Hi Chuck, Thanks for your input and I hope it will help me understand the EOF relationship modelling better. Comments below:
On 2010-11-07, at 8:35 PM, Chuck Hill wrote: > On Nov 6, 2010, at 11:02 PM, Farrukh Ijaz wrote: > >>> For your case, I'm finding it difficult to imagine why two entities >>> (IS-A) have such different relationship requirements. >> >> The model has a legacy. In the beginning the entities appear to be different >> but semantically they are have some common behaviour when observed under >> specific domain . E.g. in a File System we have File and Folder (Directory) >> two separate entities. But at OS level, both have name, timestamp, >> permissions etc. The need before was to treat File and Folder as separate >> entities, but now the requirement demands to have some granularity among >> them. This is just an example to explain the situation. > > > But do they share behavior? Shared data is not necessarily an indication for > inheritance. I can't answer this with 100% accuracy. But let me try to explain the model using Unix file system so it could become clear whether they share behaviour or not. In Unix (or Linux) I can create directories (Entity A), and files (Entity B). Directories can have subdirectories and files (Entity A -> toMany Entity A and Entity A -> toMany Entity B). Now I have a requirement where I need to have a special type of directory (Entity C) which can have symlinks (Entity D) or subdirectories of it's own type (Entity C) which means Entity C -> toMany Entity C and Entity C -> toMany Entity D. Each symlink can only point to directory, file, special directory or another symlink (which means Entity D -> toOne Entity A or toOne Entity B or toOne Entity C or toOne Entity D). In this situation, if need an abstraction (either based on java based interface or EOF inheritance) which could treat all Entity A, Entity B, Entity C and Entity D such as Entity Alpha so I could have only 1 toOne relationship from Entity D to Entity Alpha. My assumption is, if I implement a Java interface instead of EOF inheritance, EOF won't help much and I need to manage this relationship programmatically, right? If the explanation is still confusing then I would opt for four toOne relationships from Entity D -> Entity A, Entity B, Entity C and Entity D. Assign all of them an interface to collect common data provide additional method to return a common object (by inspecting all of the four relationships as only 1 will be present at a time). Farrukh _______________________________________________ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
