MeTTa Kernel

Appearance

metta.tables ​

Source: extensions/python/metta/tables.py.

Derive a whole table-backed space provider from MeTTa bridge declarations, so the contract is rewrite rules and both directions of the boundary fall out of matching them. The module is metta.tables because a subscription bridge is already the standing bridge RULE between two spaces (metta.subscribe.bridge); the two are the same idea at two boundaries, a declared correspondence the engine keeps live.

(bridge (edge $a $b) (row edges (a $a) (b $b)))

One pattern pair relates an atom shape to a table shape. Matched left-to-right a query becomes WHERE and an add becomes INSERT; matched right-to-left a row becomes the atom. A provider takes a SCHEMA, any number of declarations: a schema is a set of rewrite rules the way a function is a set of equations, so a query answers the union of every shape it admits, exactly as overlapping equations answer together. The one place the equation reading is deliberately NOT copied is add: a ground atom two shapes admit is refused naming both, because storing it twice would invent an occurrence, and a multiset must not.

This is the bidirectional-transformations literature's third approach, writing the consistency relation and deriving both transformations , and the lens round-trip laws are what check_space_provider verifies against the derived claims.

Declarations may live in &metta, ctx-scoped like every other contract atom: declare(m, "&crm", "(bridge (edge $a $b) (row edges ...))") writes (bridge &crm (edge $a $b) (row edges ...)) there, MeTTa source can add the same atom itself, and TableBridge.from_context(m, "&crm", connection) reads every one back, so a program carries its schema as knowledge and the attach is one line.

The entries below reproduce the source signatures and docstrings.

add ​

python
def add(space: Any, head: Any, data: Any) -> int:

Add a tabular source to a space as (head column...) facts.

Executes ​

python
class Executes(Protocol):

The slice of a DB-API connection the bridge stands on.

Executes.execute ​

python
def execute(self, sql: str, parameters: Any = ..., /) -> Any:

No docstring is defined.

Executes.commit ​

python
def commit(self) -> None:

No docstring is defined.

Executes.rollback ​

python
def rollback(self) -> None:

No docstring is defined.

TableBridge ​

python
class TableBridge(SpaceProvider):

Every provider operation derived from the declarations; nothing in here is specific to any table.

TableBridge.from_context ​

python
def from_context(cls, m: Any, name: str, connection: Executes) -> TableBridge:

The provider for every (bridge <name> <shape> <row>) atom in &metta, so a schema declared from MeTTa source, or by declare() below, becomes a provider in one line.

TableBridge.atoms ​

python
def atoms(self) -> Iterator[Atom]:

No docstring is defined.

TableBridge.match ​

python
def match(self, pattern: Atom, *, limit: int | None = None) -> Iterator[Atom]:

No docstring is defined.

TableBridge.pushdown ​

python
def pushdown(self, pattern: Atom) -> str:

No docstring is defined.

TableBridge.add ​

python
def add(self, atom: Atom) -> None:

No docstring is defined.

TableBridge.remove ​

python
def remove(self, pattern: Atom) -> bool:

No docstring is defined.

TableBridge.clear ​

python
def clear(self) -> None:

No docstring is defined.

TableBridge.begin ​

python
def begin(self) -> None:

No docstring is defined.

TableBridge.commit ​

python
def commit(self) -> None:

No docstring is defined.

TableBridge.rollback ​

python
def rollback(self) -> None:

No docstring is defined.

declare ​

python
def declare(m: Any, name: str, declaration: Atom | str) -> Atom:

Write one ctx-scoped bridge declaration into &metta, where explain and any program can read the schema, and from_context will.

Released under the MIT License.

MesTTo