Chapter 3: The Surgical Team

These studies revealed large individual differences between high and low performers, often by an order of magnitude.

 SACKMAN. ERIKSON. AND GRANT


When managing a team there is a debate between small teams made out of sharp first-class people, or bigger teams with people of every kind. Appart from that there are the needs and size of the project, for which a small team runs short or reseources for doing it in a meaningful schedule.


The Problem

Is it preferable to have small, sharp teams of very efficient programmers or a large team of no so efficient people able to deal with big tasks by, at the end, brute force?

The dilemma is a cruel one. For efficiency and conceptual integrity, one prefers a few good minds doing design and construction. Yet for large systems one wants a way to bring considerable manpower to bear, so that the product can make a timely appearance. How can these two needs be reconciled?


Mills’s Proposal – THE SURGICAL TEAM

Harlan Mills proposes that each segment of a large job be tackled by a team, but that the team be organized like a surgical team rather than a hog-butchering team. That is, instead of each member cutting away on the problem, one does the cutting and the others give him every support that will enhance his effectiveness and productivity.

Much as a surgical team during surgery is led by one surgeon performing the most critical work, while directing the team to assist with less critical parts, it seems reasonable to have a “good” programmer develop critical system components while the rest of a team provides what is needed at the right time

THE SURGEON  (The chief programmer).

  • Defines the functional and performance specifications, designs the program, codes it, tests it, and writes its documentation.
  • Writes in a structured programming language such as PL/I
  • Has effective access to a computing system which not only runs his tests but also stores the various versions of his programs, allows easy file updating, and provides text editing for his documentation.
  • Needs great talent (10+ years experience) and considerable systems and application knowledge, whether in applied mathematics, business data handling, or whatever.

THE COPILOT. (The alter ego of the surgeon)

  • Able to do any part of the job, but is less experienced.
  • Main function is to share in the design as a thinker discussant, and evaluator. The surgeon tries ideas on him, but is not bound by his advice.
  • Represents his team in discussions of function and interface with other teams.
  • Knows all the code intimately.
  • Researches alternative design strategies.
  • May even write code, but he is not responsible for any part of the code.

THE ADMINISTRATOR

  • Is boss, and he must have the last word on personnel, raises, space, and so on, but he must spend almost none of his time on these matters.
  • Needs a professional administrator who handles money, people, space, and machines, and who interfaces with the administrative machinery of the rest of the organization.
  • Has a full-time job only if the project has substantial legal, contractual, reporting, or financial requirements because of the user-producer relationship.

THE EDITOR

  • Takes the draft or dictated manuscript produced by the surgeon and criticizes it, reworks it, provides it with references and bibliography, nurses it through several versions, and oversees the mechanics of production.

TWO SECRETARIES

  • The administrator and the editor will each need a secretary; the administrator’s secretary will handle project correspondence and non-product files.

THE PROGRAM CLERK

  • Responsible for maintaining all the technical records of the team in a programming-product library.
  • The clerk is trained as a secretary and has responsibility for both machine-readable and human-readable files.
  • Logs and keys it all computer input. The output listings go back to him to be filed and indexed.
  • Making all the computer runs visible to all team members and identifying all programs and data as team property, not private property.
  • Relieves programmers of clerical chores, systematizes and ensures proper performance of those oft-neglected chores, and enhances the team’s most valuable asset—its work-product.
  • Logs all updates of team program copies from private working copies, still handles all batch runs, and uses his own interactive facility to control the integrity and availability of the growing product.

THE TOOLSMITH

  • Responsible for ensuring the adequacy of “File-editing, text-editing, and interactive debugging” services and for constructing, maintaining, and upgrading special tools—mostly interactive computer services—needed by his team.
  • Each team will need its own toolsmith
  • The tool-builder will often construct specialized utilities, catalogued procedures, macro libraries.

THE TESTER

  • Is both an adversary who devises system test cases from the functional specs, and an assistant who devises test data for the day-by-day debugging.
  • Also plans testing sequences and set up the scaffolding required for component tests.

THE LANGUAGE LAWYER

  • Masters the intricacies of a programming language, which uses to do difficult, obscure and tricky things
  • Does small studies on good technique
  • At the service of different surgeons


How It Works

The team just defined meets the desiderata in several ways. Ten people, seven of them professionals, are at work on the problem, but the system is the product of one mind—or at most two, acting uno animo.

Differences between a team of two programmers conventionally organized and the surgeon-copilot team.

  • In the conventional team the partners divide the work, and each is responsible for design and implementation of part of the work. In the surgical team, the surgeon and copilot are each cognizant of all of the design and all of the code. This saves the labor of allocating space, disk accesses, etc. It also ensures the conceptual integrity of the work.
  • In the conventional team the partners are equal, and the inevitable differences of judgment must be talked out or compromised. Since the work and resources are divided, the differences in judgment are confined to overall strategy and interfacing, but they are compounded by differences of interest. In the surgical team, there are no differences of interest, and differences of judgment are settled by the surgeon unilaterally.

These two differences—lack of division of the problem and the superior-subordinate relationship—make it possible for the surgical team to act uno animo.

Yet the specialization of function of the remainder of the team is the key to its efficiency, for it permits a radically simpler communication pattern among the members.

Chapter 2: The Mythical Man Month

Good cooking fakes time. If you are made to wait, it is to serve you better, and to please you

MENU OF RESTAURANT ANTOINE. NEW ORLEANS


More projects go wrong because of lack of time than other factors.

  • Estimation techniques are poorly developed (optimistically assuming that “all will go well”)
  • Estimation techniques fallaciously confuse effort with progress (assuming men and time are interchangeable)
  • We are uncertain of our estimates
  • Schedule progress is poorly monitored
  • When schedule delay is identified, the natural (and traditional) response is to add manpower (which makes matters worse, much worse)


Optimism

All programmers are optimists. Why?, maybe…

  • this modern sorcery (programming) especially attracts those who believe in happy endings and fairy godmothers.
  • the hundreds of nitty frustrations drive away all but those who habitually focus on the end goal.
  • it is merely that computers are young, programmers are younger, and the young are always optimists.

Whatever the case, mottos are usually: “This time it will surely run” or “I just found the last bug”. Dorothy Sayers (on her book – The Mind of the Maker) divides creative activity into three stages:

  • IDEA – a program comes into existence first as an ideal construct, built outside time and space, but complete in the mind of the author
  • IMPLEMENTATION – built in time and space, by pen, ink, and paper, or by wire, silicon, and ferrite.
  • INTERACTION – when the user is making use of it

Traditional activities reveal the incompleteness and inconsistencies of our ideas during implementation, which takes time and sweat both because of the physical media and because of the inadequacies of the underlying ideas.

On the other hand, the programmer builds from pure thought-stuff, in a very tractable medium. Because of it, we expect few difficulties in implementation; hence our pervasive optimism. But our ideas are faulty, so have bugs; hence our optimism is unjustified.

In a single task, the assumption that “all will go well” has a probabilistic effect on the schedule where it might not go well.

A large programming effort, however, consists of many tasks, some chained end-to-end. The probability that each will go well becomes vanishingly small.


The Man-Month

It is erroneous to consider that people and months are interchangeable, which is reflected in the unit of effort used in estimating and scheduling: the man-month.

  • Cost varies according to the number of men and the number of months.
  • Progress does not.

The man-month as a unit for measuring the size of a job is a dangerous and deceptive myth.


TYPES OF DIFFERENT TASKS AND ITS MEN-TIME INTERCHANGEABILITY:

  • Tasks that can be partitioned (with no need for communication among workers):
    Men and months are interchangeable commodities as it presents workers with no communication among them.
    EXAMPLE: reaping wheat or picking cotton
  • Tasks that cannot be partitioned because of sequential constraints
    The application of more effort has no effect on the schedule.
    EXAMPLE: The bearing of a child takes nine months, no matter how many women are assigned.
  • Tasks that can be partitioned (with needs for communication among the subtasks)
    The effort of communication must be added to the amount of work to be done. Therefore the best that can be done is somewhat poorer than an even trade of men for months.

The added burden of communication is made up of two parts

  • TRAINING: in the technology, the goals of the effort, the overall strategy, and the plan of work. This training cannot be partitioned, so this part of the added effort varies linearly with the number of workers.
  • INTERCOMMUNICATION:  If each part of the task must be separately coordinated with each other part/ the effort increases as n(n-I)/2. Three workers require three times as much pairwise intercommunication as two; four require six times as much as two.

If, moreover, there need to be conferences among three, four, etc., workers to resolve things jointly, matters get worse yet. The added effort of communicating may fully counteract the division of the original task.

Software development is inherently a systems effort—an exercise in complex interrelationships—communication effort is great, and it quickly dominates the decrease in individual task time brought about by partitioning. Adding more men then lengthens, not shortens, the schedule.


Systems Test

Sequential constraints especially affect component debugging and system test. The time required depends on the number and subtlety of the errors encountered. (Theoretically this number should be zero.)


>> OPTIMISM
>>  We expect less bugs than it turns out to be
>> testing runs out of (mis)scheduled time


Rule of thumb for scheduling a software task:

  • l/3 planning
  • l/6 coding
  • l/4 component test and early system test
  • l/4 system test, all components in hand.

This differs from conventional scheduling in several important ways:

  1. The fraction devoted to planning is larger than normal. Even so, it is barely enough to produce a detailed and solid specification, and not enough to include research or exploration of totally new techniques.
  2. The half of the schedule devoted to debugging of completed code is much larger than normal.
  3. The part that is easy to estimate, i.e., coding, is given only one-sixth of the schedule.

Not assigning enough time for test is disastrous. Delay on testing phase comes at the end, so it is realized in the verge of delivery date. Bad news, late and without warning; for both customers and managers.

Consequences:

  • Direct costs on development project.
  • Indirect costs to the functionalities for which this project is being developed.


Gutless Estimating

Urgency on the managerial side affects the schedule, but has nothing to do with the real time required for development. Once estimated time has been passed, customer has two choices—wait or “eat it raw”.

False scheduling to match client’s desired date is much more common in Software Development than elsewhere in engineering.

It is extremely complicated to make a real plausible estimation derived by no quantitative method, not enough data which is accepted by managers.

Clearly two solutions are needed. We need to develop and publicize productivity figures, bug-incidence figures, estimating rules, and so on. The whole prof ession can only profit from sharing such data.

Until estimating is on a sounder basis, individual managers will need to stiffen their backbones and defend their estimates with the assurance that their poor hunches are better than wishderived estimates.


Regenerative Schedule Disaster

Problem: a project behind schedule.
Possible solutions:

  • Include extra people to meet time requirements. This will imply additional –and not available time- for training, additional testing,… creating a new delay.
  • Reschedule, allowing time enough to ensure the work to be carefully and thoroughly done (so, no need for future rescheduling)
  • Trim the task (which in practice trends to occurred anyway when adding additional people)

Oversimplifying outrageously: BROOK’S LAW:


“Adding manpower to a late software project makes it later”


This then is the demythologizing of the man-month:

  • The number of months of a project depends upon its sequential constraints.
  • The maximum number of men depends upon the number of independent subtasks.

From these two quantities one can derive schedules using fewer men and more months. (The only risk is product obsolescence.) One cannot, however, get workable schedules using more men and fewer months. More software projects have gone awry for lack of calendar time than for all other causes combined.