At the moment, I think that Kannagara will involve two kinds of ability: knowledges and skills. The distinction is straightforward: knowledges represent what a persona knows, while skills represent what she can do.
When creating something, a player will normally roll the persona’s knowledge, and keep the skill. The more you know about a field, the more likely you are to create something good, and the less likely you are to create something truly appalling. However, if you are lacking in skill, you will never do very well, while someone with great skill but poor knowledge might produce something great.
Knowledges are also used when checking to see whether the persona knows something, or understands the significance of something. In this case, the player rolls the knowledge, and keeps a number of dice based on the environment, and the hints that it gives towards the answer. A question with no context gives one die, and the difficulty to recall a fact is never higher than six. If a persona has studied a topic, there is a chance that she knows any fact, no matter how obscure. The difficulty to understand a situation may be higher, but as the situation itself provides more cues, the player also gets to keep more dice.
In principle, both knowledges and skills can be rolled or kept. Thus, there might be situations where a player rolls one knowledge and keeps another, or rolls one skill and keeps another. I suspect that rolling a skill and keeping a knowledge will be rare, but I don’t want to rule it out as a possibility. For example, there might be a skill “exam technique”, which personae roll when taking an examination, keeping the relevant knowledge. Given the topics of Kannagara, I think that rolling a knowledge and keeping a skill will be the most common situation.
In many cases, a knowledge and a skill might share a name. Thus, knowledge of norito and skill in composing norito would both be called “norito”. However, they should be written in different places on the persona sheet.
The issue here is ease of use. Having the same name for two abilities might be confusing, but calling them norito knowledge and norito skill is clumsy, and trying to come up with completely different names for every pair of abilities will become difficult, and lead to some strained terminology.
Abilities represent general ability, not particular facts a persona knows, nor particular techniques. Those would be represented by elements, at least in the creation process, and elements might well apply to single actions as well. Although someone with only one die in a knowledge has a one in six chance to know any general fact, some facts might be represented by elements, and unknown to any persona who does not have access to that element. Similarly, some techniques might be simply impossible if a persona does not have the relevant element to go with the skill.
The fundamental difference between the two types of ability not only affects how they are used in play, but also how they are improved. I suspect that I will not want to distinguish them during persona creation, but for later persona development the mechanisms will be different.