Recall that providing a simplified overview of human capabilities and pursuits is of key importance. As discussed earlier, the problem of scope vs. resolution always will be present when one is deciding how much detail is relevant at a particular level. We have tended not to name as clusters those which would basically represent sub-disciplines of well-established fields like medicine, engineering and law. They are quite easy to locate within the Directory without their being designated as formal skill clusters. On the other hand we have tended to include cluster names which serve to break up larger, less familiar fields like science which have experienced very rapid proliferation in recent history.

Repeating what was said above about categories, levels and boundaries. Approach these notions flexibly. Boundaries between various groups and between various levels are not completely impermeable.  The fifty-two (52) Skill Clusters should be thought of as loosely-coupled and partially overlapping.  Intra-frame coupling and overlap is greater than inter-frame coupling and overlap.

We have tried to maintain the distinction between the skill and the object to which the skill may be applied. In contrast with other skills vocabularies the Skills Directory tends to focus on actual skills and to avoid cataloging objects, conditions and situations which may demand that the skill or ability be exercised. For example, many ENGINEERING skills are included, but the products of these skills generally are excluded (i.e. sensors, motors, actuators, integrated circuits, rotary machinery, propulsion systems, etc).