Re: [Zope-dev] ZPatterns Image Archive Project

2001-04-02 Thread Phillip J. Eby

At 01:45 PM 4/1/01 -0700, Michael R. Bernstein wrote:

It seems as though the manage_upload method is supposed to
hand off the image data to RenderingKinds, which in turn
either replaces the image data in existing Renderings, or
creates new ones, by iterating through the rows in the
TinyTable.

[shudder].  No, not at *all*.  The calling pattern goes like this:

anArchiveImage.upload:
for kind in RenderingKinds.getKindsFor(self):
Renderings.setRenderingFor(self,kind,data)

The ArchiveImage is responsible for knowing the image data.  The
RenderingKinds specialist is responsible for knowing what renderings should
be made for an ArchiveImage.  The Renderings specialist is responsible for
creating and storing a rendering, given an image and a kind of rendering to
be made.  However, it may ask the kind object for dimensions or other
assistance in actually creating the rendering.  

Don't think "iterating through rows in the TinyTable".  Outside
RenderingKinds, nobody knows there's a TinyTable.  *You* don't know there's
a TinyTable, because the application integrator might decide to do it with
a table in an SQL database or a ZODB folder.

Don't think "RenderingKinds replaces the image data in existing
Renderings", because that's "meddleware" - objects meddling in each others'
business.  Renderings is responsible for renderings.  RenderingKinds is
only responsible for knowing about *kinds*.

This is probably the hardest part of ZPatterns design for people to learn.
Ironically, it's nothing more than the most fundamental of O-O design
principles.  Everybody thinks they know O-O, incredibly few do.  I was
doing O-O for almost *fifteen years* before I realized I wasn't even close
to doing it right at this level of design!


In turn, are RenderingKinds *also* responsible for returning
the appropriate Rendering based on a 'size' attribute? 

No.  RenderingKinds are responsible only for knowing about *kinds*, not the
details of a particular image.  Thus, it makes sense for RenderingKinds to
implement rules about what renderings an image *should* have, but the ones
it *does* have are the domain of the image itself (but delegated to the
Renderings specialist for actual implementation).


are ArchiveImages supposed to access Renderings directly to
find whatever Renderings exist for them?  Which SPecialist
now has a getRenderingFor(archiveImage,imageKind) method?

Renderings.  ArchiveImage should have getRendering(imageKind) which then
calls Renderings.getRenderingFor(self,imageKind).


I can also see a problem with the following situation: after
several Archive images are created along with their
appropriate Renderings, the configuration information in the
TinyTable is changed, with new sizes added, and existing
sizes deleted or edited.

I would not expect the entire image database to be resized
and new sizes created automatically, so the data in the
Renderings Specialist would be out of sync with the sizing
meta-data, with Renderings possibly 'orphaned', and other
Renderings 'missing'

I *think* that these problems can be avoided, if the
Renderings Specialist is still responsible for reporting
what Renderings an ArchiveImage *has* (and possibly what
their dimensions are), and the RenderingKinds Specialist is

responsible for removing orphan renderings and creating
missing Renderings when the Image is either uploaded again
or 'refreshed'.

How would you reccomend handling this?

That depends on what the requirements are.  If you need to implement this,
then the sensible place to do it is probably in the RenderingKind objects
and RenderingKinds specialist.  That is, adding a RenderingKind might
include the option to go through and create the missing renderings, and
deleting or altering one might similarly prompt for updates.


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Re: [Zope-dev] ZPatterns Image Archive Project

2001-04-02 Thread Michael R. Bernstein

"Phillip J. Eby" wrote:
 
 At 05:08 PM 4/1/01 -0700, Michael R. Bernstein wrote:
 
 I'm also assuming that RenderingKinds' defaultRack is set to
 use 'ZPatterns: DataSkin' and be set to load by accessing
 the 'id' attribute. Is this correct?
 
 Well, I would create a "RenderingKind" ZClass, so as to be able to give it
 methods and to be able to distribute the class as part of the framework.

Is that strictly neccessary, or can I just have a few Python
Scripts in the RenderingKind specialist? Won't those work
just as well?

BTW, I thought that with the setup I described, I should be
able to access the settings data through the web, ie:

http://myserver.com/ArchiveImages/RenderingKinds/thumbnail/

where RenderingKinds has an index_html has a dtml-var
maxdimension in it. But this fails, and reports a
non-existent variable 'maxdimension'.

Obviously I'm doing something wrong, but I don't know what.

Michael Bernstein.

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Re: [Zope-dev] ZPatterns Image Archive Project

2001-04-02 Thread Michael R. Bernstein

"Phillip J. Eby" wrote:
 
 At 01:45 PM 4/1/01 -0700, Michael R. Bernstein wrote:
 
 It seems as though the manage_upload method is supposed to
 hand off the image data to RenderingKinds, which in turn
 either replaces the image data in existing Renderings, or
 creates new ones, by iterating through the rows in the
 TinyTable.
 
 [shudder].  No, not at *all*.  The calling pattern goes like this:
 
 anArchiveImage.upload:
 for kind in RenderingKinds.getKindsFor(self):
 Renderings.setRenderingFor(self,kind,data)
 
 The ArchiveImage is responsible for knowing the image data.  The
 RenderingKinds specialist is responsible for knowing what renderings should
 be made for an ArchiveImage.  The Renderings specialist is responsible for
 creating and storing a rendering, given an image and a kind of rendering to
 be made.  However, it may ask the kind object for dimensions or other
 assistance in actually creating the rendering.
 [snip]
 Don't think "RenderingKinds replaces the image data in existing
 Renderings", because that's "meddleware" - objects meddling in each others'
 business.  Renderings is responsible for renderings.  RenderingKinds is
 only responsible for knowing about *kinds*.

Ok. RenderingKinds (in my implementation) iterates through
the TinyTable, and returns a list of Kind objects.

Then, the ArchiveImage sends the list of Kinds to
Renderings. Renderings, in turn, iterates through the list
(grabbing dimension info from the Kind object) and creates
each Rendering appropriately.

 In turn, are RenderingKinds *also* responsible for returning
 the appropriate Rendering based on a 'size' attribute?
 
 No.  RenderingKinds are responsible only for knowing about *kinds*, not the
 details of a particular image.  Thus, it makes sense for RenderingKinds to
 implement rules about what renderings an image *should* have, but the ones
 it *does* have are the domain of the image itself (but delegated to the
 Renderings specialist for actual implementation).

Ok.

 are ArchiveImages supposed to access Renderings directly to
 find whatever Renderings exist for them?  Which Specialist
 now has a getRenderingFor(archiveImage,imageKind) method?
 
 Renderings.  ArchiveImage should have getRendering(imageKind) which then
 calls Renderings.getRenderingFor(self,imageKind).

Mmm. I think I see, but you didn't actually answer the first
of the two questions. More below.

 I can also see a problem with the following situation: after
 several Archive images are created along with their
 appropriate Renderings, the configuration information in the
 TinyTable is changed, with new sizes added, and existing
 sizes deleted or edited.
 
 I would not expect the entire image database to be resized
 and new sizes created automatically, so the data in the
 Renderings Specialist would be out of sync with the sizing
 meta-data, with Renderings possibly 'orphaned', and other
 Renderings 'missing'
 
 I *think* that these problems can be avoided, if the
 Renderings Specialist is still responsible for reporting
 what Renderings an ArchiveImage *has* (and possibly what
 their dimensions are), and the RenderingKinds Specialist is

Here's what I meant:

Should ArchiveImage have a getRenderings(self) which in turn
calls Renderings.getRenderingsFor(self)? This should (I
think) return a list of Kinds that Renderings has stored for
a particular ArchiveImage.

 responsible for removing orphan renderings and creating
 missing Renderings when the Image is either uploaded again
 or 'refreshed'.
 
 How would you reccomend handling this?
 
 That depends on what the requirements are.  If you need to implement this,
 then the sensible place to do it is probably in the RenderingKind objects
 and RenderingKinds specialist.  That is, adding a RenderingKind might
 include the option to go through and create the missing renderings, and
 deleting or altering one might similarly prompt for updates.

Um. You mean for all ArchiveImages? What I meant is that you
would be able to tell an individual ArchiveImage to either
upload new data or just 'refresh' itself (manually), and a
process substantially similar to the ArchiveImage creation
process would create missing Renderings, and overwrite the
ones that already existed (just in case their dimensions
changed), and delete Renderings that no longer had an
equivalent RenderingKind. All for the individual image, not
for all images.

I can later add a batch interface to trigger this on X
images at a time, to avoid causing the server to thrash.

Does this seem reasonable?

Thanks for the help,

Michael Bernstein.

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Re: [Zope-dev] ZPatterns Image Archive Project

2001-04-01 Thread Phillip J. Eby

At 08:59 PM 3/30/01 -0800, Michael R. Bernstein wrote:
"Phillip J. Eby" wrote:
 
 Aha.  I think I understand what you're doing now.  You have an "Image" and
 you have a "Rendering".  Two classes, different behaviors.  I'm assuming
 that originals and thumbnails and whatever other renderings exist have no
 real behavioral differences and can be implemented with the same class and
 storage characteristics.

The terminology I'm using is ArchiveImage (for the 'Image'
class) and RackImage (for the 'Rendering' class).

I'd recommend a name change for RackImage, at least at the Specialist
level.  If you don't like Renderings, then maybe RenderedImages,
ActualImages, or some such.  Specialist names should reflect the *purpose*
of a thing in the application rather than the nature of the thing itself.


I think that different sizes would have the same behavioural
characteristics (simply an image file, really), but am less
sure about storage. My application will attempt to store all
the renderings in the ZODB, but if I want this to be
reusable, I have to assume that someone (including me) might
want to store the image data on the FS instead. If it's
going to be stored on the FS, it would be natural to dump
different sizes into separate directories, or even separate
partitions. Two years from now, this web application could
contain around 300 Gb of images (current prices on that much
storage are about $1,000 for ten 30 Gb hard-drives, so I'm
not too worried on that score).

This can still be accomplished with a single specialist, if your 'id'
format contains the necessary information to distinguish between image
sizes/types.  If a user of your framework wants to seperate the storage,
they can create more than one rack and have the specialist distinguish
between them using the contents of the 'id'.  It's best to keep
implementation simple in the reference implementation of a framework.


 That's what I meant, sorry. The RackImages need to appear to
 be attributes of the ZClass, and I'll use SkinScripts to
 accomplish that.
 
 That's really only practical if you have a fixed set of rendering types and
 names, but it'll work for retrieval.  It won't really help you with
 creation and assignment, though.  I'd suggest specialized methods on Image
 which delegate to the Renderings specialist.

I was thinking of a manage_upload method on the
ArchiveImage, that iterated through a list of sizes and used
an external method that imports PIL to resize the image
data, then passes the resized image data into the RackImage
manage_upload method.

Does that seem reasonable?

It seems to me that sizing renderings should be the responsibility of the
Renderings specialist.  That is, the ArchiveImage upload method would look
something like this:

for imageKind in ('fullsize','thumbnail'):
Renderings.setRenderingFor(self,imageKind,imageData)


The setRenderingFor method would take the ArchiveImage's id, tack the
imagekind onto it, and either retrieve the current image or create a new
one, then re-size the image according to your rules for what size fullsize
or thumbnail is, and pass it to the current or new rendered image object.
(A counterpart method, getRenderingFor(archiveImage,imageKind) would do a
similar id transformation to retrieve a rendering when called by the
ArchiveImage's getRendering() method.)


Of course, this means that the Renderings specialist has to know what
sizes different size names mean, and that ArchiveImages have to know the
possible sizes.  Such knowledge being spread across two specialists means
there's a specialist missing: RenderingKinds.  This may be a sub-specialist
of Renderings, or a peer of Renderings within ArchiveImages.  If a
sub-specialist of Renderings, Renderings must expose a method to retrieve
the sizes, and the upload method above would look like this instead:

for imageKind in Renderings.getRenderingKindsFor(self):
Renderings.setRenderingFor(self,imageKind,imageData)

Although, it may be in your framework that ArchiveImages are responsible
for knowing which kinds of renderings they should have, and the
RenderingKinds specialist will simply deal with implementation details such
as how each kind is sized and which rack they're stored in within the
Renderings specialist.

By the way, RenderingKinds is a sort of specialist that hasn't been
discussed much outside of the apps Ty and I work with - the "constant"
Specialist, one which contains application configuration or metadata rather
than "content".  Oftentimes it's handy to simply base a Specialist on a
TinyTable or similar product in order to set up configuration of constant
items like RenderingKinds.  Consider the TinyTable data below:

Columns: name:string scaling:float width:int height:int rackname:string

"fullsize",1.0,0,0,"bigimages"
"halfsize",0.5,0,0,"bigimages"
"thumbnail",0.0,64,64,"thumbnails"

The RenderingKinds specialist would have a single rack, which uses
SkinScript to pull in the data from the TinyTable (WITH

Re: [Zope-dev] ZPatterns Image Archive Project

2001-04-01 Thread Michael R. Bernstein

"Phillip J. Eby" wrote:
 
 At 08:59 PM 3/30/01 -0800, Michael R. Bernstein wrote:
 
 The terminology I'm using is ArchiveImage (for the 'Image'
 class) and RackImage (for the 'Rendering' class).
 
 I'd recommend a name change for RackImage, at least at the Specialist
 level.  If you don't like Renderings, then maybe RenderedImages,
 ActualImages, or some such.  Specialist names should reflect the *purpose*
 of a thing in the application rather than the nature of the thing itself.

Ah. That makes sense. Ok, so now my RackImage class is being
stored in a defaultRack of a Renderings Specialist contain
within the main ArchiveImages Specialist.

 I think that different sizes would have the same behavioural
 characteristics (simply an image file, really), but am less
 sure about storage. My application will attempt to store all
 the renderings in the ZODB, but if I want this to be
 reusable, I have to assume that someone (including me) might
 want to store the image data on the FS instead. If it's
 going to be stored on the FS, it would be natural to dump
 different sizes into separate directories, or even separate
 partitions.
 
 This can still be accomplished with a single specialist, if your 'id'
 format contains the necessary information to distinguish between image
 sizes/types.  If a user of your framework wants to seperate the storage,
 they can create more than one rack and have the specialist distinguish
 between them using the contents of the 'id'.  It's best to keep
 implementation simple in the reference implementation of a framework.

Ok.

 I was thinking of a manage_upload method on the
 ArchiveImage, that iterated through a list of sizes and used
 an external method that imports PIL to resize the image
 data, then passes the resized image data into the RackImage
 manage_upload method.
 
 Does that seem reasonable?
 
 It seems to me that sizing renderings should be the responsibility of the
 Renderings specialist.  That is, the ArchiveImage upload method would look
 something like this:
 
 for imageKind in ('fullsize','thumbnail'):
 Renderings.setRenderingFor(self,imageKind,imageData)
 
 The setRenderingFor method would take the ArchiveImage's id, tack the
 imagekind onto it, and either retrieve the current image or create a new
 one, then re-size the image according to your rules for what size fullsize
 or thumbnail is, and pass it to the current or new rendered image object.
 (A counterpart method, getRenderingFor(archiveImage,imageKind) would do a
 similar id transformation to retrieve a rendering when called by the
 ArchiveImage's getRendering() method.)
 
 Of course, this means that the Renderings specialist has to know what
 sizes different size names mean, and that ArchiveImages have to know the
 possible sizes.  Such knowledge being spread across two specialists means
 there's a specialist missing: RenderingKinds.

 [snip RenderingKinds as a sub-specialist of Renderings]
 
 Although, it may be in your framework that ArchiveImages are responsible
 for knowing which kinds of renderings they should have, and the
 RenderingKinds specialist will simply deal with implementation details such
 as how each kind is sized and which rack they're stored in within the
 Renderings specialist.
 
 By the way, RenderingKinds is a sort of specialist that hasn't been
 discussed much outside of the apps Ty and I work with - the "constant"
 Specialist, one which contains application configuration or metadata rather
 than "content".  Oftentimes it's handy to simply base a Specialist on a
 TinyTable or similar product in order to set up configuration of constant
 items like RenderingKinds.
 [snip]
 Now, you could make a RenderingKind class that uses this data to resize an
 image.  That is RenderingKind would have a sizeImage(imageData) method that
 returned a new image of the appropriate size.  It could also have a
 rackname attribute which would tell the Renderings specialist which rack an
 image of that kind should be stored in.  The user of the application could
 reconfigure at will by changing the contents of the TinyTable.
 
 This might be all that RenderingKind objects do in the application - resize
 images and say where to put them.  But over time, you might find additional
 uses for them.  Like for example if you had certain rules about which kinds
 of renderings should be created for certain types of ArchiveImages.

Ok, using a RenderingKinds does seem like the way to go
here, since I eventually want renderings to be created using
different file formats (gif, jpeg) based on whether the
image is color or bw (set as a property on ArchiveImage).

But I'm confused a bit:

It seems as though the manage_upload method is supposed to
hand off the image data to RenderingKinds, which in turn
either replaces the image data in existing Renderings, or
creates new ones, by iterating through the rows in the
TinyTable.

In turn, are RenderingKinds *also* responsible for returning
the appropriate Rendering based on 

Re: [Zope-dev] ZPatterns Image Archive Project

2001-04-01 Thread Michael R. Bernstein

"Phillip J. Eby" wrote:
 
 By the way, RenderingKinds is a sort of specialist that hasn't been
 discussed much outside of the apps Ty and I work with - the "constant"
 Specialist, one which contains application configuration or metadata rather
 than "content".  Oftentimes it's handy to simply base a Specialist on a
 TinyTable or similar product in order to set up configuration of constant
 items like RenderingKinds.  Consider the TinyTable data below:
 
 Columns: name:string scaling:float width:int height:int rackname:string
 
 "fullsize",1.0,0,0,"bigimages"
 "halfsize",0.5,0,0,"bigimages"
 "thumbnail",0.0,64,64,"thumbnails"

In my application, I'm only interested in specifying the
'maximum dimension' in any direction. This seems to work
better generally, because it accounts automatically for
images that are landscape or portrait oriented. So my
TinyTable only has two columns:

Columns: name:string maxdimension:int

 The RenderingKinds specialist would have a single rack, which uses
 SkinScript to pull in the data from the TinyTable (WITH
 theTinyTable[self.id] COMPUTE scaling,width,height,rackname).

The SkinScript (which I placed in the RenderingKinds
Specialist, not in it's defaultRack) has the following line
in it:

WITH sizes[self.id] COMPUTE maxdimension

I eliminated the 'rackname' column, because you reccomended
that all Renderings(RackImages) be stored in the same Rack,
for simplicity. This also seems the more flexible approach
(ie. I don't have to create management screens to add and
delete racks when the sizes change), so there is less
'hardwiring'.

Now, am I correct in assuming that the 'sizes' TinyTable
should be in the RenderingKinds Specialist?

I'm also assuming that RenderingKinds' defaultRack is set to
use 'ZPatterns: DataSkin' and be set to load by accessing
the 'id' attribute. Is this correct?

Thanks,

Michael Bernstein.

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Re: [Zope-dev] ZPatterns Image Archive Project

2001-03-30 Thread Phillip J. Eby

At 05:27 PM 3/30/01 -0800, Michael R. Bernstein wrote:
Now I am working on a ArchiveImage ZClass that holds 'meta'
information about an image, such as the description, a date,
and keywords.

I want to have one Rack for each image size that I want to
store.

Just out of curiousity, why do you want seperate racks for each size?  Are
they being stored in different ways or have different behavioral
requirements (e.g. different classes) apart from their size?  If not, there
is probably no reason to have multiple racks.


I realize that I need to tie the Racks together in the
specialist using SkinScripts

SkinScript doesn't do anything to tie racks together or to a Specialist -
it's just a way of describing where the data comes from/goes to for a
particular Rack.


Where do I put the separate Racks? do I create a specialist
for each Rack (seems unneccessary) or do I put several Racks
in the same Specialist?

Several in the same, if they are providing objects which fill the same role
in your overall application.


If the latter, I'm unsure how to use DTML or PythonScripts
to specify which Rack to create a new item in.

The DTML I am using to instantiate RackImages in the Rack
for example, is as follows:

dtml-let ni="newItem(REQUEST.id)"
 dtml-call "ni.manage_edit(REQUEST.title,'')"
 dtml-call "ni.manage_upload(REQUEST.file)"
/dtml-let

But this code only works for a Rack named defaultRack, which
I can obviously only have one of.

Any advice on this would be greatly appreciated.


Just use the name of the rack, e.g.:

dtml-let ni="rackOne.newItem(REQUEST.id)", etc.

Racks are subobjects of their specialists.


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Re: [Zope-dev] ZPatterns Image Archive Project

2001-03-30 Thread Michael R. Bernstein

"Phillip J. Eby" wrote:
 
 At 05:27 PM 3/30/01 -0800, Michael R. Bernstein wrote:
 Now I am working on a ArchiveImage ZClass that holds 'meta'
 information about an image, such as the description, a date,
 and keywords.
 
 I want to have one Rack for each image size that I want to
 store.
 
 Just out of curiousity, why do you want seperate racks for each size?  Are
 they being stored in different ways or have different behavioral
 requirements (e.g. different classes) apart from their size?  If not, there
 is probably no reason to have multiple racks.

Well, I want to store several versions of each image. Let's
take a simplified case where I want the original image and a
thumbnail, both of which need to appear as subobjects of the
ZClass with the meta-data.

If I store all the RackImages (originals and thumbnails) in
one Rack, how do I differentiate between them, so that
'/Archive/001/thumbnail' and 'Archive/001/original' show the
appropriate images? It just seemed simpler to create a
'thumbnail' Rack and an 'original' Rack.

 I realize that I need to tie the Racks together in the
 specialist using SkinScripts
 
 SkinScript doesn't do anything to tie racks together or to a Specialist -
 it's just a way of describing where the data comes from/goes to for a
 particular Rack.

That's what I meant, sorry. The RackImages need to appear to
be attributes of the ZClass, and I'll use SkinScripts to
accomplish that.

 Where do I put the separate Racks? do I create a specialist
 for each Rack (seems unneccessary) or do I put several Racks
 in the same Specialist?
 
 Several in the same, if they are providing objects which fill the same role
 in your overall application.

And do the RackImages Racks go into the same Specialist as
the ZClass Rack?

 The DTML I am using to instantiate RackImages in the Rack
 for example, is as follows:
 
 dtml-let ni="newItem(REQUEST.id)"
  dtml-call "ni.manage_edit(REQUEST.title,'')"
  dtml-call "ni.manage_upload(REQUEST.file)"
 /dtml-let
 
 But this code only works for a Rack named defaultRack, which
 I can obviously only have one of.
 
 Just use the name of the rack, e.g.:
 
 dtml-let ni="rackOne.newItem(REQUEST.id)", etc.

Ok, thanks! That works (Duh).

Michael Bernstein.

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Re: [Zope-dev] ZPatterns Image Archive Project

2001-03-30 Thread Phillip J. Eby

At 07:30 PM 3/30/01 -0800, Michael R. Bernstein wrote:
"Phillip J. Eby" wrote:
 
 At 05:27 PM 3/30/01 -0800, Michael R. Bernstein wrote:
 Now I am working on a ArchiveImage ZClass that holds 'meta'
 information about an image, such as the description, a date,
 and keywords.
 
 I want to have one Rack for each image size that I want to
 store.
 
 Just out of curiousity, why do you want seperate racks for each size?  Are
 they being stored in different ways or have different behavioral
 requirements (e.g. different classes) apart from their size?  If not, there
 is probably no reason to have multiple racks.

Well, I want to store several versions of each image. Let's
take a simplified case where I want the original image and a
thumbnail, both of which need to appear as subobjects of the
ZClass with the meta-data.

Aha.  I think I understand what you're doing now.  You have an "Image" and
you have a "Rendering".  Two classes, different behaviors.  I'm assuming
that originals and thumbnails and whatever other renderings exist have no
real behavioral differences and can be implemented with the same class and
storage characteristics.


If I store all the RackImages (originals and thumbnails) in
one Rack, how do I differentiate between them, so that
'/Archive/001/thumbnail' and 'Archive/001/original' show the
appropriate images? It just seemed simpler to create a
'thumbnail' Rack and an 'original' Rack.

It sounds to me like you want an Images specialist and a Renderings
specialist, with the latter contained within the former (because Renderings
are only accessed by way of Images).  Your Image class should have a
"getRendering(kind)" method which accesses the renderings specialist to
retrieve a rendering, and it can also have a __bobo_traverse__ method that
uses getRendering to allow traversal as you describe.  This would still be
completely storage independent, since that's hidden in the Renderings
specialist.  Likewise, when your Images create renderings, they'll need to
delegate the actual creation to the Renderings specialist.

If you need different classes for different kinds of renderings, you'll
need multiple racks inside the Renderings specialist, but if renderings are
basically just a Zope Image object, you can just use a single Rack (and
make your id values something like '001_original', '002_thumbnail', etc.
and construct these in your getRendering() method).


That's what I meant, sorry. The RackImages need to appear to
be attributes of the ZClass, and I'll use SkinScripts to
accomplish that.

That's really only practical if you have a fixed set of rendering types and
names, but it'll work for retrieval.  It won't really help you with
creation and assignment, though.  I'd suggest specialized methods on Image
which delegate to the Renderings specialist.


 Where do I put the separate Racks? do I create a specialist
 for each Rack (seems unneccessary) or do I put several Racks
 in the same Specialist?
 
 Several in the same, if they are providing objects which fill the same role
 in your overall application.

And do the RackImages Racks go into the same Specialist as
the ZClass Rack?

Sorry, I didn't realize you had two different notions - the abstract notion
of an Image and the concrete notion of its Rendering.  So there are two
specialists, and (at least) two racks.


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