tom_som_python_runtime — generic Python SOM runtime

> Cross-references. > tom_specs_model/doc/som_multiplatform_spec_model.md > is the SOM authority: SOM §9 decides what a runtime must contain, SOM §6 > decides the split between the generic and the typed access path, SOM §11 and > SOM §12 decide the *.md and *.docspecs.yaml formats, and SOM §19 > decides the conformance corpus this port is measured against. > tom_specs_model/doc/som_toolchains.md > decides this language plane's build and verify toolchain. This README says how > to use this package's code; those documents own the model, the formats and > the rules, and nothing here restates them.

Python port of the generic TomSpecs object-model runtime (paths, model, reflection, document, validator, YAML/Markdown codecs).

Where this fits

TomSpecs specifications are documents with a typed shape: a spec model describes which sections exist, what each may contain and how it serializes. The SOM makes that model usable from nine languages, and each language is a pair — a hand-written runtime (this package) holding everything that is the same everywhere, and a generated tom_som_python_v0 facade holding the typed classes for one model version. Without the split, every regeneration would rewrite the document store, the codecs and the validator; with it, the generator emits only what actually changes when the model changes.

This package is a faithful transcription of the Dart reference, tom_som_dart_runtime — it invents nothing, and "faithful" is a measured claim rather than an intention: every port is validated against the same goldens, byte for byte (SOM §19). Reach for it directly when you drive the generic API by section path; otherwise install the typed facade, which pulls this in.

Overview

A SOM document is sparse and path-keyed: values live in three stores (content, form fields, list sequences) under the globally-unique section-ID path they belong to, and an absent key means "no value" rather than an empty one. SpecDocument is that store. Everything else in the package is a layer over it — the meta-model (SpecModel, SpecReflection) that makes generic navigation possible without generated classes, the byte-stable YAML and Markdown codecs, the editing and validation tiers, and the Phase-4 CodeSpecs extractor.

It holds no document values of its own and contains no generated typed classes — those belong to the per-language tom_som_<lang>_v0 packages.

Installation

pip install tom_som_python_runtime

The distribution is tom_som_python_runtime; the importable package is tom_som_runtime. The version tracks the TomSpecs model version, and tom_som_python_v0 pins the same one — upgrade both together (SOM §4.2). See readme_howtointegrate.md for the PyPI / git / editable routes and how to pin.

Features

Modules

Module	Responsibility
`spec_paths`	The section-path grammar (root / child / list-item segments).
`spec_model`	The meta-data loader — the exported class graph (`SpecModel`).
`spec_reflection`	Value-free enumeration + path resolution (`SpecReflection`).
`spec_document`	A sparse in-memory document — values keyed by section path.
`spec_typed_values`	Parse/format at the store boundary — the one place the text form of an `int` / `double` / `num` / `bool` / enum-name is decided.
`spec_editor`	The generic meta-model-driven modification API ( `SpecEditor` , YRD7) — typed edits over any path, without a generated facade.
`spec_validator`	Validates a document's values against the model.
`spec_text_pattern`	The portable pattern subset ( `SomTextPattern` ) — a hand-written leftmost-first backtracker over UTF-16 code units, so match spans agree with every other runtime. `re` is not used, and this module converts to code units explicitly ( `utf16_units` ) rather than iterating characters: a Python string is a sequence of code points , which agrees with code units throughout the BMP and diverges above it.
`spec_query`	The lexical/structural query surface ( `SpecQueryEngine` , `SpecQuery` , `SpecQueryCursor` ) plus the flat tier-1 node projection ( `SpecNodeProjection` ).
`spec_node_creation`	The constrained node-creation gate ( `check_add_node` , `SpecNodeCreator` ) — a document may only grow in ways the model permits.
`spec_document_yaml`	Byte-stable `*.docspecs.yaml` codec (`SOM §12`).
`spec_document_markdown`	Meta-data-driven Markdown import/export codec (`SOM §11`).
`spec_codespecs_extract`	The Phase-4 CodeSpecs specification extract generator ( `CodeSpecsExtractor` , `CodeSpecsAreaCatalog` ) — one extract per CodeSpecs area, collecting every value `@CodeSpecKind` routes there verbatim and with provenance . It copies and indexes; it never summarises or composes. Walks one `@Document` root, resolved at construction from an optional root-type argument ( `codespecs_prompt.md` §5).

Quick start

from tom_som_runtime import SpecDocument

doc = SpecDocument()
doc.set_content("SBP/content", "A platform that unifies our order systems.")
print(doc.content("SBP/content"))
# A platform that unifies our order systems.

Usage

The generic path

Load the exported class graph, then resolve paths against it — no generated classes involved:

import json
from tom_som_runtime import SpecModel, SpecReflection, validate_document

model = SpecModel.from_json(json.loads(meta_json))
reflection = SpecReflection(model)

print(reflection.resolve("SBP/content") is not None)
# True
print(validate_document(model, doc) == [])
# True

Requirements

Python ≥ 3.9
PyYAML ≥ 6.0 (the YAML decoder + the encoder's self-verification, mirroring

Dart's package:yaml).

This is the one SOM runtime with an external dependency; the other eight ship hand-rolled, dependency-free readers.

Building and running the tests

Correctness is defined by the shared, language-agnostic conformance corpus in tom_som_conformance/corpus, generated from the Dart reference. This port is validated against the exact same goldens every other port uses (SOM §19):

python3 tests/conformance_runner.py   # → "OK: N checks passed"
./run_tests.sh                        # conformance + the per-module suites

The runner asserts byte-for-byte equality of the YAML and Markdown encodings, the document round-trips, and the reflection / validation / operations behaviour.

Architecture

        typed path                          generic path
  tom_som_python_v0 facade  ─────▶   SomNode / SomScalar / SomList
            │                                   │
            └───────────────┬───────────────────┘
                            ▼
                      SpecDocument         sparse, path-keyed value stores
                            │
        ┌───────────────────┼────────────────────┐
        ▼                   ▼                    ▼
  SpecReflection       SpecEditor          spec_document_yaml
  SpecQueryEngine      validate_document   spec_document_markdown
        │
        ▼
     SpecModel  ◀── meta/spec_model.meta.json

Type	Responsibility
`SpecDocument`	The sparse, path-keyed store of a document's content, form and list values.
`SpecModel`	The exported class graph — roots, classes, fields, annotations.
`SpecReflection`	Resolves and enumerates paths against the model without reading values.
`SpecEditor`	Typed edits over any path, driven by the meta-model rather than by generated classes.
`SpecNodeCreator`	The creation gate — a document may only grow in ways the model permits.
`validate_document`	The instance tier: a filled document's values checked against the model.
`spec_document_yaml`	Byte-stable `*.docspecs.yaml` encode/decode.
`spec_document_markdown`	DocSpecs-conform Markdown export, parse and round-trip.
`SpecQueryEngine`	Lexical/structural search over a document, matching with `SomTextPattern`.
`CodeSpecsExtractor`	The Phase-4 extract generator — one verbatim, cited extract per CodeSpecs area.
`SomNode` / `SomScalar` / `SomList`	The editing-facade base types the generated `tom_som_python_v0` classes extend.

Ecosystem

  tom_specs_model ──▶ tom_specs_clitool ──generate_som──▶ tom_som_python_v0
   (the model)          (the generator)                     (typed facade)
                                                                  │ depends on
                                                                  ▼
                                                      tom_som_python_runtime  ← this package
                                                                  │ validated against
                                                                  ▼
                                                         tom_som_conformance
                                                          (shared corpus)

Further documentation

TomSpecs subject matter — the authorities this package implements:

Document	Authority for
index.md	The catalogue of every TomSpecs subject-matter document, and the `§` citation convention.
som_multiplatform_spec_model.md	What a SOM runtime must contain, the two access paths, the `.md` and `.docspecs.yaml` formats, the validator, and the conformance corpus.
som_toolchains.md	This language plane's build and verify toolchain, and the reference host.
tom_specs_model_meta_schema.md	The on-disk schema of `meta/spec_model.meta.json`, which `SpecModel` loads.

This package — its own guides:

Guide	Covers
readme_howtointegrate.md	Every dependency route and how to pin the version.

Siblings — packages you will reach for next:

Package	What it is
tom_som_python_v0	The generated typed facade over this runtime — the normal path.
tom_som_dart_runtime	The Dart reference this port transcribes.
tom_som_conformance	The shared corpus and the cross-language drivers that run every port against it.

Status

Version 1.1.0, tracking the TomSpecs model version. Covered by 10 test files; the conformance runner reports OK: 874 checks passed and ./run_tests.sh is green.