TO USE OTHERS

1. Fundamental Problem
Essence of a “science”
 Observation
 Categorization/classification
 Abstraction
 Symbolic representation
 Manipulation
 Prediction

2. Solving the Problem
Creating a Reference Model
 Look for a reasonably small set of
organizing principles
 Propose reference model elements
 Check for consistency
 Refine
Reference models
are artifacts, not
natural phenomena

3. Engineering Examples
 Structural engineering, GTSTRDL, SAP
 Solid modeling, FEA
 Circuit design, SPICE, VHDL

4. Solving the Problem
Modeling principles for
developing a logistics reference
model:
• Observability
• Minimum inferred structure

5. Solving the Problem
Key (Observable) Warehouse
Elements
Warehouse Resources
Equipment
Entities: Labor Labor Equipment
Space
Customer
Goods Goods Orders
Orders
Customer Orders
Filled
Activities: changes to entities’ states

6. Solving the Problem
What CAN’T be observed?
Decision-making!

7. Solving the Problem
Hypothetical models of decision-
making
 Make a “theory” of decision making
 Make it as simple as possible, consistent with
observed effects of decision-making, but no
simpler
This does inferred structure
Minimum
not require
designing the control system.

8. Solving the Problem
Organizing Principle #1
• Warehousing resources and activities are
organized by departments
• Generic set of department types (or classes)
 Receiving  Sortation
 Transportation  Packing
 Storage  Shipping
 Fast picking  Value adding services

9. Solving the Problem
Generic Organization of
Resources
Department
Classes
Resource Types
Equipment Labor Space Product Order
Classes Class Class Class Class
Department
Set
Equipment Employees Space Product Order
Instances Instances Instances Instances
Resource Instances
Department
Instances

10. Solving the Problem
Object Models for Resources
 Trust me, it’s straightforward
 Even if it’s not unique

11. Solving the Problem
Organizing Principle #2
• Activities are organized into department-
specific tasks
• Generic set of task types (or classes)
 Receiving: Unload/receive  Fast picking: single order
 Transport: Put-away; pick; multiple order pick
retrieve; replenish  Sortation: sort
 Pallet Storage: Pick pallet;  Shipping: unitize pallet;
case pick to pallet pack & ship items; ship
pallet; load pallet

12. Solving the Problem
Organizing Principle #3
• Tasks correspond to flow in a functional
network
Inspection
Receiving Order picking
Bulk storage Shipping
Carton storage
Order sort/
• Handling unit conversions
and picking
accumulate • Processing options
• Total workload
Material flow Function-to-department mapping

13. Solving the Problem
Organizing Principle #4
• Warehousing tasks are composed from
fundamental warehouse operations
• Generic set of operation types (or classes)
 Move  Count
 Retrieve  Weigh
 Store  Measure
 Get  Scan
 Put  Communicate

14. Solving the Problem
Operation Reference Model
The associated operations reference model is simply:
do opn-ID using {res_ID} to {handling_unit_ID} from origin_loc_ID to dest_loc_ID
where:
opn-ID indicates what operation type to perform
{res_ID} indicates which resource(s) to use
{handling_unit_ID} indicates what is to be operated on, i.e., a container
or goods ID
origin_loc_ID indicates the starting location
dest_loc_ID indicates the ending location

15. Solving the Problem
Assertion
 The (time stamped) log of operations reports the
complete state trajectory of the warehouse

16. Solving the Problem
Generic Organization of
Operations
Task
Classes
Operation Types
Get/Put Store/Retrieve Move Count/Weigh/
Scan/Measure
Specific
Task Set
Transactions Transactions Transactions Transactions
Operation Instances
Task
Instance

17. Solving the Problem
Description ≠ Prediction
We can describe instances of resources
and operations or tasks.
We can log operations and summarize
historical state changes
But we still can’t predict behavior
Why?

18. Solving the Problem
Organizing Principle #5
Externa
Events
l
Messag
 Warehousing tasks/operations are event driven
Event
e
(comm n
Warehouse
Operat
State Data
r e of
and)
de c is io s e
io
d
ou
structure
Physical
Warehouse
n
I n fe rr e
s t ru ct u
This is aGenerator
THEORY,
s
Event Task
ma k in g
wa re h
pr oc e s
Monitor
not a model of any
specific WMS
Timer
Operation
Resources
Manager

19. Solving the Problem
Bad News and Good News
 Bad: Task generators are specific to the
warehouse design, because they are specific to a
department instance!
 Good: But there may be typical elements of task
generators

20. Solving the Problem
Location Assignment Decisions
 Truck to dock
 Product family to zone
 Goods to/from storage location
 Order to accumulation lane

21. Solving the Problem
Grouping/Partitioning Decisions
 Products to families
 Locations to zones
 Orders to waves
 Lines to zones/pickers

22. Solving the Problem
Sequencing/Routing Decisions
 Transport routing
 Pick sequencing/routing
 Retrieval sequencing
 Storage/retrieval interleaving

23. Solving the Problem
Is there an exhaustive class of
decision types just as there are
classes of resources and of tasks?
This would be a good thing!
What are the organizing principles?