which it is used.
Figure 3: CARE
(* Source2VALUE™ is a flexible technology environment that allows you to document and
evaluate your systems periodically. This is done by automatically analyzing the source code,
workflow definitions, menu structures, and batch-job definitions.)
How to save on software maintenance costs
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•
Intake: A CARE environment is defined depending on the domain for which you wish to have
a software documentation and software evaluation environment. The result, the CARE
definition, is a clear specification of the application software sources to be analyzed, the
standards, and the method of documentation and evaluation.
•
Monitor: Monitoring based on the CARE definition in order to analyze the application
sources automatically and periodically. The result is a repository with quality and size
measurements. For documentation purposes, this repository also contains all the structures
and relationships of and between the application sources. The result is a data warehouse
containing all the application sources and characteristics
•
Report: A variety of reports can be generated from the object in the repository. These may
contain information about quality, size, and trend development. The technical
documentation is also generated. In addition, the functional documentation that may need
to be adapted is identified from the changes in the application.
•
Analyze: Analysis is carried out by looking at signals, quality, and productivity KPIs, and then
turning the results into recommendations for improvement. The functional documentation is
also analyzed from the signals.
•
Improve: Improvement occurs by implementing the improvement recommendations and
updating the functional documentation. This updating is carried out manually or is
automatically supported by tooling. If required, the CARE definition can be updated on the
basis of advanced insight.
We illustrate below how the ‘six ways to save’ from above can reduce maintenance costs.
Source2VALUE™
Omnext’s Source2VALUE product supports (re)documentation by automatically generating
technical documentation and semi-automatically generating functional documentation
through the Use Case Editor (UCE). The UCE enables you to reproduce the functional
working of an implemented application at a fast speed. The UCE can be deployed repeatedly,
so you can guarantee that functional changes reflect the actual current source code.
In summary, it provides the following functionality:
•
Use Case Recovery: This allows you to reproduce the functional operation of your
application quickly from the source code
•
Business Rule Harvesting: This allows you to distill the business rules from your source
code
•
Update signaling: This signals, on the basis of changes of source code, where you need to
update your functional documentation
In addition, Source2VALUE also provides insight into the quality, size, and functioning of the
analyzed application. This relates to, among others, source code, workflow definitions, menu
structures, and batch-job definitions. This way you are given an insight into:
How to save on software maintenance costs
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•
•
•
•
•
•
•
the metrics for software quality and size
the trend of the metrics for software quality and size
the structure and functioning of the application
the application source code (dead and cloned code)
the relationships between the different application components
the system workflow
specification of differences in different application versions
Business Benefits
In the “Six ways to save” section, we presented possible savings from the literature. After
applying one or more improvements, the maintenance costs will decrease, as shown in
Figure 4. Note that the actual maintenance costs vary from system to system. In this case,
three trend lines for the development of software maintenance costs over time are given.
Software
Maintenance costs
CARE
Time
Figure 4: Effect of CARE
If you are wondering what the real savings could be, Table 1 below shows a combination of
possible savings, as reported in the literature. In this case, a hypothetical system of one
million lines of code, with average maintenance costs of one dollar per line of code per year
[19] has been chosen.
Ways to save
(Re)documentation
Dead code
Cloned code
Literature source
[5]
[16]
[19]
Avoiding bugs
General complexity
10 avoided bugs,
General experience
$500-$1000 per bug fix
[22]
up to 25%
Table 1: Mentioned savings in literature
How to save on software maintenance costs
Savings in literature
10 - 25%
30 - 40%
10 - 25%
Possible savings
$100.000-$250.000
$300.000-$400.000
$100.000-$250.000
$5.000-$10.000
$250.000
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Note that in reality the overall possible savings will most likely be lower. However, if you
suppose that even the saving possibilities that we have mentioned result in an overall
scenario where savings are 30% ($300.000), then you would achieve a substantial benefit in
terms of costs, not to mention the positive overall effects on quality and productivity for all
maintenance efforts.
Summary
We have presented six ways from the literature to save software maintenance costs. These
are often based on empirical studies. We then described the Omnext CARE concept, a
practical solution for establishing continuous incremental improvement and thus lowering
software maintenance costs. Furthermore, we described the unique state-of-the-art
capabilities of Omnext’s Source2VALUE technology. Finally, using an integrated approach,
we presented the financial benefits for your business, which, as we have seen, can be
substantial.
Call to action
After reading this paper one thing should be clear. Saving on maintenance costs will never
be achieved with one major action. It calls for an integrated approach, preferably
institutionalized in the company’s own software maintenance area. Practical information on
software system(s) combined with the right supportive technology and the right approach
(where relevant aspects get their attention) is needed. Only then can software maintenance
costs be lowered and kept low in a sustainable way.
Authors
Ir. Floris P. Engelbertink, Omnext, e-mail: [email protected]
Dr. Harald H. Vogt, Omnext, e-mail: [email protected]
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