I've re-read this thread and still not sure of the problem/goal of of this thread to only record "new" shows.
From a USA point of view if the "new" flag shown in the zap2it tvlistings meets your needs you can use xmltv with mc2xml and the "-a" or "-b" command line option to only record "new" shows. This adds a " *" to the Title of either "new" or "NOT(new)" shows. MePo can use this when recording shows so it only records shows that zap2it flags as "new" . I think this would meet the needs of Anthyony who started this thread and Pat/Carl.
If you can't use mc2xml to get the "new" info, or want a way to track/skip shows you've already recorded, I guess that would need a new or enhanced plugin that uses parts of Trakt, TV WishList, and TV Series to track already recorded shows, find new shows, and generate recording requests that are sent to the TV Server.
I think this whole issue is being over thinked. MCE always had an option to only record new shows based upon the "new" indicator in the EPG which flagged the first airing of a show in general. This is what most users would consider a new airing. I think it would make sense to at least add this feature as an option in the configuration and then have some parameters which would allow the user to configure how it is flagged in the database.
Just tried something that works great for me.. I ran the mc2xml with the -a option and it added the * to the EPG show name if it was a "new" airing. Then since the recording schedule is based upon the name I was able to set it up to record the shows I want with the * in the name field so now it only records new shows.
gwatkins, glad you were able to get your recordings set up the way you wanted. My previous post was an attempt to explain the options using mc2xml/xmltv. I actually use the -b option so I could continue using my existing scheduled recordings. A few shows like local TV news always show up a "old" so I needed to tweak a few recordings.
Another attempt to outline USA specific steps to flag old/new episodes. This assumes you want use mc2xml for EPG data.
2A. To mark all "new episodes" with a "*" use the following for mc2xml
mc2xml.exe -a -o tvguide.xml
with this option the show titles will be either of the following and you can select if you record old or new episodes
How I Met Your Mother * (New Episodes)
How I Met Your Mother (Old Episodes)
2B. To mark all "old episodes" with a "*" use the following for mc2xml
mc2xml.exe -b -o tvguide.xml
with this option the show titles will be either
How I Met Your Mother * (Old Episodes)
How I Met Your Mother (New Episodes)
MePo "Recorded TV" will show the actual Title used for the recording with or without the "*". The TV Series plugin ignores the "*" and all "old" or "new" episodes will be grouped together.