civic-digital-twins 0.6.0

Civic-Digital-Twins Modeling Framework

Civic-Digital-Twins Modeling Framework

This repository contains a Python package implementing a Civic-Digital-Twins modeling framework. The framework is designed to support defining digital twins models and evaluating them in simulated environments with varying contextual conditions. We develop this package at @fbk-most, a research unit at Fondazione Bruno Kessler.

Note: this package is currently in an early development stage.

Conceptual Overview

The framework is organised in three layers.

Engine layer

The engine (civic_digital_twins.dt_model.engine) is an embedded DSL compiler. The programmer builds a computation graph (DAG) by composing typed nodes — constants, placeholders, and operations — using ordinary Python expressions. The graph is then linearised by topological sorting and evaluated by a NumPy-based interpreter that maps each node to the corresponding numpy operation.

from civic_digital_twins.dt_model.engine.frontend import graph, linearize
from civic_digital_twins.dt_model.engine.numpybackend import executor
import numpy as np

a = graph.placeholder("a")
b = graph.placeholder("b")
c = a * 2 + b

state = executor.State(values={a: np.asarray(3.0), b: np.asarray(1.0)})
executor.evaluate_nodes(state, *linearize.forest(c))
print(state.get_node_value(c))  # 7.0

See docs/design/dd-cdt-engine.md for a full description of the engine.

Model / simulation layer

The model layer (civic_digital_twins.dt_model) provides higher-level abstractions built on top of the engine:

• Index / TimeseriesIndex — named wrappers around graph nodes. An index can be a constant, a distribution (sampled at evaluation time), or a formula.
• Model — a named collection of Index objects. A model is abstract when some indexes are unbound (distributions or placeholders); it becomes concrete once all indexes are resolved.
• Evaluation — evaluates a model over a sequence of weighted scenarios, each of which maps every abstract index to a concrete value.
• Ensemble / WeightedScenario — a protocol and type alias that define the scenario contract consumed by Evaluation.

from civic_digital_twins.dt_model import Evaluation, Model
from civic_digital_twins.dt_model.model.index import Index, UniformDistIndex

# Two distribution-backed indexes
x = UniformDistIndex("x", loc=0.0, scale=1.0)
y = UniformDistIndex("y", loc=0.0, scale=1.0)
result = Index("result", x + y)

model = Model("example", [x, y, result])

Usage patterns

Two concrete usage patterns are illustrated in the examples/ directory.

Direct pattern (examples/mobility_bologna/) — the model consists entirely of Index and TimeseriesIndex objects; DistributionEnsemble samples each distribution-backed index to produce weighted scenarios; Evaluation.evaluate() runs the engine and returns an EvaluationResult.

Vertical extension pattern (examples/overtourism_molveno/) — the domain-specific layer introduces ContextVariable, PresenceVariable, Constraint, and OvertourismModel on top of the core types. OvertourismEnsemble samples context variables and produces weighted scenarios. Evaluation.evaluate(axes={pv: array, …}) evaluates the model on a multi-dimensional grid, returning arrays of shape (N₀, …, Nₖ, S) where S is the number of scenarios and each Nᵢ corresponds to one presence axis.

Installation

The package name is civic-digital-twins on PyPi. Install using pip:

pip install civic-digital-twins

or, using uv:

uv add civic-digital-twins

The main package name is civic_digital_twins:

import civic_digital_twins

or

from civic_digital_twins import dt_model

Minimum Python Version

Python 3.11.

API Stability Guarantees

The package is currently in an early development stage. We do not anticipate breaking APIs without a good reason to do so, yet, breaking changes may occur from time to time. We generally expect subpackages within the top-level package to change more frequently.

Development Setup

We use uv for managing the development environment.

To get started, run:

git clone https://github.com/fbk-most/civic-digital-twins
cd civic-digital-twins
uv venv
source .venv/bin/activate
uv sync --dev

We use pytest for testing. To run tests use this command (from inside the virtual environment):

pytest

Each pull request is automatically tested using GitHub Actions. The workflow is defined in .github/workflows/test.yml.

Updating Dependencies

uv self update
uv sync --upgrade

Releasing

1. Make sure the version number in pyproject.toml is correct.

2. Update CHANGELOG.md: set the release date on the current version section and add a comparison link at the bottom.

3. Create and push a git tag: git tag v<version> && git push origin v<version>.

4. Build the package: uv build.

5. Check the artifacts: uv run --with twine twine check dist/*.

6. Upload to PyPI: uv run --with twine twine upload dist/*.

Documentation

Document	Description
Getting Started	Step-by-step guide covering the direct and vertical extension usage patterns.
dd-cdt-engine.md	DSL compiler engine — graph nodes, topological sorting, NumPy executor.
dd-cdt-model.md	Model / simulation layer — Model, Evaluation, WeightedScenario, and the vertical extension pattern.

License

SPDX-License-Identifier: Apache-2.0