Unfortunatley this has also proven that ideal doesn't work out very well.

Computers, for instance, may be used by people without Computer skill. They can't Write Programs or Defeat Security, but they can use programs for what they were written for. Slingshot Simmons (p. 46) doesn't need Computer skill to use the Analysis, Commerce, and Information Storage programs on his business computer, but he DOES have to take some time to learn how to use them. Think of it as having to learn a whole new word processor on every new computer you buy.

Consider the character Geeko-sur-Mang from "Crash on Volturnus." He/she (he from now on) is a "professor of geology" and a "recognized authority in geoophysics, specialist in planetary crust formation." His skills are computer level 4 and... that's it. He is not an environmentalist, even though environmentalists are trained in geology.

In some games there is a long list of skills, and if you don't have a skill you can't do that thing. To perform the skill you must be rated in that skill, even if that rating is "unskilled." In SF the skills do not preclude the ability to do perform a task without that skill. A skill is just a convenient package of things you can do, and it's never true that if you don't have the skill you can't do one of those things. The skills are not exclusive.

So while a technician has the ability to "operate machinery," which includes driving ordinary vehicles, that doesn't preclude anybody with the appropriate background from knowing how to drive skimmers or ground cars. If it makes sense that your character can drive a skimmer, he can drive a skimmer. It's all handled by the referee in the best Free Kriegsspiel tradition.

A mathematician doesn't need to be a computer specialist to use the analysis program in his computer. An astronomer doesn't need to be an environmentalist to plot planetary orbits. But PCs aren't assumed to be mathematicians or astronomers so there are no skills covering the things these kinds of people want to do. Even PCs can do things not granted by a skill, like driving a skimmer.

A geologist trying to answer a question about geology would roll against Logic. For a question the average geologist would find to be of average difficulty (roll against unmodified Logic), Geeko-sur-Mang would find easy to answer—with perhaps a +30 bonus to Logic. An environmentalist, with a little training in geology, might find this a difficult question, perhaps a ?10 penalty to Logic.

Any time a character wants to perform an action requiring training of some sort, the referee decides which ability handles that action and how difficult the action is, including factors such as the background training of the character.

Remember, they're called abilities, not attributes, for a reason!

And the coinciding KH Skills to boot.

I had some concerns over it because there were some AD subskills that became much easier and others much harder to accomplish in the process. There are some AD subskills that are 100% chance but not automatic : diagnosis is 100% but should it be performed on an alien non core four species there is a -20% mod and of course a referee can add other modifications like -10% because the condition is hard to identify on his say so and etc. 

For this reason I wrote an article on task modifiers for SF which borrowed from HARP RPG. I'd have to look up which issue in the SFman.

I've been deeply in favor of all skill checks are 1/2 ability +10%/level (plus other modifiers that apply of course) for the simple reason of speed of play. Everyone at the table remembers it. Only the character sheet need be consulted. And gameplay moves along at a very past pace. Otherwise you will be looking up a quick reference sheet for every skill check.