Schema Reference

A data model file has three top-level sections: [meta], [enums], and [[classes]].

Meta

[meta]
id = "my_device"        # Namespace identifier (required)
version = "1.0.0"       # Semantic version (required)
doc = "Description"     # Optional documentation

The id is used to prefix all generated #define names: DM_KEY_{ID}_{CLASS}_{KEY}.

Enums

Enums define named integer-to-label mappings reusable across keys.

[enums.mode]
doc = "Operating mode"

[enums.mode.values]
off = 0
idle = 1
active = 2

# Optional: per-variant overrides
[enums.mode.variants.compact]
off = 0
active = 1

Reference an enum on a key with enum = "mode". The enum values appear as comments in the generated key_definitions.h.

Classes

Classes group related keys within a namespace. A namespace can have up to 31 classes, each with up to 1023 keys.

[[classes]]
id = "status"
doc = "Runtime status"

    [[classes.keys]]
    id = "temperature"
    type = "uint16"
    # ... attributes

Key Attributes

Attribute	Type	Default	Description
`id`	string	(required)	Key identifier
`type`	string	(required)	Data type (see below)
`default`	value	type zero	Default value
`defaults`	table	`{}`	Per-variant default overrides
`enum`	string	none	Reference to an `[enums]` entry
`max_size`	integer	none	Max bytes (required for string/binary)
`read_only`	bool	`false`	Prevent modification at runtime
`thread_safe`	bool	`false`	Protect with target mutex
`persistent`	bool	`false`	Include in binary save/load
`event`	bool	`false`	Fire callback on value change
`helpers`	bool	`false`	Generate named getter/setter functions
`unit`	string	none	Physical unit (documentary)
`doc`	string	none	Documentation string

Data Types

Type	C Type	Size	Notes
`bool`	`bool`	1 bit	Packed into uint32_t bitfields
`uint8`	`uint8_t`	1 byte
`int8`	`int8_t`	1 byte
`uint16`	`uint16_t`	2 bytes
`int16`	`int16_t`	2 bytes
`uint32`	`uint32_t`	4 bytes
`int32`	`int32_t`	4 bytes
`string`	`char[]`	max_size	Requires `max_size` attribute
`binary`	`uint8_t[]`	max_size	Requires `max_size` (schema only, codegen pending)

Per-Variant Defaults

Keys can have different default values for different product variants:

[[classes.keys]]
id = "threshold"
type = "uint8"
default = 10              # Base default

[classes.keys.defaults]
compact = 5               # Override for "compact" variant
pro = 15                  # Override for "pro" variant

The base default applies when no variant-specific override exists.

Constraints

string and binary types must specify max_size
read_only keys cannot be persistent (validated at parse time)
enum references must point to a defined [enums] entry
Class IDs must be unique within a namespace
Key IDs must be unique within a class