Step and Cycle Semantics

Step and cycle fields are more than column names. Different cycler exports may use the same words for different concepts, or reuse step numbers inside each cycle.

BDS Fields

Canonical field	Export label	Meaning
cycle_index	Cycle Count	Source cycle identifier or count when available.
step_index	Step Index	Source step identifier/count from the procedure when available.
record_index	Record Index	Source record/data-point index, or generated row order.
step_time_s	Step Time (s)	Elapsed time within the active step.
test_time_s	Test Time (s)	Elapsed time from the start of the full test.

The legacy target=bdf export uses slash-unit column names and maps record_index to Step Index / 1 for older compatibility. Prefer the default bds target for new public handoff unless an integration explicitly requires the legacy BDF-style shape.

Ambiguity

BDS preserves source step and cycle values when they are present. When a source file does not contain whole-test time, BDS may reconstruct test_time_s from step time under the selected repair policy and reports that operation in warnings/provenance.

Use bds explain or conversion reports to check whether step/cycle fields came from source columns, were joined from context sheets, or were absent. Use bds.summarize_steps(df) and bds.summarize_cycles(df) for quick sanity checks after reading a file.

Audit Checks

Audit reports flag decreasing or negative cycle/step values. These warnings do not prove the file is wrong; they point to cases that need procedure-aware review before downstream aggregation.