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FeSTL Python Interface

Python bindings for the Online Signal Temporal Logic (STL) monitoring library.

Installation

You can install the FeSTL Python interface using pip:

pip install festl-python

Quick Start

import festl_python as festl

# Define an STL formula: Always[0,5](x > 0.5)
formula = festl.Formula.always(0, 5, festl.Formula.gt("x", 0.5))

# Create a monitor with Rosi semantics
monitor = festl.Monitor(formula, semantics="Rosi")

# Feed data and get verdicts
result = monitor.update("x", 1.0, 0.0)
for ts, val in result.verdicts():
    print(f"t={ts}: {val}")

# Or access structured data via dictionary
result_dict = result.to_dict()
for evaluation in result_dict['evaluations']:
    print(evaluation['outputs'])

Features

Multiple Semantics

The library supports four types of monitoring semantics:

  1. DelayedQualitative (semantics="DelayedQualitative"): Boolean satisfaction with delayed evaluation

    • Returns: True or False
    • Waits for complete information before producing verdicts

  2. EagerQualitative (semantics="EagerQualitative"): Boolean satisfaction with eager evaluation

    • Returns: True or False
    • Produces verdicts as soon as possible

  3. DelayedQuantitative (semantics="DelayedQuantitative", default): Quantitative robustness as a single value

    • Returns: Float value (positive = satisfied, negative = violated)

  4. Rosi (semantics="Rosi"): Robustness as an interval

    • Returns: Tuple (min, max) representing robustness interval

Monitoring Algorithms

  • Incremental (algorithm="Incremental", default): Efficient online monitoring using sliding windows
  • Naive (algorithm="Naive"): Simple but less efficient approach

Signal Synchronization

  • ZeroOrderHold (synchronization="ZeroOrderHold", default): Zero-order hold interpolation
  • Linear (synchronization="Linear"): Linear interpolation
  • None (synchronization="None"): No interpolation

Constructing STL Formulas

You can construct STL formulas using the provided API. For example:

# Define a formula: Always[0,5](x > 0.5)
formula = festl.Formula.always(0, 5, festl.Formula.gt("x", 0.5))
# using parser
formula = festl.parse_formula("G[0,5](x > 0.5)")

This creates a formula that states "x should always be greater than 0.5 in the interval [0, 5]". See the API reference for more details on constructing formulas.