- complicated - dealing issues related to cardinality either of the sets themselves or their relationships. Anything that is computationally hard (and there is a whole bunch of disciplines dealing with this type of thing) is a good example. We like to use tricks like combinations versus permutations, yet doing so requires extensions that are not a given. How many modern situations cannot resolve down to a static state? An example: to control malicious manipulation of this fact, we have Sarbanes-Oxley.
- difficult - gnarly types of things, essentially. Mathematics and the hard sciences are full of these. So too are the 'softer' sciences (yet, these we can pass off, perhaps, as unnecessary complications).
In the context of problem solving, such as earned-value determinations, both of these come into play. Sometimes the issue of resolving schedule and status is as much of a can of worms as establishing the value of a financial instrument. So, finding similarity of approaches is not unexpected.
What truth engineering will bring to this issue will be something to discuss.
11/21/2010 -- This was first written three years ago and is still apropos. However, we need to get technical to talk how to get ourselves un-twined.