There might be many ways to implement each connection, but I think that there will always be one or two ways that would be simplest and most robust... so this would not only save you the trouble of figuring it out alone every time, but would also prevent you from getting stuck down the road. The problem is that we have at best guesses, and at worst empty table cells in the guide. I'm still struggling with many of these... The worst one seems to be XOR type connections, where a Specialist implementing a role is not involved. Example: Actor: Person. Participants: Customer, Reseller Object connections: (Customer) 1-------[XOR A] 1 (Actor) [XOR A] 1-------1 (Reseller) acl_users Login Manager authenticates users using Actor objects (by connecting the the Actors Specialist). The application needs to identify the Participant. If you add participant_id to Actor, you still don't know which Participant Specialist to load the Participant from. You don't want to add participant_type to Actor (at least, I don't think you do - it seems real ugly). So, what do you do? Do you place the Customers and Resellers Specialists inside a Participants Specialist? We'll have to call it MegaSpecialist :-). Bad idea - other parts of the application have to access Resellers specifically, so Resellers should not be hidden inside the MegaSpecialist. So, do you create a Participants Specialist with virtual Racks for Customers and Resellers? What, another Specialist just to link Actors to Participants? Will this never end :-(? See, I'm stuck. Please please please could someone who do not identify themselves as ZPatterns novices find the time to add to this guide? Steve Spicklemire wrote:
I think this is a brilliant idea! I'm sure there are sixteen ways to implement each of these... but having one concrete way would be a big help to a novice....
-steve
Object relationship | (Pattern) | Implementation
---------------------------------------------------------------------------------------- 1 1 | Add prop to A: b_id A --------- B | In A call Bs (Specialist of B): my_b = Bs.getItem(b_id)
---------------------------------------------------------------------------------------- n 1 | Add prop to B: a_id A --------- B | Add method to Bs (Specialist of B): getBsForA(a_id) | In A call Bs: my_b_list = Bs.getBsForA(a_id)
---------------------------------------------------------------------------------------- n n | ? A --------- B |
---------------------------------------------------------------------------------------- n [XOR A] 1 | Add Specialist Xs implementing role of A and B A ------------- | Add prop to C: x_id n [XOR A] 1 C | In A, B call Xs: my_x = Xs.getItem(x_id) B -------------- | (Participant-Transaction)| (A and B - Participants, C - Transaction)
---------------------------------------------------------------------------------------- [XOR A] 1 n | Add prop to B, C: a_id ------------ B | In B, C call As (Specialist of A): my_a = As.getItem(a_id) A [XOR A] 1 n | ------------ C | (can't do reverse connection?)
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Does anyone think this would be useful? Can we get the experts to expand/correct/verify this? Obviously more relationship types need to be added, and also some extra information is needed (such as who's responsible to set the id attributes and how, when and how reverse connections are done, etc.).
Itai
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