Agile Software Development
Автор: Alistair Cockburn /
CHAPTER 3. Communicating, Cooperating Teams Convection Currents of Information
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Часть 2
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The main question is, if you were funding this project, which working www.babypic.ru configuration would you like Kim and Pat to use?
What we see is that even minor differences have an impact on the rate of information flow.
Figure 3-3. Pair programming and working across a partition. Between which pair of people will information discovery happen fastest? (photo courtesy of Thoughtworks, Inc. )
Notice, in Figure 3-3, the two different situations in play at the same time. The two people on the left are pair programming. It may be nice for them to have a small separation from the person on the right. However, if it happened to be the two people across the partition who needed to work together, the partition would soon become a problem. Indeed, I visited two people working across a partition, and it wasn't long before they removed the partition. As one of them explained, "I couldn't see his eyes"!
Erg-seconds
Comparing the flow of information with that of heat and gas is not as far-fetched as it may at first seem. With every speech act, Kim radiates both information and energy into the environment around her. That information or energy gets picked up by people within sight or hearing. Pat also radiates, with every speech act.
In his case he radiates his need for information. Sooner or later, either Kim detects Pat's information need, or Pat detects that Kim has the information. Whichever way the discovery goes, they then engage in conversation (or Pat reads Kim's document, if Kim's information is in written form, ).
In gas dispersion problems, one analyzes the distance molecules travel in a certain amount of time. The unit of measure for molecules is moles, that for distance is meters, so gas dispersion is measured in mole-meters / second (how many moles of the gas travel how far, in how much time).
We can analyze the movement of ideas (memes, to borrow an appropriate term from The Selfish Gene (Dawkins 1990)) using similar terms. We are interested in how many useful memes flow through the project team each minute.
Meters is not the correct unit, though, since ideas travel through phone lines, email and documents, rather than through space.
What we care about is the amount of energy it takes to move a meme from one head to another. The appropriate units are erg-seconds. Ergs is a unit of work (such as walking up the stairs), and seconds is a unit of time (such as time spent on the telephone), so erg-seconds captures the cost in both labor and time to get a question answered.
(Bo Leuf comments that its inverse is also useful: argh-seconds, a measure of the pain of expending energy and not managing to convey the idea).
Using this metaphor, let's look at office layouts to see the energy cost associated with detecting that someone else has some needed information.
Supose Kim and Pat sit in offices some distance from each other (Figure 3-4). The walls between them keep Pat from seeing or hearing Kim. Kim radiates information as she walks around on her daily travels.
The people in her room detect the greatest amount of information, and the people in earshot of her movement detect the next greatest amount. Information reaches Pat either as Kim walks into his office, or indirectly, through other people.
Figure 3-4. Energy and information moving through a barrier complex.
If their offices are next to each other, Kim is more likely to pop into Pat's office, or vice versa (Figure 3-5, top). Just as gas molecules or convected heat more easily move betweeen neighboring rooms, so also does project information.
Figure 3-5. Gas cannisters (or people) in three different configurations.
If Kim and Pat share an office (Figure 3-5, middle), then just as Pat will smell Kim's perfume sooner, so will he notice if Kim radiates information useful to him.
The greatest rate of movement of information is if they are sitting side by side. In the case of information, the information transmission is greater if they are working on the same task, pair programming, than if they are merely sitting side by side, working on different tasks (this has to do with their focus of attention more than the radiation).
The units of erg-seconds captures the effect of distance and communication modality on project costs.
Assume face to face communications, sitting in your own office, versus walking 50 meters to a colleague's office. Walking down the hall takes work (ergs) and time (seconds). Energy and cost go up, and the information transfer rate goes down. Move people closer. .. to the office next door. As the distance goes down, work required to visit the colleague goes down, and so do energy and project cost, while the information transfer rate goes up.
Similarly, describing an idea on the phone takes more time than describing it is person. In this case, the time factor increases, and so does cost to the project.
So the formula erg-seconds gives good advice in these areas.
Of course, the formula does not tell us about wasted energy, such as jumping up and down while talking on the phone, or walking around the building the long way in getting to a colleague's office. It also does not guarantee that putting two people in the same ensure that they ever actually understand each other (see "The Impossibility of Communication" in the Introduction). What it does say is that project costs go up as people take longer to understand each other
Osmotic Communication
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