Chris Withers wrote:
'DataSkins' doesn't mean a lot to me as a name :S What components would go into this product?
An object that has DataSkin as a base class allows a DataManager to look after its data storage requirements. The DataManager stores all the propertysheets and attributes, and works out what to do and who to notify when things change. There are various types of DataManager in ZPatterns, and the important ones take plug-ins so that you can greatly modify their behaviour. Specialists and Customizers (aka Folders w/ customizer support) are the main DataManagers you build an application out of. Specialists may have Racks inside them to actually do the work of storing the data, so you can think about your application's architecture at many different levels of abstraction. You can say "The AddressBook specialist manages Address DataSkins" but you can also say "The Addresses rack in the AddessBook specialist stores the Address DataSkins". When Objects get created or deleted or changed, a DataManager will tell any Agents it knows about that this has happened, in case they are interested. An Agent is anything that monitors the events produced when things happen to DataSkins. A Trigger is a kind of Agent that does something concrete, like calling a method, in response to a change in a DataSkin. You can use a Trigger to update a ZCatalog when a DataSkin gets added or deleted or changes. This is good because catalog-awareness gets to move out of the domain objects (business objects, or whatever) and into the parts of your system that are concerned with the management of those objects. You can even use two Triggers to update two different Catalogs when a DataSkin changes -- for example, the AddressBook catalog, and also a SiteIndex catalog for searching all the data in your system. Perhaps the SiteIndex holds just minimal indexes and meta-data, whereas the AddressBook catalog holds meta-data and indexes more specialised to an address book. Two other important aspects of the DataSkins part of ZPatterns are SheetProviders and AttributeProviders. These plug into Racks (and anything else that takes "Data Plugins") and do the work of getting propertysheets and calculating or importing attributes. These attributes and propertysheets generally end up as the data belonging to the DataSkins.
Yup, sounds like a great idea. Hopefulyl Pluggins could get into the Zope core ASAP. I reckon they might be quite useful to ZMI mark II :-)
What is ZMI? -- Steve Alexander Software Engineer Cat-Box limited http://www.cat-box.net