DepotSafety
allocates drums to available storage space	StorageAllocation
applies depot safety policies during storage allocation

StorageAllocation
knows a kind of EPA hazard	Hazard
knows how many drums are assigned to a storage building	StorageBuilding
allocates drum storage to a storage building
applies drum storage safety policies during allocation
StorageAllocation class
produces prospective storage allocations
balances storage across prospective allocations

Building
knows a building identifier
knows its location within the depot (address)
knows its physical dimensions	Perimeter

Perimeter
knows an origin	Point
knows a boundary extent (width x depth)	Point
can expand itself by some interval
can determine whether it overlaps another perimeter

StorageBuilding extends Building
stores drums containing hazardous chemicals	DrumStorage
may only ever store two compatible hazard types

DrumStorage
has a storage license for a specific kind of hazard	StorageLicense
knows how many drums it can store (storage limit)
contains some drums	Drum
knows how many more drums it can store (remaining capacity)

StorageLicense
applies to a kind of EPA hazard	Hazard
applies to a specific storage building	StorageBuilding
knows a drum storage limit
StorageLicense class
maintains a license inventory (assets)
provides access to licenses by hazard

Hazard
identifies a kind of EPA hazard
Hazard class
provides access to the registered hazard types: 1, 2, 3

Drum
knows a drum identifier
contains a hazardous chemical	Chemical
knows its measurements	Weight
	Volume

Chemical
knows its name
knows a formula
knows its EPA hazard classification	Hazard
Chemical class
maintains a chemical registry
provides access to chemicals by name
provides access to chemicals by formula