Articles Heuristics for System-Level Architecting
      

Heuristic Tool List

1 Multitask Heuristics

D Performance, cost, adn schedule cannot be specified independently. At least one of the three must depend on the others.
D With few exceptions, schedule delays will be accepted grudgingly (reluctantly); cost overruns will not, and for good reasons.
D

2 Scoping and Planning

The beginning is the most important part of the work. Plato, 4th century B.c
Scope! Scope! Scope! William C. Burkett, 1992
D Success is defined by the beholder, not by the architect.
p The most important single element of success is to listen closely to what the customer perceives as his requirements and to what the willing and ability to be responsive. (J. E. Steiner 1978)
P Ask early about how you will evaluate the success of your efforts. (E. Hayes-Roth et al., 1983)
P For a system to meet its acceptance criteria to the satisfaction of all parties, it must be architected, designed, and built to do so — no more and no less.
P Define how an acceptance criterion is to be certified at the same time the criterion is established.
D Given a successful organization or system with valid criteria for success, there are some things it cannot do—or at least not do well. Don't force it.
P The strengths of an organization or system in one context can be its weaknesses in another. Know when and where.
D There's nothing like being the first success.
P If at first you don't succeed, but the architecture is sound, try, try again. Success sometimes is where you find it. Sometimes it finds you.
D A system is successful when the natural intersection of technology, politics, and economics is found.
D Four questions, the Four Who's, need to be answered as self-consistent set if a system is to succeed economically; namely, who benefits, who supplies, who pays, and, as appropriate, who loses
D Risk is (also) defined by the beholder, not the architect.
P If being absolute is impossible in estimating system risks, then be relative.
D No complex system can be optimum to all parties concerned, nor all functions optimized.
P Look out for hidden agenda.
P It is sometimes more important to know who the customer is than to know what the customer wants. (Whankuk Je 1993)
D The phrase, "I hate it," is direction. (Lori I. Gradous 1993)
P Sometimes, but not always, the best way to solve a difficult problem is to expand the problem, itself.
P Moving to a larger purpose widens the range of solutions (Gerald Nadler 1990)
P Sometimes it is necessary to expand the concept in order to simplify the problem. (Michael Forte 1993)
P [If in difficulty,] reformulate the problem and re-allocate the system functions. (Norman P. Geis 1991)
P Use open architectures. You will need them once the market starts to respond.
P Plan to throw one away. You will anyway. (F.P. Brooks, Jr. 1982)
P You can't avoid redesign. It's a natural part of design.
P Don't make an architecture too smart for its own good.
D Amid a wash of paper, a small number of documents become critical pivots around which every project's management revolves. (F. P. Brooks, Jr. 1982)
P Just because it's written, doesn't make it si. (Susan Ruth 1993)
D In architecting a new [software] program, all the serious mistakes are made in the first day.
P The most dangerous assumption are the unstated ones. (Douglas R. King 1991)
D Some of the worst failures are systems failures.
D In architecting a new [aerospace] system, by the time of the first design review, performance, cost, and schedule have been predetermined. One might not know what they are yet, but to first order all the critical assumptions and choices have been made which will determine those key parameters.
P Don't assume that the original statement of the problem is necessary the best, or even the right, one.
P Extreme requirements, expectations, and predictions should remain under challenge, throughout system design, implementation, and operation.
P Any extreme requirement must be intrinsic to the system's design philosophy and must validate its selection. "Everything must pay its way on to the airplane." [Harry Hillaker 1993]
P Don't assume that previous studies are necessary complete, current, or even current. (Jame Kaplan 1992)
P Challenge the process and solution, for surely soneone else will do so. (Kenneth L. Cureton 1991)
P Just because it worked in the past there's no guarantee that it will work now or in the future. (Kenneth L. Cureton 1991)
P Explore the situation from more than one point of view. A seemingly impossible situation might suddenly because transparently simple. (Christopher Abts 1998).
P Work forward and backward. (A set of heuristics from Rubinstein 1975)
Generalize or specialize.
Explore multiple directions based on partical evidence.
Form stable substructures .
Use analogies and metaphors.
Follow your emotions.
P Try to hit a solution that, at worst, won't put you out of business. (Bill Butterworth as reported by Laura Noel 1991)
P The order in which decisions are made can change the architecture as much as the decision themselves. (Rechtin 1975, IEE SPECTRUM)
P Build in and maintain options as long as possible in the design and build of complex systems. You will need them. OR ... Hang on to the agony of decision as long as possible. [Robert Spinrad 1988]
P Successful architectures are proprietary, but open. [Morrison and Ferguson 1993]
D Once the architecture begins to take shape, the sooner contextual constraints and sanity checks are made on assumptions and requirements, the better.
D Concept of formulation is complete when the builder thinks the system can be built to the client's satisfaction.
D The realities at the end of the conceptual phase are not the models but the acceptance criteria.
P Do the hard parts first.
P Firm commitments are best made after the prototype works.

3 Modeling

P If you can't analyze it, don't build it.
D Modeling is a craft and at times an art. (William C. Burkett 1994)
D A vision is an imaginary architecture ... no better, no worse than the rest of the models. (M. B. Renton Spring 1995)
D From psychology: If the concepts in the mind of one person are very different from those in the mind of the other, there is no common model of the topic and no communication. [Taylor 1975] OR .. From telecommunicaiton: The best receiver is on that contains and internal model of the transmitter and the channel. [Robert Parks & Frank Lehan 1954]
D A model is not reality
D The map is not the terittory. (Douglas R. King 1991)

    References

    (1) The Art of System Architecting, Mark W. Maier, Eberhardt Rechtin, Third Edition.

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