Software Size is the single biggest determinant of effort or cost on a software project.
Consistent software sizing can help all aspects of software portfolio management
Software estimation and specifically agile software estimation is thought to be difficult and is certainly notoriously unreliable. Yet having reliable estimates is essential for sound investment decisions and effective planning.
Estimating software size (and subsequently cost and schedule) is important to give managers an understanding of how much it will cost and how long it will take. Managers and executives are constantly faced with difficult decisions about software work. On larger projects, budgets and schedules are frequently exceeded, both of which lead to considerable waste and inefficiencies. Managers need to know the likely cost and duration to develop software so that they can plan accordingly. They are expected to make dependable decisions about priority and staff allocation and yet often do so without reliable software estimation of the time and effort needed.
Most software professionals believe that it is impossible to estimate software development work, or that it is very time consuming. This is not so.
Why are developer estimates unreliable?
Developers often resist offering estimates, sometimes because they fear that their estimates may be treated as commitments. Also they resist too much detailed sizing analysis up front in case the requirements are not implemented. Estimation in story points (using planning poker) is a common practice in Agile teams. But in spite of its popularity, it is a flawed approach and can often be out by orders of magnitude. Story points are a helpful means of communicating within the team about how hard something might be to do. But that’s all! They are easily manipulated, gameable, inconsistent and for most purposes, meaningless.
It is Natural to Underestimate
Developers almost always underestimate the time and effort actually required to get software delivered. It is human nature to do so. They only consider the factors that they know about, and yet with software, there are often unknowns that cause delay, theses are rarely allowed for in technical estimation. Moreover developers’ initial proposals are usually low in order to “win the work”.
The Software Industry Must do Better
Poor estimation is one of the root causes of large project failures. It is incumbent on the industry to get better at software (effort, cost and duration) estimation. With more reliable early estimates of software work, better decisions can be made earlier and wasteful delays avoided.
How to Estimate Software Work, Reliably?
As many as 60 factors can affect the time and effort to develop software (such as complexity, work environment, executive support, technical experience, requirements volatility). The single most significant factor is size, specifically functional size. (put your story points to one side just for now, as they are not a measure of size but a pseudo effort guess).
Reliable Software Sizing is Possible – and it’s not so hard either.
Estimate Software Functional Size First
Once you know the functional size, you can quickly derive valid estimates for other dimensions, such as:
- staff needed
- costs
- time to develop
- tests needed to achieve suitable quality
- and many more
What is Functional Size?
Functional size arises from Functional Size Measurement (FSM). It is a mature and proven standardised technique for software sizing. It is a formal engineering practice approved by the ISO standards groups. It is agnostic of the technology and development methodology. Functional size is a universal measure that applies to all types of software. It is considered from the users perspective. It is objective and valid, and consistent. Two people measuring the functional size should come up with the same number each time. The unit of measure is the function point, specifically the COSMIC function point or CFP. The CFP can be estimated or counted (exactly) just from requirements and specifications. The functional size is independent of the coding language used to develop it. FSM has been around for many years and has proven to be the most reliable measure of software size. FSM allows you to estimate or measure size before, during and after the code has been written.
Can I learn to estimate software size quickly?
Yes, you can learn to size software (properly using a functional sizing standard) in a couple of days or less. You can become fully proficient and certified in just a few weeks. It may take longer to learn how to leverage the value of the measurement, but for that, there are experienced advisors. ScopeMaster does the heavy lifting here, so using ScopeMaster will accelerate your learning and software estimation!
Can I automate software estimation?
Yes. ScopeMaster is the first and only tool to reliably estimate functional size directly and automatically from written requirements. Don’t just take our word for it though. Experts and academics around the world agree that ScopeMaster® is a breakthrough automated sizing tool: Academic validation of ScopeMaster as an automated sizing tool.
Bring certainty to your software work with automated functional size measurement.
For more on COSMIC functional size measurement, visit https://www.cosmic-sizing.org
The great thing about knowing the size before coding, is that you can allocate the correct amount of time and funds to get the job done. Just by knowing the size, you can usually save 10% or more on a larger software project, sometimes even more.
If you want to get started with effective and rapid software estimation, use ScopeMaster to estimate the COSMIC function points directly and instantly from your requirements or user stories.
Automated Software Estimation with ScopeMaster
ScopeMaster was conceived as a tool to automate the clerical work of measuring the functional size of software from requirements. “The reason I set out to write a tool to do this is because, as a software project manager, I found that functional size is the single most significant factor that I need in order to manage a project successfully.” Colin Hammond, Founder.
ScopeMaster interprets the functional intent of the user story or software requirement, and so is able to automate functional sizing, which can then be used for further estimation of software development.
Not only is ScopeMaster much faster than measuring manually (at least 4 times faster), it costs substantially less than manual sizing, certified counters are scarce and ScopeMaster takes much of the drudgery out of doing the job. ScopeMaster “reads” the requirements, interprets the functional intent and then sizes them accordingly. It can estimate size at about 3 CFP per second. You could size a 1,000 CFP set of requirements (about $1m of outsourced software) in about 2 or 3 minutes. You might then review the results to a) correct any requirements mistakes and b) verify the functional size of each requirement. Once verified by the analyst, the estimate becomes an exact count/measurement, which can even be used for fixed price outsourcing of software development work.
COSMIC Functional Sizing
Over the years, several variations of functional size metric have been created. Only five have achieved ISO recognition (COSMIC, IFPUG, Mark II, NESMA and FiSMA). IFPUG, Mark II, NESMA and FiSMA are all similar in that they are derived from the original ruleset created by Allan Albrecht at IBM back in the 1980’s. The COSMIC functional size methodology evolved from earlier methodologies, specifically designed to address the shortcomings of them. The key advantages that make COSMIC Sizing methodology more relevant to modern software are:
- It is based on software principles, dealing elegantly with interconnected software layers and software architectures.
- Estimates and measurements can be made before all requirements are known – highly suited to Agile development.
- It has been automated and so takes negligible learning.
Story points are prevalent across all Agile projects, they are a team-specific proxy measure for effort. Each team has a common understanding of the magnitude of a story point, it is typically in the order of a few hours of effort, but there are no strict rules. Story points are not a universal currency. They are not a standard and they cannot reliably be used to compare teams or projects. Story points are a useful internal indicator of anticipated effort, if no other means of estimation is available. Function points however are universal, standard and highly applicable to Agile development as much as any other development methodology. Click here to read more on the merits of CFP vs Story Points
Size is the Cornerstone of Software Estimation
Once you know the functional size in COSMIC function points (CFP), you can quickly establish other metrics that are directly related to size, such as cost, effort and schedule. Once the size in CFP is established you can then use industry conversion values that map function points to effort, cost and schedule. Rather than use industry conversions, you can use your own historical project data to establish your own velocity benchmarks.
Agile Estimation
Rather than burn time discussing story points or playing with Fibonacci cards. Agile estimation, in our experience is best achieved via functional sizing with COSMIC FP.
What can you estimates based on size?
- Velocity (average CFPs delivered per week)
- Schedule (number of weeks needed to deliver)
- Cost (total cost to design, develop, test and deliver)
- Effort (effort needed to design, develop, test and deliver)
- Quality (defect potentials for each constituent of the delivery)
How fast can you derive estimates?
Manually, a competent analyst can count (measure) function points at a rate of about 100-500 FP per day (approx $100k – $500k of software). This depends on the quality and clarity of the requirements and specifications. The speed also depend on the experience and ability of the analyst. With ScopeMaster you can expect to achieve these rules about 4 times faster.
Estimating As you Write User Stories
Using the ScopeMaster Story Analyser for Jira, you can estimate your stories’ functional size without even leaving Jira. The text of your user story is analysed by ScopeMaster’s powerful language engine to detect the functional intent and functional size.
Benchmarking with ScopeMaster
Take a few past projects, insert their requirements into ScopeMaster to get the functional size. Given that you already know the cost of that past project, you can now estimate the effort and schedule of the new project.
Size is not the only factor that determines software costs and schedule, but it is the most significant one. And the best measure of size is the COSMIC Function Point.
Problems with story points
- Inconsistent
- Game-able
- Non-linear
Story points are a team based opinion about the amount of effort it might take to build some software from a developer’s perspective. Story points are essentially a proxy for effort estimates, e.g. one story point might be the equivalent of 1 ideal person day. They are highly subjective and dependent on the opinions of the team. They vary from team to team and even over time within the same team. Their inconsistency and game-ability renders them impractical as a reliable engineering metric.
For those who consider estimation to be harmful, unimportant or just too difficult, check out Steve Mconnell’s excellent article on why estimation is an important and valuable skill that project managers need.
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