如何设计这个领域模型？

Question

So I've the following Domain:

• Applications and Versions, they are actually software applications
• Devices, the devices on which the applications are installed
• Installed Applications on Devices
• Notification Subscription by installed Applications

So far, I've end up with the following model:

• Application entity, which is defined by a name, an os and a type
• Version value object, which basically wraps version informations (major, minor, etc.)
• Release entity, which is a composed object referencing an Application entity and embedding a Version value object
• Device entity, which is identified by a serial number
• NotitificationSubscription entity (to allow me to Query by attribute)

Now I'm wondering how to "associate" Device entity, Release and the NotificationSubscription because it should be associated to an "installed" Release on a Device and include some extra information (like an authentication token).

Given the limitation of my ORM (Doctrine2) & RDMS (MySQL) I'm stuck at how to find a good design.

Imagine the following workflow:

1. I fetch the Device entity from Database identified by its Serial Number
2. I determine if the Release the Device is running from is already associated with it, if no, I create an association
3. I need then to add or remove a NotificationSubscription for the current Device Release association

My problem is I end up with much indirection.

To allow me to set extra data to the association, I created an Association Class which is itself an Entity referencing both a Device and a Release.

A device may have different Release installed and running on it, so for example, I don't know how to query the following information: "Fetches all the notification subscriptions for the current release for the current device"

I obviously added a method in a Repository findSubscriptionsByDeviceAndRelease($device, $release); which means that I can query this information by both using the repository and through the graph $device->getInstalledReleases()->filter($identifiedRelease)->getNotificationSubscriptions();

Any ideas?

Answer 1

Keep it simple: you don't need a domain model here, you just need a good entity-relationship model. You probably don't need Doctrine either, since sql queries should be simple enough.