Models and Systems Flashcards
Pidd (2010) definition of a system and its characteristics:
Boundaries. Some things are inside the system, others are not.
Components. More than a single element is contained within the boundary;
Internal organization. The elements are organized in some way;
Behavior. The system is recognized as a system because it has properties that belong to it as a system.”
Pidd (2010) definition of a human activity system:
- Open systems. There is communication and interaction across boundaries.
- Include human activity. What people do and why they do it are prime concerns.
- Include human intent.
- Have a limited life‐span.
- Self‐regulating. The system is maintained by a process of regulation, control or governance.”
Pidd (2010) describes how human activity system behaves:
- Norms are the expected (or normal) behaviour;
o At university it is expected that everyone contribute to the teaching - Values are the local standards used to judge people’s norms
- Structure contains the static aspects, e.g., physical environment;
o At a university it means who is in charge of what - Process is about how things are being done? What are people trying to do?;
o Education based on research – developing new ideas and methods - Climate is about how people value what they do? (the relationship between structure and process).
o Value knowledge and academic skills as well as freedom to perform activities
Roles in a system:
Problem owner: has certain interest in having the problem (dis-)solved
Client: The person whom the problem is solved for
Would-be problem solver: the one who decided that a situation should be addressed (often most supportive of a solution)
Graphical models are used for or as? Name some different models as well.
They are used as problem structural method (PSM)
- Rich picture
- Cause and effect diagram
What is another word for graphical models?
Conceptual models
Don’t confuse it with conceptual models in validation
Rich picture characteristics:
Are often used in the exploratory phase
Illustrate what is going on in a messy situation
Often contains styled parts and arrows showing connections between part in the mess
Good to present the current situation and guide the discussion on what to do
Cause and effect diagram characteristics:
Is used to assess what causes something else
A arrow denotes that concept A causes B
- Minus sign at the arrow means, that more of A causes less of B
Cause and effect diagram is hard to use in a human activity system because it is hard to predict human behavior
It makes a representation of what actions can be made (the bottom of the diagram)
- Change supplier, implement a formal inventory computer system etc.
This leads to intermediate concepts (actions) (the middle part)
- Change supplier can lead to having shorter lead times.
All end at the targets which we wish or do not wish to achieve (Top of the diagram)
- Achieving higher service levels or having higher inventory cost
Often used in SODA (strategic options development analysis (Pidd 2010)
- When used in SODA all concepts start with a verb
- Action oriented – what do we do, what happens then, what do you achieve.
Guidelines on building a conceptual model:
Make it clear what’s in the graphical /conceptual model. What does the arrows mean?
The conceptual model is there to clarify a mess, SO it should represent the mess, and not some subproblem in the mess
The mess contains the properties from Rosenhead (1996) such as multiple objectives and key uncertainties. If you identify these in the mess, include it in the conceptual model.
Be clear about the purpose of the conceptual model
The conceptual model should be validated
Hard modelling and soft modelling:
Hard modelling is the model developed like simulation, Arena or LP model.
Soft modelling is the problem structuring.
Often these will be used in a combination, but it is not always necessary to use the soft modelling, if you have a very clear problem and not a mess.
Soft modelling has an impact at the hard modelling
