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Operations Research Models and Methods
 
Computation Section
Markov Collection

The Markov Collection is a series of add-ins associated with Markov Processes. The Markov Process is a very general representation of time varying stochastic process. Additional discussion of this type of model are in the Models Section where articles discuss: Stochastic Processes, Discrete Time Markov Chains, and Continuous Time Markov Chains. Queuing is a class of Markov Models that allow closed form solutions. Simulation is a way to model and analyze more complicated stochastic systems. Although we have not included the Queuing or Simulation add-ins in this collection they are certainly relevant to the student/practitioner of stochastic processes. The Random Variables add-in may play a role in constructing models. The Inventory add-in describes an important application area.

The picture shows the ORMM menu when the add-in collection is installed. Each add-in has an individual role and can be operated independently from the rest. The Markov Data add-in calls the Markov Models add-in to construct models, and the Markov Models add-in calls the Markov Analysis or Markov Decision Process add-ins to obtain solutions.

This page provides brief introductions to the collection add-ins, Start and Finish commands that are common to the collection, and links to install the individual add-ins. Be sure to read the general instructions for installing and using add-ins before attempting to use them.

The first column on the table below has links to download the individual add-ins. The second column provides brief introductions. The titles link to more lengthy descriptions appearing elsewhere on this site. Click the Start/Finish link in the left margin to learn about adding and deleting buttons on pages. If you use any of the example worksheet pages you must learn to use this command.

Markov Data
This add-in builds constructs data forms and Markov models for specific problem classes. Models are provided for birth death processes and finite queues. Changing model parameters automatically adjust the model to reflect the changes. Large CTMC, DTMC and MDP models can be constructed with simple changes in parameter data. The Markov Data add-in calls the Markov Models add-in to construct the model forms.

Markov Models
This add-in builds models for Continuous Time and Discrete Time Markov processes, and also Markov Decision Process Models. The models are symbolic in that formulas are entered for transitions, transition rates, transition probabilities and other relevant components of a stochastic process model. The DTMC or CTMC models are constructed automatically. The models constructed are analyzed using the Markov Analysis add-in. Chapter 11, 12 and 14 in the ORMM book support this topic.

Markov Analysis
This add-in performs a variety of computations associated with DTMC (Markov Chains) and CTMC (Markov Processes) including: economic analysis, steady state analysis, computation of n-step probabilities, simulation, computation of first passage probabilities and computation of absorbing state probabilities. Chapters 13 and 15 in the ORMM book support this topic.

Markov Decision Process
A Markov Decision Process (MDP) adds decisions to Markov analysis . At each state there are two or more decision options that affect the costs and transition probabilities of the Markov chain. The system will operate the system in the least costly way if the operator chooses decisions indicated by the optimum policy. This add-in determines the optimum policy
Queuing
Although not included in the collection, the subject of queuing theory is important because it provides closed form equations for evaluating important special cases. The Queuing Add-in computes steady-state measures associated with Poisson queuing models, non Markovian queues and networks of queues. Both open and closed Markovian queues are modeled. The program also simulates multiple channel queues using two methods, a discrete next-event simulation and an entity simulation. An optimization feature is also included.
Simulation
Although not included in the collection the subject of simulation is necessary for complicated systems and when random variables are not governed by the Markov assumption. The Simulation add-in creates multiline simulations useful for analyzing a variety of systems that don't fit the model types handled by the other add-ins. The add-in builds and maintains worksheets on which simulations are easily built. Packaged models for time series simulation and inventory simulation are included. For most simulations, the RV add-in should also be installed.


  
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by Paul A. Jensen
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