Landry (1983)

Question 1

The model-validating activities in Landry (1983)

Answer 1

The model-validating activities are grouped into 4 basis interrelated an iterative stages; 1) the problem situation, 2) the conceptual model, 3) the formal model and 4) the solutions and recommendations.

Question 2

The validation activities in Landry (1983)

Answer 2

Conceptual validation, logical validation and verification, experimental validation, operational validation, and data validation.

Question 3

Conceptual model Landry (1983)

Answer 3

The coherent “mental image” of the problem situation.
Formed by the perceptions and value judgements of both model builders and decision-makers
It is the way the problem situation is perceived and presented by modelers and users

Question 4

Formal model Landry (1983)

Answer 4

The translation of the conceptual model into mathematical symbols, or into computer languages à Developed to study the problem and/or to obtain solutions for formulations recommendations

Question 5

Solution Landry (1983)

Answer 5

The output of the modeling-validation process à obtained from the formal model using the solution techniques and procedures that are available

Question 6

Conceptual validation Landry(1983)

Answer 6

Iterative process between the problem situation and the conceptual model to validate to an acceptable level (may need to go back and forth several times until validity is achieved at an acceptable level)
Aims at answering:
- If one is looking at the problem situation from the appropriate perspective?
- Is the perspective susceptible to leading to appropriate solutions?
- To what extent are the constructs representative of the situation as perceived by the actors?
Main concern: The degree of relevance of the assumptions and theories underlying the conceptual model of the problem situation for the intended users and use of the model

Question 7

Logical validation Landry(1983)

Answer 7

Concerned with the capacity of the formal model to describe correctly and accurately the problem situation as defined in the conceptual model
Implies verifying whether any relevant variable or relationship has been omitted from the formal model
Checking whether the computer-based formal model is constructed as intended and as described in the conceptual model
A high level of logical validation does not imply a high level of conceptual validation

Question 8

Experimental validation Landry(1983)

Answer 8

Refers to the quality and efficiency of the solution mechanism used in the formal model → Experimental difficulties are removed through better solution techniques and experimental designs
Deals with the type of solutions obtainable from formal models with efficiency of obtaining the solutions, with the sensitivity of the solutions to changes in the values of the model’s parameters.

Question 9

Operational validation Landry(1983)

Answer 9

Determine the quality and applicability of the solutions and recommendations  Inform to help decisions-makers accept or reject the solutions and recommendations of the formal models to be implemented
Some difficulties occur during the implementation phase when solutions from the formal model are put to work → adaptions have to be made such as taking the omitted factors into account (removed to simplify the model)

Question 10

Data validation Landry(1983)

Answer 10

Concerned with the sufficiency, accuracy, appropriateness, and availability of the data (soft and hard) within acceptable cost limits.
Data is used in developing the conceptual and formal models, sensitivity analysis and in updating the model and its solutions.

Question 11

Three types of data according to Forrester Landry(1983)

Answer 11

1) Mental data bases: Instrumental in building the conceptual model
2) Written data bases: Instrumental in building the conceptual model
3) Numerical data bases: Used in finalizing the formal model