gds-framework 0.3.0

Generalized Dynamical Systems — typed compositional specifications for complex systems

gds-framework

Typed compositional specifications for complex systems, grounded in Generalized Dynamical Systems theory (Zargham & Shorish, 2022).

Table of Contents

• Quick Start
• What is this?
• Architecture
• Examples
• What's Included
• Glossary
• Intellectual Lineage
• Status
• Credits & Attribution

Quick Start

pip install gds-framework

from gds import (
    BoundaryAction, Policy, ControlAction,
    interface, Wiring,
    compile_system, verify,
)
from gds.ir.models import FlowDirection

# Define blocks with GDS roles and typed interfaces
sensor = BoundaryAction(
    name="Temperature Sensor",
    interface=interface(forward_out=["Temperature"]),
)
controller = Policy(
    name="PID Controller",
    interface=interface(
        forward_in=["Temperature", "Setpoint"],
        forward_out=["Heater Command"],
        backward_in=["Energy Cost"],
    ),
)
plant = ControlAction(
    name="Room",
    interface=interface(
        forward_in=["Heater Command"],
        forward_out=["Temperature"],
        backward_out=["Energy Cost"],
    ),
)

# Compose with operators — types checked at construction time
system = (sensor >> controller >> plant).feedback([
    Wiring(
        source_block="Room", source_port="Energy Cost",
        target_block="PID Controller", target_port="Energy Cost",
        direction=FlowDirection.CONTRAVARIANT,
    )
])

# Compile to flat IR and verify
ir = compile_system("Thermostat", system)
report = verify(ir)
print(f"{len(ir.blocks)} blocks, {len(ir.wirings)} wirings")
# 3 blocks, 3 wirings
print(f"{report.checks_passed}/{report.checks_total} checks passed")
# 13/14 checks passed (G-002 flags BoundaryAction for having no inputs — expected)

What is this?

gds-framework is a foundation layer for specifying dynamical systems as compositions of typed blocks. It provides the domain-neutral primitives — you bring the domain knowledge.

gds-framework                          Your domain package
─────────────────                       ──────────────────
Block, Interface, Port                  PredatorBlock, PreyBlock
>> | .feedback() .loop()                predator >> prey >> environment
TypeDef, Space, Entity                  Population(int, ≥0), EcosystemState
GDSSpec, verify()                       check_conservation(), check_stability()
compile_system() → SystemIR             visualize(), simulate()

A Generalized Dynamical System is a pair {h, X} where X is a state space (any data structure) and h: X → X is a state transition map. The GDS canonical form decomposes h into a pipeline of typed blocks — observations, decisions, and state updates — that compose via wiring:

GDS concept	Paper notation	gds-framework
State Space	X	Entity with StateVariables
Exogenous observation	g(·)	BoundaryAction
Decision / policy	g: X → U_x	Policy
State update	f: X × U_x → X	Mechanism
Admissible input constraint	U: X → ℘(U)	ControlAction
Transition map	h = f|_x ∘ g	Composed wiring (>>)
Trajectory	x₀, x₁, ...	Temporal loop (.loop())

This decomposition is the same regardless of whether you're modeling a biological ecosystem, a control system, a financial market, or a game-theoretic interaction. gds-framework provides the decomposition machinery; domain packages provide the semantics.

Architecture: foundation + domain packages

gds-framework (pip install gds-framework)
│
│  Domain-neutral composition algebra, typed spaces,
│  state model, verification engine, flat IR compiler.
│  No domain-specific concepts. No simulation. No rendering.
│
├── Domain: Ecology
│   └── Predator-prey dynamics, population models, SIR epidemiology
│
├── Domain: Control Systems
│   └── Controllers, plants, sensors, stability/controllability checks
│
├── Domain: Financial Systems
│   └── Insurance contracts, market mechanisms, conservation of flows
│
├── Domain: Game Theory
│   └── Iterated games, strategy adaptation, equilibrium analysis
│
└── Domain: Multi-Agent Systems
    └── Agent policies, environment dynamics, coordination protocols

Each domain package is a thin layer. The heavy lifting — composition, compilation, verification, querying — lives in gds-framework.

Example: what lives where

Consider modeling a Lotka-Volterra predator-prey system as a GDS. The state space is (prey_population, predator_population). Each evaluation: the environment is observed, growth/predation rates are computed, populations are updated.

gds-framework provides (domain-neutral):

• TypeDef(name="Population", python_type=int, constraint=lambda x: x >= 0) — constrained types
• Entity(name="Prey", variables={"population": ...}) — state containers
• BoundaryAction, Policy, Mechanism — block roles with interface constraints
• >> composition with type checking, .loop() for temporal iteration
• verify() — are all state variables updated? any write conflicts? all blocks reachable?

A domain package would add (ecology-specific):

• Concrete block implementations with actual dynamics (Lotka-Volterra equations)
• Domain-specific verification (population conservation, extinction checks)
• Simulation execution (running trajectories from initial conditions)
• Visualization (phase plots, time series)

The same split applies to any domain. An iterated prisoner's dilemma model would use BoundaryAction for observing the opponent's last move, Policy for strategy selection (tit-for-tat, always-defect, etc.), Mechanism for payoff calculation and score update, and .loop() for repeated rounds — all composed from the same primitives.

A thermostat control system would use BoundaryAction for the temperature sensor, Policy for the PID controller, Mechanism for the room's thermal dynamics, and .feedback() for the energy cost signal flowing backward.

Examples

Five tutorial examples in gds-examples demonstrate every framework feature. Each model.py reads like a tutorial chapter with inline GDS theory commentary.

#	Example	What It Teaches	Composition
1	SIR Epidemic	Fundamentals — TypeDef, Entity, Space, 3 block roles	>> |
2	Thermostat PID	.feedback(), CONTRAVARIANT, backward ports	>> .feedback()
3	Lotka-Volterra	.loop(), COVARIANT temporal iteration	>> | .loop()
4	Prisoner's Dilemma	Nested |, multi-entity state, complex trees	| >> .loop()
5	Insurance Contract	ControlAction role, complete 4-role taxonomy	>>

Start with SIR Epidemic and work down — each introduces one new concept.

Each model generates 6 views automatically via gds-viz. Here are sample views for the SIR Epidemic:

Structural view — compiled block graph with role-based shapes and typed wiring labels

%%{init:{"theme":"neutral"}}%%
flowchart TD
    classDef boundary fill:#93c5fd,stroke:#2563eb,stroke-width:2px,color:#1e3a5f
    classDef policy fill:#fcd34d,stroke:#d97706,stroke-width:2px,color:#78350f
    classDef mechanism fill:#86efac,stroke:#16a34a,stroke-width:2px,color:#14532d
    classDef control fill:#d8b4fe,stroke:#9333ea,stroke-width:2px,color:#3b0764
    classDef generic fill:#cbd5e1,stroke:#64748b,stroke-width:1px,color:#1e293b
    Contact_Process([Contact Process]):::boundary
    Infection_Policy[Infection Policy]:::generic
    Update_Susceptible[[Update Susceptible]]:::mechanism
    Update_Infected[[Update Infected]]:::mechanism
    Update_Recovered[[Update Recovered]]:::mechanism
    Contact_Process --Contact Signal--> Infection_Policy
    Infection_Policy --Susceptible Delta--> Update_Susceptible
    Infection_Policy --Infected Delta--> Update_Infected
    Infection_Policy --Recovered Delta--> Update_Recovered

Canonical GDS view — mathematical decomposition: X_t → U → g → f → X_{t+1}

%%{init:{"theme":"neutral"}}%%
flowchart LR
    classDef boundary fill:#93c5fd,stroke:#2563eb,stroke-width:2px,color:#1e3a5f
    classDef policy fill:#fcd34d,stroke:#d97706,stroke-width:2px,color:#78350f
    classDef mechanism fill:#86efac,stroke:#16a34a,stroke-width:2px,color:#14532d
    classDef control fill:#d8b4fe,stroke:#9333ea,stroke-width:2px,color:#3b0764
    classDef generic fill:#cbd5e1,stroke:#64748b,stroke-width:1px,color:#1e293b
    classDef entity fill:#e2e8f0,stroke:#475569,stroke-width:2px,color:#0f172a
    classDef param fill:#fdba74,stroke:#ea580c,stroke-width:2px,color:#7c2d12
    classDef state fill:#5eead4,stroke:#0d9488,stroke-width:2px,color:#134e4a
    classDef target fill:#fca5a5,stroke:#dc2626,stroke-width:2px,color:#7f1d1d
    classDef empty fill:#e2e8f0,stroke:#94a3b8,stroke-width:1px,color:#475569
    X_t(["X_t<br/>Susceptible.count, Infected.count, Recovered.count"]):::state
    X_next(["X_{t+1}<br/>Susceptible.count, Infected.count, Recovered.count"]):::state
    Theta{{"Θ<br/>contact_rate, beta, gamma"}}:::param
    subgraph U ["Boundary (U)"]
        Contact_Process[Contact Process]:::boundary
    end
    subgraph g ["Policy (g)"]
        Infection_Policy[Infection Policy]:::policy
    end
    subgraph f ["Mechanism (f)"]
        Update_Susceptible[Update Susceptible]:::mechanism
        Update_Infected[Update Infected]:::mechanism
        Update_Recovered[Update Recovered]:::mechanism
    end
    X_t --> U
    U --> g
    g --> f
    Update_Susceptible -.-> |Susceptible.count| X_next
    Update_Infected -.-> |Infected.count| X_next
    Update_Recovered -.-> |Recovered.count| X_next
    Theta -.-> g
    Theta -.-> f
    style U fill:#dbeafe,stroke:#60a5fa,stroke-width:1px,color:#1e40af
    style g fill:#fef3c7,stroke:#fbbf24,stroke-width:1px,color:#92400e
    style f fill:#dcfce7,stroke:#4ade80,stroke-width:1px,color:#166534

Architecture by role — blocks grouped by GDS role with entity state cylinders

%%{init:{"theme":"neutral"}}%%
flowchart TD
    classDef boundary fill:#93c5fd,stroke:#2563eb,stroke-width:2px,color:#1e3a5f
    classDef policy fill:#fcd34d,stroke:#d97706,stroke-width:2px,color:#78350f
    classDef mechanism fill:#86efac,stroke:#16a34a,stroke-width:2px,color:#14532d
    classDef control fill:#d8b4fe,stroke:#9333ea,stroke-width:2px,color:#3b0764
    classDef generic fill:#cbd5e1,stroke:#64748b,stroke-width:1px,color:#1e293b
    classDef entity fill:#e2e8f0,stroke:#475569,stroke-width:2px,color:#0f172a
    classDef param fill:#fdba74,stroke:#ea580c,stroke-width:2px,color:#7c2d12
    classDef state fill:#5eead4,stroke:#0d9488,stroke-width:2px,color:#134e4a
    classDef target fill:#fca5a5,stroke:#dc2626,stroke-width:2px,color:#7f1d1d
    classDef empty fill:#e2e8f0,stroke:#94a3b8,stroke-width:1px,color:#475569
    subgraph boundary ["Boundary (U)"]
        Contact_Process([Contact Process]):::boundary
    end
    subgraph policy ["Policy (g)"]
        Infection_Policy[Infection Policy]:::policy
    end
    subgraph mechanism ["Mechanism (f)"]
        Update_Susceptible[[Update Susceptible]]:::mechanism
        Update_Infected[[Update Infected]]:::mechanism
        Update_Recovered[[Update Recovered]]:::mechanism
    end
    entity_Susceptible[("Susceptible<br/>count: S")]:::entity
    entity_Infected[("Infected<br/>count: I")]:::entity
    entity_Recovered[("Recovered<br/>count: R")]:::entity
    Update_Susceptible -.-> entity_Susceptible
    Update_Infected -.-> entity_Infected
    Update_Recovered -.-> entity_Recovered
    Contact_Process --ContactSignalSpace--> Infection_Policy
    Infection_Policy --DeltaSpace--> Update_Infected
    Infection_Policy --DeltaSpace--> Update_Recovered
    Infection_Policy --DeltaSpace--> Update_Susceptible
    style boundary fill:#dbeafe,stroke:#60a5fa,stroke-width:1px,color:#1e40af
    style policy fill:#fef3c7,stroke:#fbbf24,stroke-width:1px,color:#92400e
    style mechanism fill:#dcfce7,stroke:#4ade80,stroke-width:1px,color:#166534

Parameter influence — Θ → blocks → entities causal map (Thermostat PID example)

%%{init:{"theme":"neutral"}}%%
flowchart LR
    classDef boundary fill:#93c5fd,stroke:#2563eb,stroke-width:2px,color:#1e3a5f
    classDef policy fill:#fcd34d,stroke:#d97706,stroke-width:2px,color:#78350f
    classDef mechanism fill:#86efac,stroke:#16a34a,stroke-width:2px,color:#14532d
    classDef control fill:#d8b4fe,stroke:#9333ea,stroke-width:2px,color:#3b0764
    classDef generic fill:#cbd5e1,stroke:#64748b,stroke-width:1px,color:#1e293b
    classDef entity fill:#e2e8f0,stroke:#475569,stroke-width:2px,color:#0f172a
    classDef param fill:#fdba74,stroke:#ea580c,stroke-width:2px,color:#7c2d12
    classDef state fill:#5eead4,stroke:#0d9488,stroke-width:2px,color:#134e4a
    classDef target fill:#fca5a5,stroke:#dc2626,stroke-width:2px,color:#7f1d1d
    classDef empty fill:#e2e8f0,stroke:#94a3b8,stroke-width:1px,color:#475569
    param_Kd{{"Kd"}}:::param
    param_Ki{{"Ki"}}:::param
    param_Kp{{"Kp"}}:::param
    param_setpoint{{"setpoint"}}:::param
    PID_Controller[PID Controller]
    entity_Room[("Room<br/>T, E")]:::entity
    param_Kd -.-> PID_Controller
    param_Ki -.-> PID_Controller
    param_Kp -.-> PID_Controller
    param_setpoint -.-> PID_Controller
    Update_Room -.-> entity_Room
    PID_Controller --> Room_Plant
    Room_Plant --> PID_Controller
    Room_Plant --> Update_Room

The remaining 2 views (architecture by domain, traceability) are in each example's VIEWS.md. See gds-examples for the full guide.

What's Included

Layer 1 — Composition Algebra: Blocks with bidirectional typed interfaces, composed via four operators (>>, |, .feedback(), .loop()). A 3-stage compiler flattens composition trees into flat IR. Six generic verification checks validate structural properties.

Layer 2 — Specification Layer: TypeDef with runtime constraints, typed Spaces, Entity with StateVariables, block roles (BoundaryAction, Policy, Mechanism, ControlAction), GDSSpec registry, ParameterSchema for configuration space Θ, CanonicalGDS projection deriving the formal h = f ∘ g decomposition, Tagged mixin for inert semantic annotations, semantic verification (completeness, determinism, reachability, type safety, parameter references, canonical wellformedness), SpecQuery for dependency analysis, and JSON serialization.

Glossary

GDS terminology mapped to framework concepts

Term	Definition	In the framework
State (x)	The current configuration of the system — a point in the state space	A value held by StateVariables inside an Entity
State Space (X)	All possible configurations; can be any data structure, not just ℝⁿ	Product of all Entity variables, each typed by TypeDef
Exogenous Signal (z)	An external signal entering the system from outside	BoundaryAction outputs flowing through Ports. Paper uses u for the selected action; codebase uses z for exogenous signals to avoid conflation.
Decision (d)	The output of the policy mapping d = g(x, z)	Policy forward_out ports. Corresponds to the paper's selected action u ∈ U_x.
Admissible Input Space (U_x)	The set of inputs available given the current state x (paper Def 2.5)	Structural skeleton via AdmissibleInputConstraint; behavioral constraint requires runtime
Input Map (g)	Maps state and exogenous signals to a decision: g(x, z) → d	Policy blocks (endogenous decision logic)
State Update Map (f)	Takes current state and decision, produces the next state: f(x, d) → x⁺	Mechanism blocks — the only blocks that write to state
State Transition Map (h)	The composed pipeline h = f|_x ∘ g — one full step of the system	The wiring produced by >> composition
Trajectory (x₀, x₁, ...)	A sequence of states produced by repeatedly applying h	Temporal iteration via .loop()
Reachability	Can the system reach state y from state x through some sequence of inputs?	check_reachability() in the verification engine
Controllability	Can the system be steered to a target state from any nearby initial condition?	Formal property checked at the spec level
Configuration Space	The subset of X where every point is reachable from some initial condition	Characterized by transitive closure over the wiring graph

Intellectual Lineage

• GDS formalism (Roxin 1960s; Zargham & Shorish 2022) — state transitions composed over arbitrary data structures, with formal notions of reachability, controllability, and admissibility
• MSML (BlockScience) — block roles, parameter tracking, typed transmission channels
• BDP-lib (Block Diagram Protocol) — abstract/concrete separation, structural validation
• Categorical cybernetics (Ghani, Hedges et al.) — bidirectional composition with contravariant feedback

See docs/gds_deepdive.md for the full analysis.

Status

v0.2.0 — Alpha. Both layers are implemented and tested (347 tests, 99% coverage). v0.2 adds parameter typing (Θ), canonical projection (h = f ∘ g derivation), tagged metadata, and 6 Mermaid visualization views via gds-viz. The composition algebra and specification layer are stable. Domain packages and simulation execution are not yet built — gds-framework is the foundation they will build on.

License

Apache-2.0

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Built with Claude Code. All code is test-driven and human-reviewed.

Credits & Attribution

Author: Rohan Mehta — BlockScience

Theoretical foundation: Dr. Michael Zargham and Dr. Jamsheed Shorish — Generalized Dynamical Systems, Part I: Foundations (2021).

Architectural inspiration: Sean McOwen — MSML and bdp-lib.

Contributors:

• Michael Zargham — Project direction, GDS theory guidance, and technical review (BlockScience).
• Peter Hacker — Code auditing and review (BlockScience).

Lineage: Part of the cadCAD ecosystem for Complex Adaptive Dynamics.