[Zope-dev] ZPatterns design questions

[Phillip J. Eby]

At 01:49 PM 10/3/00 -0700, John Eikenberry wrote:
>
>First, some context... I'm working on a new data storage system for a
>related set of (primarily) Zope sites. The data will be kept in ZODB and
>mirrored out to a RDB (MySQL) to provide read-only access to some non-zope
>stuff. One other thing to note, all of this will be done via python code
>(no zclasses).
>
>Now say that I want to keep data about a company. I have a specialist, rack
>and dataskin already created. I currently can store data on the skin via
>AttributeProviders, but this was mainly done to get something working to
>mess around with. 
>
>What I think I want is several SheetProviders. Two for each block of data
>(a block basically reflect the breakdown of tables in the MySQL DB). Why 2
>for each block, one for the ZODB store and one for mirroring the data out
>to the RDB. So, the breakdown for the company would look like this:
>
>Company Rack
>  - Company Information (name, url, etc). 
>    . SheetProvider (ZODB) - read/write
>    . SheetProvider (SQL) - write only
>  - Address Information (city, state, zip, etc)
>    . SheetProvider (ZODB) - read/write
>    . SheetProvider (SQL) - write only
>
>Does this sound reasonable? I thought about writing a mix-in class to add
>the SQL stuff to the SheetProvider, eliminating the need for 2 entries for
>each block of data. But I liked the idea of each being its own plugin,
>seemed cleaner.

If I can offer a suggestion...  It sounds to me like you don't need
SheetProviders at all, if you effectively define the property sheets as
part of your class, and make the attributes direct attributes on the
DataSkin.  You then need only set up a single trigger that checks whether
any of the attributes you want to mirror have changed, and then fires that
off to the SQL db.  It would actually be a bit easier to set up if you were
using a ZClass, since you could create the property sheets there by just
adding "DataSkin Property Sheet" objects to the ZClass.  But the basic
principle would still apply.