Prioritization and Value Maximization [Tyner Blain]

Very powerful introduction to the value-driven approach.

Tom Gilb's Concept Glossary

Tom Gilb has updated his Concept Glossary, including my comments on his definition of the requirement concept (below), which he is kind enough to describe as "a particularly well thought out notion of requirement".

(The numbers in parentheses, preceded by an asterisk, refer to other concepts in Tom's glossary. The numbers in brackets refer to footnotes in the original; these follow the main text.)

1. The people whose ends a system (*145) serves are one class of stakeholders. They value the actual results, or receive benefit (*009)[1].
2. The people who consider the future of a system and/or agree to the suggestions of others are a different class of stakeholders. They perceive potential value (*269).
3. If these people take ideas forward (deciding to act or persuading others to decide to act, or considering the desirability of action), they can be described as “Founders”[2] of the resultant system or course of action.
4. The arena within which action may occur is variously described as the “problem domain”, “scope” (*419) or “context”[3].
5. A perception of value within a particular context for action is a potential requirement.
6. A potential requirement coupled with authority (*005) or discretion[4] to pursue its satisfaction is a requirement. The person[5] who confers the authority is the requirement’s “Sponsor”.
7. So, a requirement is a perception of value in a particular context for action coupled with the authority to pursue[6] its satisfaction: the authorized and contextualized pursuit of value.
8. The substance of a requirement (what is required) is the value. That of which it is a requirement is a future system[7]. The context within which it is a requirement includes the project or endeavor (“development environment”) and the anticipated operating environment. Explicit or implicit authority to pursue the requirement (within a particular context[8]) is a status of the requirement (in that context).

There are footnotes in the original:

[1] Because these stakeholders can only receive benefit from an operational system, they can be referred to as “operational stakeholders”.
[2] Or “Originators”
[3] This is not the same as Context (*483). None of these terms is entirely satisfactory, but “context” comes closest to the idea of a simple “frame of reference” or environment within which action may take place (including the operation of a system).
[4] “Discretion” might best be described here as “implicit authority”. Implicit or explicit authority could be regarded as the result of “stakeholder prioritization”.
[5] Ideally, a requirement should have a single Sponsor. A group may be collectively responsible, but even then, it is preferable for one among them to take on the role of Sponsor.
[6] “…for the time being” could be added, authority always being conditional. If the conditions are not met, the authority is no longer valid and, as an immediate and automatic consequence, the “requirement” reverts to being a “potential requirement”.
[7] Strictly, either a sub-system or an attribute (*003) of the system (*145).
[8] We can distinguish here between transitional context (e.g. a project) and operational context (where “environment” is a common alternative term). If the transitional context is undefined, we can refer to the requirement as an “orphan requirement”. If the operational context is undefined, we can only say that the Requirement Specification (*508) is defective; the status of the requirement itself is undecidable (but decidedly not authorized).

Roger Cauvin's Requirement Definition

I have never subscribed to the IEEE "definition" of requirement, and I'm not convinced that Roger's adaptation makes it acceptable. It certainly makes it more acceptable, so "well done, Roger!"

Where do we go from here?

First, can we equate "least stringent condition" to Tom Gilb's "Fail" concept (*098), "the leading edge of a Failure Range"?

If so, what do we do with the other interesting points on Gilb's continuum, reproduced (slightly modified) below?

•••••••[!!!!!!====>____>••••••[!!!!!!====>____>

•• is a catastrophe range.
[ is a lower survival level.
!!!!! is a Failure Range.
==== is an acceptable range.
> is a Goal level.
_____ is a success range.


My view would be that the requirement, if not more fully characterized in some way similar to Gilb's, is for "success", as opposed to the avoidance of "failure" or "catastrophe". It is the latter that Roger's "least stringent condition" suggests (to me).

Of course, I find even Gilb's exposition simplistic, but we have to run before we can walk! For practical purposes, it is useful to reduce the requirement concept to "measurable, valued outcomes". Observing or hypothesizing how much, and how differently, changes to outcomes are valued by diverse stakeholders is a powerful technique for establishing what might constitute success, but it is still one-dimensional. Leaving the whole multi-dimensional trade-off between benefits (including but not limited to avoided costs) to one side, what emerges from such an exploration is (hopefully) agreement about the level of outcomes to pursue. I would call this an objective rather than a requirement but, to me, objectives are a type of requirement.

What, though, of "raw" function? Here it is crucial to be very precise about the context. It is, in practice, always possible to move backwards and forwards along a cause-and-effect chain, dragging the "system boundary" one way or another (hypothetically, at least). Determining the "border zone" is, in my view, a requirements activity. This is what constructing use-cases is all about. The problem, it seems to me, is that use-cases implicitly assume an immovable boundary. The reality is that some boundaries are clearer than others; some more the result of design, some more a matter of policy or practical constraints. Defining a range of required function is key.

In this view, we recognise a distinction between "core" function, the absence of which is unacceptable, and "contingent" function, which must be present in some form in the universe, but not necessarily in the system being specified. Performance characteristics are unavoidable for all function. The valued performance characteristics are what drive the distinction between "core" and "contingent", I think, and, more relevantly, inform the ultimate decision about what "contingent" function is a necessary, desirable, unnecessary or undesirable inclusion in the final system.

A random blog: Seilevel Presentation

A random blog: Seilevel Presentation

I've made a few contributions to the Seilevel forum, though I'm not convinced we're on the same wavelength.

...about checking rates

...about Tom Gilb, Agile and INCOSE 2007

...about Maslow's Hierarchy of Needs, mobile phones, trading off performance

...about decision-making processes

Three Cheers for the Worry-Stack (prioritization)

Let the Market Decide (prioritization)

...how worse can be better

...the final word on Goals vs. Businesss Objectives

...to copy or link: maintainability vs. usability

Effective Requirement Process

I waited a month before replying to a question on one of Tom Gilb's forums. This is only partly because I wanted to avoid doing the student's assignment. The main reason was so that I could canvass opinions on LinkedIn's new(ish) Answers facility. Interesting results from LinkedIn were:

1. A general distrust of KPIs (Key Performance Indicators)
2. The absence of any reference to possible KPIs, however flawed or dangerous
3. A belief in the impossibility of measuring the effectiveness of requirement processes
4. A fairly low number of responses (7). Is that because it's a hard question or an uninteresting one, I wonder.

I may yet re-open the question with my own thoughts included as clarification. For the moment I must leave a little time for others to comment on my Gilb post.

Tom Gilb's Forum

I've been contributing to Tom Gilb's forum for longer than it has existed. Some of the posts are a little difficult to find so long after the event. There are apparently 10 of them, but I can only find these 6...

Re: Theory on why it is hard to distinguish Requirements from Design, in Project Management & Product Development

Re: Gilb 88, in Project Management & Product Development

Re: Re: Definition, in Inspection, Quality Control & Defect Prevention

Re: Definition, in Inspection, Quality Control & Defect Prevention

Re: Classifying defects as Major/minor in Inspection, Quality Control & Defect Prevention

Design Methods, in Design, Industrial Design, Solutions

I also have a Gilb wiki home page, which links into my Gilb wiki contributions.

Forum Posts

I should get round to extracting specific forum posts soon enough, but contributions so far have been principally to:

Tom Gilb's website, http://www.gilb.com

The Seilevel Requirements Discussion forum, http://requirements.seilevel.com/messageboard/forumdisplay.php?f=3