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Documentation Index

Fetch the complete documentation index at: https://docs.siftstack.com/llms.txt

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Families in Sift are named groups of related Runs used for comparison, analysis, and historical baselines. For example, group all known-good acceptance test Runs for an engine configuration into a Family, then evaluate each new Run against the Family’s chamber pressure mean and standard deviation to flag deviations from the baseline. Once a Family is defined, you can overlay members on a shared time axis, compute aggregate statistics, and build Rules that flag when a new Run deviates from the baseline. See When to use Families for more example workflows.

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Key concepts

Families are built from four core elements:

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When to use Families

Use Families when historical data defines standard behavior and you want to compare new Runs against that baseline.

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Alignments

During hardware tests or operations, events occur at different absolute times and sequences vary in terms of duration, so it can be hard to make direct comparisons. Alignments solve this by defining a shared T-0 reference point for each Run, enabling direct comparison. A Family can have multiple alignments, and you can switch between them when visualizing Runs in Explore or configuring a Rule. You can align Runs to the following:
  • Run start or end: T-0 is set to the beginning or end of each Run. This works well for Runs with consistent structure.
  • A specific timestamp: T-0 is a fixed absolute time, useful when all Runs pass through a known moment.
  • An Annotation: T-0 is set when a named event occurs within each Run (such as an engine ignition or valve opening). This helps when the event happens at different absolute times across Runs. Annotations can be created manually or generated by Rules. You can align on these events, including derived events such as state transitions.

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Family statistics

Family statistics compute aggregate time series across all included members. When you save a Family statistic, Sift fetches data from each included Run in the configured time window, converts it to relative time using the alignment, and computes the aggregate at each time step. Supported aggregation types: Statistics can be scoped to specific time windows within a Run. For example, scoping for the 30 seconds after engine ignition only, using data ranges configured on the statistic.

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Family rules

Family rules use computed statistics as dynamic thresholds in rule expressions. A common pattern compares a Channel from a Run under test against a sigma band derived from the Family’s avg and stdev statistics. When evaluating a Family rule against a new Run, Sift prompts you to map the Run’s alignment configuration to the Family’s alignment so the comparison is time-synchronized correctly. Results appear in reports that show the Family statistic overlay alongside the Run’s Channel data in relative time.
Family Rules do not support live (real-time) evaluation. They are intended for retrospective analysis after a Run completes.

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Version history

Every change to a Family, including adding or removing members and updating alignments or statistics, creates a new version with a record of what changed and when. Version history is visible on the Family overview page and provides an audit trail of how the reference dataset changed over time.

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How-to guides