You are here: Planning the Model > Steps for Doing Simulation > Step 2: Defining the System > Using Appropriate Data Sources
Having a specific set of questions for defining the system, we are now ready to search for the answers. Information seldom comes from a single source. It is usually the result of reviewing reports, conducting personal interviews, personal observation and making lots of assumptions. "It has been my experience," notes Carson (1986), "that for large-scale real systems, there is seldom any one individual who understands how the system works in sufficient detail to build an accurate simulation model. The modeler must be willing to be a bit of a detective to ferret out the necessary knowledge." Good sources of system data includes the following:
Predetermined Time Standards
Comparisons with Similar Operations
In deciding whether to use a particular source of data, it is important to consider the relevancy, reliability and accessibility of the source. If the information that a particular source can provide is irrelevant for the model being defined, then that source should not be consulted. What good is a maintenance report if it has already been decided that downtimes are not going to be included in the model? Reliability of the source will determine the validity of the model. A managers perception, for example, may not be as reliable as actual production logs. Finally, if the source is difficult to access, such as a visit to a similar facility in a remote site, it may have to be omitted.