Well, I'm pretty new to XML and haven't really done much research on it, so I can't help you with websites or books. But if you want my rather uninformed opinion anyway, I like the first construct best.
<action scope="global">
blah ..
</action>
As long as a given action can have only one scope, and that scope can be represented by a simple
string, this is all you need IMO. And all the "blah..." is clearly modified by the scope "global".
<action>
<scope>global</scope>
blah ..
</action>
This one could be useful if your concept of scope is more complex - e.g. if you want to define the scope to include modules A and C, but not B:
<action>
<scope>module A</scope>
<scope>module C</scope>
blah ..
</action>
But this is longer obviously. And it's not as obvious to me whether "blah..." is modified by one, both, or neither of the scope elements. It looks like "blah..." is outside the scope of either <scope>. Maybe there's a way in XML to specify whether this is the case or not; I dunno.
<action>
<scope>global</scope>
<content>
blah ..
</content>
</action>
Again, is the content modified by the scope? It doesn't look like it, IMO. Do you want to be able to have more than one <content> as well as more than one <scope> inside an <action>? If not, this seems like overkill. Also, I tend to think that the "content" of the <action> is already implicitly (or explicitly?) defined as whatever is in between the <action ...> and the </action>.
<global-action>
blah ..
</global-action>
This could work. But will there be other types of actions, e.g. <local-action>? Will they be similar in most ways? I'd want to keep their common behavior in a single <action> element. But that's my OO thinking - I'm not sure how necessary it really is here.
