schema overview

Domain model

Almost every system design starts with defining domain models, what do they consist of and how they relate to each other. This is the language PMs and customers understand and it allows to set up universal dictionary for interfaces and implementations. So lets start with a few abstract entities:

Every entity can be described by multiple representations: ID, URI, record or even binary data like images. We can capture this concept by introducing multi-types, collections of types that can act as different representations of the same entity.

User is a multi-type that can be either UserId or UserRecord, File can be either FileId or FileRecord and so on.

Now we have records, fields and field types. FileRecord.name is probably a string, but what’s the type of FileRecord.owner? Before deciding on it lets step back and think about the nature of a field. Fields define relationships between entities and field names hint at their semantics. We don’t care about implementation details at this point, all we want to say is that a File has an owner which is a User