[mythtv] What is an "episode" ? What is a "part" ?

[Håkon Alstadheim]

I find I confuse myself more on this question the more I think about 
this. I get shows with descriptions like "(2:3)" , "(2:3/s4)" or 
"(2/s4)". I've also seen "Sesong 4. (2) ", indicating episode 2, total 
number of episodes 3, and season 4 in those examples. Other variations 
also exist. This system is fairly new in my part of the world, so I have 
never seen how "part 2 of episode2" would be marked.

My question is: should I use the above strings from the description to 
fill in "syndicatedepisodenumber" AND also partnumber and parttotal ?
Why is one a string and the others integers ?
What would it take to change myth into storing episodes, parts, seasons 
and total episodes in a consistent way? -- That is, how is this 
information used by myth ?