maandag 4 april 2011

Prioritiy

"Everything has priority number 1"
"These features are all 'must haves', I have limited myself to the bare minimum"

Who does not recognize these reactions from his or her users?

Why do we put priorities? The general reason is inside the old rule about supply and demand: There is always more demand for features than time to realize them. This applies in all stages of an IT-system, and broader, in all stages of projects and products. In IT, it not only applies to features, but also to other requirements, to change requests, and to the solution of bugs.

The IREB foundation mentions several ways to determine the priority of requirements, and, surprisingly, not the most well know method of prioritization of all, the MoSCoW scale.

The first method is assigning a high/medium/low scale. Many development tools use such as system.

A second way, not mentioned by IREB, is the MoSCoW method. Basically, MoSCoW is an acronym of the the four levels of priority:
* Must - A Must have, without this feature the system/product has no valid reason tot exist.
* Should - should have this if at all possible in this timebox, the difference with "Must" is a matter of time. For example, not all reports are needed at the start of the operations.
* Could - These are often viewed as 'nice to have', and often a few minor things which cost few resources are taken up.
* Would - things which we would like to have if we had sufficient time - which we usually have not.

A third way is Carl Wiegers prioritization matrix. Basically he lists all features, and assigns each of them 4 values, ranked on a scale of 1-10:
- relative benefit
- relative penalty for not having
- relative cost
- relative risk
These four numbers are processed for each feature, and the result gives an indication of a features value.

The Kano model mentioned in a previous post roughly classifies features in three groups:
* Base factors: the factors without which a product will not be bought. For example, a laptop without screen, or a car without wheels. A customer wont mention them, he will take them for granted.
* Performance factors: those factors for which more is better. For example the number of colors in which a customer can buy a car, or the number of years of guaranteed problem free service of a coffee machine.
* Excitement factors: Those attributes which make a customer say: "wow!". These factors tend to degenerate into performance factors over time. For example an autopilot in a car would be a wow factor now, but may be common place in 10 years. An IT-system which gives AI powered hints might be a wow now, but the users will get used to it in a few years - if it takes them that long to get used to it.

Another way is to use a matrix with two different dimensions on the two axis. Two dimensions which spring to mind are impact or profitability, and effort.



In the example matrix to the left features A-F have been plotted in effort vs impact. A and E ave moderate high impact and moderate high effort. Features D and F, in the upper left quadrant, have low effort but high impact. It will be clear that these features should be considered as high priority.

Another good combination of dimensions to pair of, are impact and urgency. This one already has a name, it is called the Eisenhower matrix. For example, an incident with great impact may still have low urgency. It is essential to have clear, unambiguous definitions of both. For incidents in the operation of an IT-system, impact may be defined in terms of the number of users being affected. Urgency is easier to explain in medical terms: bleeding, suffocating and starvation may all cause death, but suffocation is the most urgent, followed by bleeding, with starvation coming last.
Let's have a look at some examples for IT systems and features. Let's define impact as related to the number of users affected, and let's define urgency as:
- essential to primary process, no workaround
- essential to primary process, workaround available
- not essential to primary process
Feature A specifies that every user will be able to print reports with the first sheet on special company paper. Obviously it scores high on impact, but urgency will be low - the first sheet on special paper is not something that is essential to a companies primary process.
Feature B specifies that the customers can purchase items through the website, and that this is the only sales channel. It will be clear that this scores high on both impact and urgency.


Sources:
* http://en.wikipedia.org/wiki/MoSCoW_Method - MoSCoW method
* http://www.processimpact.com/articles/prioritizing.html - Carl Wiegers priority matrix.
* http://it-maintenance.blogspot.com/2010/11/kano-model-explained.html - Kano model
* http://ireb.de/ - ireb.
* http://beanoriginal.net/deadlines-and-the-urgency-side-of-the-eisenhower-matrix/ - eisenhower matrix

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