Week 3 - Supply Chain Modelling Flashcards
What is a model
Is intended to represent a real system, either existing or planned
What are the major advantages of a model? (2)
• It succinctly represents the real system
• When investigated you are able to discover things about the real system
What is a system and it’s function? (2)
• Is a collection of interrelated components that work together towards a collective goal
• the function is to receive inputs and transform these into outputs
Name 3 characteristics of systems
• Environment
• Organisation
• Interdependency
Explain environment as a characteristic of systems
Systems are contained within an environment that contains other systems and external agencies and the scope of a system is defined by its boundary
Explain organisation as a characteristic of systems
The components of a system work towards a collective goal known as the system’s objective
Explain interdependency as a characteristic of a system
Systems are made up of subsystems (components) that may themselves being made up of other subsystems thus parts of a system are dependent on one another in some way
What is combinatorial complexity?
Is when we have activities that have a 2 way relationship with every other activity
How can the number of interconnections in combinatorial complexity be calculated?
n(n-1) where n is the number of activities
What is dynamic complexity?
Can arise in systems due to feedback and delays for example between cause and effect
What are the 2 main modelling methods?
• Descriptive modelling
• Explanatory modelling
What is descriptive modelling? (2)
• Based on measuring observed behaviour
• If a system shows a certain regularity in behaviour then future behaviour may be predicted under the same conditions
Name some examples of descriptive modelling (3)
• Regression analysis
• Data mining
• Machine learning
What is explanatory modelling? (2)
• is based on a systems view and represents the real system structure
• It emphasises on the identification on the processes that are decisive for system behaviour
What is a deterministic model?
Is a model that does not represent uncertainty and so for a given set of conditions and parameters will always produce the same outcome
What does a deterministic model imply?
It implies that given a well enough detailed snapshot of a system we should be able to forecast the system’s dynamic behaviour perfectly thus are able to be analytically traceable and expressed as a mathematical formulae
What does a stochastic model include? (2)
Includes some random component such as:
• variable demand rate
• variation or processing rates due to natural variability
Benefit and drawback of stochastic models
• Models have an increased realism (benefit)
• (Drawback) make even simple models intractable
3 Examples of static models
• Linear programming
• Spreadsheets
• Monte Carlo simulation
How should models be developed? (According to Pidd 2009 applying the principles of Occam’s razor 1300)
Developed so that they are as simple as possible and yet are valid and useful for their intended purpose
What are the general principles for model development? (4) (Robinson van der zee 2018)
• Focus on the decision, not the system
• Abstract - do not model all you know about the world
• The model should drive the data requirements and not the available data drive the model
• start small and add
What is required when starting a simple model? (Brooks and Tobias 2000)
Requires us to define a number of simplifications to define what simple model
What is a puzzle? (Pidd 2009)
Is a set of circumstances in which there is no ambiguity whatsoever once so,e thought has been given to what is happening or needs to be done
What are the issues that need to be faced with puzzles? (3)
• entirely clear
• the range of options being completely known
• a single correct solution