The Psychology of Quality and More
Planguage for Requirements
One of the most common reasons that projects fail is confusion over what is really wanted. This typically starts in the requirements phase, where what is needed should be clearly defined, but seldom is. Weak requirements lead to propagated error with specifications, designs and build that do not really meet original customer needs.
A second, related problem that follows from the first is creeping requirements. Customers changing their minds and changing the requirements is much easier when the requirements are not clear. If you have a precise definition of what is needed, then it is easier to control.
A good tool for addressing this is provided by Tom Gilb in his book ‘Competitive Engineering’. ‘Planguage’ stands for ‘planning language’ and is simpler than it sounds. The basic principle is to use a set of closely defined identifiers (‘tags’) to describe and quantify specific elements of the requirements.
Here is a simple partial example of using Planguage:
PLAN [01-Sep 2012]: Full product release
The format as can be seen is:
There is somewhat more in Planguage, although much can be done with relatively few keywords, as shown in the table below.
A requirements document will often need more narrative than is provided by a Planguage format, though this approach is very good for definitive descriptions in the parts that need close attention (which is often more than is realised). It is also useful in legal documents such as contracts and proposals where people may be held to account for specific items.
The critical principle of Planguage is precision. It forces you to think carefully and define everything. It is also a good facilitation tool with which you can sit down with others and work through their ideas and requirements. Most of all, it gives you a definitive document that will lead to a higher quality, on-time product.
The Planguage Concept Glossary can be found here: http://www.gilb.com/tiki-page.php?pageName=Competitive-Engineering-Glossary
Next time: Quality Cost Audit
This article first appeared in Quality World, the journal of the Chartered Quality Institute
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