System Initiative

--- outline: level: [2, 3, 4] prev: text: 'The Distributed Execution Engine' link: '/explanation/architecture/engine' next: text: 'Change Control' link: '/explanation/architecture/change-control' --- # The Data Model: Immutable Snapshots The workspace snapshot, an immutable directed acyclic graph ([DAG](https://en.wikipedia.org/wiki/Directed_acyclic_graph)), is the core data type in System Initiative and represents the complete system state at a specific point in time. ## Snapshot Structure The structure begins with a single root node and a collection of direct neighbors that each represent a different category of primitives within System Initiative. Every node in the snapshot is connected indirectly to the root through the categories. ### Nodes There are several distinct node types in the snapshot, including but not limited to: - __Modules:__ Portable collections of schemas and functions - __Schemas:__ Component type definitions with property schemas, validation rules, and function definitions - __Functions:__ Executable code units with dependency declarations and execution metadata - __Components:__ An instance of a schema, with all configuration, relationships, and resource tracking if applicable - __Values:__ Configuration data, inputs to functions, computed results, and provider responses - __Views:__ Partition containing a set of components - __Secrets:__ Reference pointer to an encrypted credential - __Actions:__ Intended operations for external system modification or interaction Nodes contain metadata, pointers to content-addressable storage (CAS) objects, and a Merkle-tree hash of all downstream nodes and edges. This design enables: - Deduplication of identical content across snapshots - Atomic updates to content through pointer swapping - Efficient node differentiation through Merkle-tree comparison ### Edges Edges encode multiple relationship types that enable deterministic graph traversals, for example: - Containment: Hierarchical ownership (Ex: Views contain components) - Dependency: Execution ordering constraints (Ex: Function A depends on the output of function B) - Lineage: Definition tracking and versioning (Ex: Component was created from Schema Variant A) ## Versioning and Copy-on-Write Semantics Versioning of snapshots is explicit through the use of [change sets](./change-control.md). During a mutation, the source snapshot establishes a baseline, and all nodes/edges are cloned using copy-on-write semantics - retaining any unchanged pointers to relevant CAS objects. This approach enables rapid snapshot creation and efficient storage utilization while maintaining immutability guarantees. The Merkle-tree hash allows fast snapshot comparison, enabling the engine to compute minimal mutation sets when synchronizing or replaying changes.