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@startuml data-model
!theme plain
title Data Model Core Abstractions
class attribute {
+ hash: SHA256
+ value: term()
}
class tuple {
+ hash: SHA256
+ relation: atom()
+ attribute_map: #{name => hash}
}
class relation {
+ hash: SHA256
+ name: atom()
+ tree: merkle_tree()
+ schema: #{attr => type_relation}
+ constraints: constraints()
+ cardinality: {finite, N} | aleph_zero | continuum
+ generator: function() | undefined
+ provenance: provenance()
}
class type_relation {
+ name: atom()
+ erlang_type: type()
+ membership_predicate: function()
+ unfold_generator: function()
+ cardinality: aleph_zero | continuum
}
class database_state {
+ hash: SHA256
+ name: atom()
+ tree: merkle_tree()
+ relations: #{name => hash}
+ type_relations: #{name => type_relation}
+ timestamp: integer()
}
database_state "1" *-- "many" relation : contains
database_state "1" *-- "many" type_relation : defines types
relation "1" *-- "many" tuple : contains
tuple "1" *-- "many" attribute : references
relation --> type_relation : schema references
note right of attribute
Content-Addressed Storage:
- SHA-256 hash of value
- Automatic deduplication
- Immutable once stored
Value Validation:
Value must be member of
type relation specified in schema
end note
note right of relation
Storage Strategy:
- Finite: Merkle tree (materialized)
- Infinite: Generator (lazy)
Type Relations:
- Primitives: natural, integer, real, string
- Composite: views over other relations
end note
note left of type_relation
**Schema Philosophy:**
Attributes are typed by type relations (not primitives).
Types are relations (stored as infinite relations).
Schema validation = membership checking.
**Type Relations are Relations:**
They define domains via:
1. Erlang type constraint
2. Additional predicates
3. Unfold generator for enumeration
Examples:
- natural[X] :- integer[X], X >= 0
- complex[X] :- X is (A,B), real[A], real[B]
end note
note bottom of database_state
**Schema Example:**
employee relation schema:
#{
name => non_empty_string, % type relation
age => natural, % type relation
salary => positive_integer % type relation
}
Each schema value is a reference to a type relation,
NOT a primitive type string like "integer"
end note
@enduml
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