[Grok-dev] Problem with Annotations

Sebastian Ware sebastian at urbantalk.se
Wed Sep 23 06:58:09 EDT 2009

Personally I would probably have one Annotation class that handles all  
the meta data. I would define a view (orinary or JSON) to access the  
meta data (rather than using traverse).


For simple meta data you might want to store them in a PersistentDict  
in order to avoid multiple db-lookups. If the meta data is large, you  
will want a BTree-style container (such as grok.Container).

Mvh Sebastian

On 23 sep 2009, at 12.15, Paul Wilson wrote:

> Hi there,
> I've been having difficulty thinking this one through, any hints  
> appreciated.
> I'm writing a hobby framework (and content management system) with
> Grok. The content will have meta-data associated with it. Naturally,
> I've decided to use annotations to model this meta data. I don't know
> what meta data will be stored up front; opting instead to allow such a
> facility to be plugged in. Let's say a have an object called 'foo'
> that is found at location:
> http://localhost/container/foo
> A plugin may, for example, define an IMetaData interface and MetaData
> annotation that stores the X and Y coordinate of foo. When a client
> accesses the metadata, it is the interface's schema that is used to
> deserialise it. So, what I need is some URL format or mechanism that
> allows me to reference an interface so that I can adapt the content
> object to it and retrieve the object and then go on to deserialise it.
> So the first question is, is there some way to look up (in the ZCA) an
> interface by name? This would allow:
> http://localhost/container/foo/_metadata
> I would then go on to define a grok.Traverser that strips the leading
> slash and looks up the interface.
> My second question is related. Is there a way to avoid having this
> naming convention of the leading underscore or similar. Views have @@,
> and layers have ++Layer++, is there some way of doing something
> similar in grok to say 'this is not an object, please treat it
> differently'?
> Thanks in advance.
> Regards,
> Paul
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