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Re: Categories and fixed="yes" James M Snell Mon Dec 24 06:02:24 2007

Comments below...

Joe Cheng wrote:
> As long as we're on the topic, can we try to get concrete
> about solving this for blogs at least? This is main obstacle
> to getting a good Blogging Profile spec and I'd really like to
> start building some momentum. So I'm just going to start
> thinking out loud.
> There's the notion of categories that almost every blogging
> platform supports (I've taken to calling these
> "blog-categories" to distinguish them from the too-generic
> concept used in Atom). And there's also tags, which are almost
> the same thing. I'm not sure the lines between the two terms
> are hard and fast; if anyone can educate me, please do.

There is a third form exemplified by systems like GData and Lotus
Connections: atom:categories used as flags.  For instance, GData and LC
both have the notion of a "type" category used to indicate the
application specific "type" of entry. LC goes a bit further and uses
certain atom:category schemes/terms to indicate whether an entry is
private or public, complete or incomplete, etc.  These schemes are fixed
and are distinctly unique in nature from atom:category elements used for
general categorization or folksonomy.  I have not seen them used
extensively in blogging applications, however (Lotus Connections blogs
is probably the only component in the suite that does not use the type
category, for instance)

> Most blogging platforms only support categories, not tags.
> Depending on the platform:
> * each post can have (zero or one), (exactly one), (zero or
>   more), or (one or more) categories assigned
> * the list of categories can be opened or fixed
> * categories can have distinct IDs (i.e. integer) or can be
>   identified solely by their term/label
> Some per-platform peculiarities:
> * WordPress allows categories to have hierarchy. Terms only
>   have to be unique among siblings. Each category has an ID
>   (auto-assigned by the server), term, slug, and parent.
>   WordPress tags are simply terms (no ID, slug, or parent),
>   and behave differently than categories in that clicking
>   on them will show posts from not only your blog but
>   other blogs as well.
> * Roller has two sets of categories: one predefined list that
>   is fixed, and one open list. I believe the former is
>   defined per server (where the server can have many blogs)
>   and the latter is maintained per blog.
> * Blogger has "labels" but these are blog-categories as far
>   as I can tell.

Although it's based on Roller, Lotus Connections Blogs only supports
tags.  The fixed category list has been disabled.

> If there are going to be multiple "schemes" (and you might
> consider categories and tags to be two different schemes)
> then there needs to be a way to provide a human-readable
> label for each scheme.

+1. I think is actually gets to the core of what is needed: a way of
defining and describing a scheme*.

> Given these requirements, can and should the solution be
> based on the categories currently defined in RFC5023?
> Might one approach be to try to come up with a blank-slate
> solution, and once we know exactly what that looks like,
> see whether it can be implemented using <categories> without
> losing too much?

I believe that it would help significantly if we can come up with a
reasonable approach to defining and describing a "scheme"


 <x:scheme ref="http://example.org" fixed="yes|no" label="Foo">
   <atom:category term="foo" />
   <atom:category term="bar" />

- James

* I know the RDF-folks in the audience probably just started twitching
like crazy :-)