[p2-dev] Categories

[Thomas Hallgren <thomas@xxxxxxx>]

Hi,
I discovered that an attempt to install from a MetadataRepository that 
contains only features and bundles will not work. The UM will not 
display IU's unless they are found below a category. This seems to be 
true regardless of if I list by category or not (I'm using the 3.5 
integration build from 22/1). I would expect uncategorized IU's to at 
least show up under 'Uncategorized'.

The current use of categories as IU's is of some concern to me. I can 
see several cons with that approach:

1. Categories in general are not using qualified names and this results 
in collisions when aggregating repositories. We often see categories 
named 'core', 'optional', 'tools' etc.

2. Categories are not versioned so we cannot really track how they 
change over time.

3. Inviting users to install a category is often counter intuitive. They 
may contain several mutually exclusive choices (Subclipse and Subversive 
in the SVN category for instance) or a bunch of features listed under 
"Optional". You're not supposed to install "Optional". The idea is that 
you make your own pick from that category.

4. Categorization would make a lot of sense if you (the IU publisher) 
were able to hook into well known categories when publishing. As it is 
now, you must own the category and the only thing it can contain is 
listed in its required capabilities, essentially making the category 
useless (and occupied) for everyone else. I think that category affinity 
should be a provided capability (or property) in the respective IU's 
that "belongs" to the category. Having the category itself list its 
content as requirements is doing it backwards.

Regards,
Thomas Hallgren