Systems Engineering FAQ

Answers by Robert Halligan FIE Aust CPEng IntPE(Aus).

How do all these terms relating to requirements figure?


Problem definition is critically important to the achievement of stakeholder satisfaction. Here, I define a number of terms related to problem definition. Some definitions are perfectly general, and are therefore also applicable to an engineering context, whilst other definitions are specifically framed for engineering. Always try to use terms consistent with Miriam Websters or Oxford English dictionaries. By all means add precision to definitions for an engineering purpose, but avoid conflict – departing from community usage of language only creates confusion and mis-communication.

Here are some representative and recommended definitions of problem-domain terms, listed in alphabetical order:

1. an unsatisfied longing or craving (Oxford English Dictionary)
2. a conscious unsatisfied wish for something (Robert Halligan)

1. an instance of expecting or looking forward (Oxford English Dictionary)
2. something which is expected or predicted (Robert Halligan)

1. the object of a person’s ambition or effort; a destination; an aim (Oxford English Dictionary)
2. a desired characteristic of an item (product or service), usually for which a solution will be pursued, subject to trade-offs with other goals (Robert Halligan)
3. something to which one aspires for a program, or a point aimed at for achievement (United States Defense Systems Management College)

Measure of Effectiveness (MOE): a measure, beyond requirements, such that more or less of the characteristic represents a better solution (Robert Halligan)

Measure of Performance (MOP): a measure of how well something is done, or is to be done. Note that a MOP may, or may not, be an MOE. (Robert Halligan)

1. a condition of lacking or requiring some necessary thing, either physically or psychologically (Oxford English Dictionary)
2. something which is lacking in relation to some purpose (Robert Halligan)

Operational Effectiveness: a measure, beyond requirements, which brings together individual measures of effectiveness which are related to end use, into an overall measure (Robert Halligan)

Overall Effectiveness: a measure, beyond requirements, which brings together individual measures of effectiveness into an overall measure (Robert Halligan)

1. an order, a demand, an imperative, a dependence for success or fulfillment (Oxford English Dictionary)
2. some characteristic demanded or deemed an imperative, of something by someone (Robert Halligan)

Target: see “Goal”

1. wish for possession of (Oxford English Dictionary)
2. (noun) a wish for satisfaction of (Robert Halligan)
3. (verb) to wish for satisfaction of (Robert Halligan)


Answered By

Systems engineering thought leader, consultant, trainer and coach, impacting people's lives on six continents.
Published 1 year ago




Your success matters to us. Acquire new skills to excel in 2023. Register your interest today!

FREE Monthly SE Industry News?
Scroll to Top