Indices | |

i , j | index of items, i, j = 1, ..., N |

o | index of orders, o = 1, ..., O |

m | index of pods, m = 1, ..., M |

Parameters | |

N | total number of items |

O | total number of orders |

M | total number of pods |

Q | number of inventory bins in one pod; Q=8 in this article |

B | number of inventory bins for the item i needed to be assigned |

S | similarity value between the item i and j, it is equal to the support count between item i and j |

S | item similarity matrix |

Decision variables | |

x | x |

x | |

y | number of inventory bins that item i occupies on the pod m |