A minimal pipeline

This chapter walks through the core concepts of pondrs using a minimal example. The same example appears on the introduction page — here we break it apart and explain each piece in detail.

The example reads a CSV of sensor readings, computes the mean, compares it against a threshold parameter, and writes a JSON report. The following sections explain each concept:

• Parameters — read-only values loaded from YAML (Param<f64>)
• Datasets — the Dataset trait and the concrete types used here (PolarsCsvDataset, MemoryDataset, JsonDataset)
• Catalog — the struct that groups datasets together
• Nodes — the Node struct that connects a function to its input/output datasets
• Steps — how nodes are composed into a sequence that the runner can execute
• App — how App ties everything together and provides CLI dispatch