Dynamics
The description of the layers of change establishes not only the relations among different layers during the construction, but also dynamic relations between the different component layers during use. The stability of change in a building is based on the layers that change slowly over time. Listing the layers in order of the rate of change from slow to quick, we have: Software Site supports Software Structure, which stabilises Software Skin, allows connections of Software Services and brings together Software Space Plan, which is composed of Software Stuff. In Software, as in a building, the slow parts have the same objective: to provide stability to the system. Difficult problems arise when attempting to modify slow parts at a faster rate than it is allowed.Influence also goes in the other direction: at times of radical change, the quickly changing layers influence the slow ones: slower layers tend to gradually integrate the trends of the quick layers within them.
In summary, the slow parts of a software system provide continuity and constraint, while the quick parts provide originality and change. "The speedy components propose, and the slow dispose" [Brand94].
Jorge Luis Ortega Arjona