# `prefix_span_pattern_miner`

PrefixSpan sequential pattern miner for sequence datasets. The library depends on the `sequential_pattern_mining_protocols` support library, implements the generic `pattern_miner_protocol` defined in the `pattern_mining_protocols` core library, and mines frequent sequential patterns using recursive projected databases with both same-event and next-event extensions.

Requires a dataset implementing `sequence_dataset_protocol` with sequences represented as ordered lists of canonical sorted itemsets over a declared item domain.

## API documentation

Open the ../../apis/library_index.html#prefix_span_pattern_miner link in a web browser.

## Loading

To load this library, load the `loader.lgt` file:

    | ?- logtalk_load(prefix_span_pattern_miner(loader)).

## Testing

To test this library predicates, load the `tester.lgt` file:

    | ?- logtalk_load(prefix_span_pattern_miner(tester)).

## Features

- Projected Database Mining: Mines sequential patterns by recursively projecting suffix databases.

- Itemset and Sequence Extensions: Supports both extending the last itemset and appending a new singleton itemset.

- Canonical Sequences: Validates that itemsets are sorted, duplicate-free, non-empty, and restricted to declared items.

- Flexible Support Thresholds: Supports minimum support specified either as a relative proportion or as an absolute count.

- Model Export: Mined pattern collections can be exported as predicate clauses or written to a file.

## Options

The `mine/3` predicate accepts the following options:

- `minimum_support/1`: Relative minimum support threshold in the interval `]0.0, 1.0]`. The default is `0.5`.

- `minimum_support_count/1`: Absolute minimum support count. When both support options are provided, this option takes precedence.

- `maximum_pattern_length/1`: Maximum total number of items in a mined sequential pattern. The default is `1000`, effectively capped by the longest sequence in the dataset.

- `minimum_pattern_length/1`: Minimum total number of items retained in the mined result. The default is `1`.

## Pattern miner representation

The mined pattern miner result is represented by a compound term with the functor chosen by the implementation and arity 3. For example:

    prefix_span_pattern_miner(ItemDomain, Patterns, Options)

Where:

- `ItemDomain`: Canonical sorted list of declared dataset items.

- `Patterns`: List of `sequence_pattern(Pattern, SupportCount)` terms ordered first by total item count and then lexicographically.

- `Options`: Effective mining options used to mine the frequent sequential patterns.

## References

1. Pei, J., Han, J., Mortazavi-Asl, B., et al. (2001) - “PrefixSpan: Mining sequential patterns efficiently by prefix-projected pattern growth”.