Some people feel that getting object-oriented programming (OO) is difficult and time-consuming process. Many of the cornerstones of OO programming benefit other programming paradigms as well. The article presents several types of couplings, used in computer science, for the study of OO. Dynamic coupling occurs when a piece of code uses another piece of code at runtime. This can get seriously out of hand using a style called the "train wreck." Temporal coupling appears when one has a dependency on time-either on things that must occur in a certain order, at a certain time, by a certain time, or worse, at the same time. Always plan on writing concurrent code because the odds are good that it will end up that way anyhow, and one can get a better design as a fringe benefit. Domain coupling takes place when business rules and policies become embedded in code. Again, that's not necessarily a bad thing unless mirroring real-world changes becomes difficult. If the real world is particularly volatile, put the business rules in metadata, either in a database or property files. Even in OO systems, view an object's behavioral interface as a set of function calls. That's really not a helpful metaphor. Instead of calling software a function, view it as sending a message.