Custom literals and types

TripleModel maps common scalars to XSD literals automatically. For Decimal, UUID, and Enum, built-in converters are registered. You can add your own types with the literal registry.

Built-in support

Python type	Notes
`Decimal`	XSD decimal literal
`UUID`	Stored as string, parsed back to `UUID`
`Enum`	Uses `enum.value` as string

from decimal import Decimal
from enum import Enum
from triplemodel import TripleModel, rdf_field

class Status(Enum):
    ACTIVE = "active"
    INACTIVE = "inactive"

class Item(TripleModel):
    class Rdf:
        namespace = "http://example.org/items/"
        type_uri = "http://example.org/Item"
        id_field = "sku"

    sku: str
    price: Decimal = rdf_field("http://example.org/price")
    status: Status = rdf_field("http://example.org/status")

item = Item(sku="1", price=Decimal("9.99"), status=Status.ACTIVE)
restored = Item.from_graph(item.to_graph(), item.subject_uri())

Register a custom type

from pyoxigraph import Literal, NamedNode
from triplemodel import XSD, register_literal_type

class Money:
    def __init__(self, amount: str):
        self.amount = amount

register_literal_type(
    Money,
    to_literal=lambda m: Literal(m.amount, NamedNode(str(XSD.decimal))),
    from_literal=lambda lit: Money(str(lit)),
    datatype=str(XSD.decimal),
)

Use NamedNode for the XSD datatype IRI (import from pyoxigraph). Custom converters should return pyoxigraph Literal values on export.

Registry lookup runs before generic XSD coercion in python_to_term / term_to_python.

Enums

Subclass enum.Enum (or StrEnum on Python 3.11+). Import coerces the literal string to the enum member; export writes member.value.

Next: Working with graphs →