Types of input parameters

ADSM uses many parameters for scenario creation. Many are require and others are optional, depending on the details associated with each scenario. This section provides an overview of the types of parameters required to set up or alter a ADSM scenario.

General types

There are six general types of parameters used throughout ADSM: yes/no values, integer values, floating point numbers, probabilities, probability density functions, and relational functions. The user interface provides hints as to which type of value is required for each parameter, and will not allow users to enter the wrong type.

Yes/no values

Many scenario settings in ADSM may be switched on or off. Yes/no values (sometimes called true/false or boolean values) like this are usually set via check boxes: a check in the box indicates that the option will be enabled.

Integer values

Various parameters require whole number values. The user interface will not allow negative or floating point numbers in fields that require integers.

Floating point numbers

Floating point (sometimes called real) numbers are integer or non-integer values such as 1, 2.6, 9.34, etc. Several input parameters are floating point numbers.

Probabilities

Quite a few model parameters are specified as probabilities, or floating point values between 0 and 1. The user interface will not allow users to enter values outside of the range between 0 and 1 when a probability is required.

Probability density functions

Probability density functions (pdfs) are distributions of values representative of the natural range of possible values for some parameter. Values are drawn stochastically from these distributions as a simulation runs. See Probability Density Functions for information on entering and editing pdfs in ADSM.

Relational functions

Relationships or relational functions (rels) are used in situations where one variable is a function of another. See Relational Functions for information on creating and editing relational functions in ADSM.

Specific types

Units (herds or flocks)

The smallest unit in a ADSM scenario is a herd or flock. "Unit", "herd", and "flock" are used interchangeably in this guide.

Each unit has the following attributes, which must be specified by the user:

• Geolocation, specified by latitude and longitude
• Number of animals in the unit
• Production type
• Initial disease state

There are five disease states, as well as two more possible unit states that act somewhat like disease states.

Disease states

• Susceptible to infection
• Latently infected
• Infectious but not showing clinical signs of disease
• Infectious and showing clinical signs
• Naturally immune to infection

Additional states

• Vaccine immune to infection
• Destroyed

If a unit is not specifically assigned an initial disease state, it is assumed to be susceptible to disease. At least one unit in a scenario must be infected, with have an initial disease state of latent, subclinical, or clinical. If there is be no potential source of infection, and the simulation will not run.

Production types

Every unit in a simulation has a production type. A production type defines a group of herds with similar disease transmission probabilities, disease manifestation, disease detection probabilities, and control strategies. Production types are typically based on animal species and/or management practices applied to particular types of livestock operations.

Production types form the basis for many parameters in a ADSM scenario. Each production type has the following attributes:

• Duration of the latent, subclinical, clinical, and naturally immune disease stages (probability density functions)
• Duration of the vaccine immune stage (a probability density function)
• Detection and tracing parameters,(some of which are relational functions)
• Control measures, such as vaccination and destruction (some of which are relational functions)
• Direct costs associated with control measures

Production type pairs

Disease is spread from one unit to another based on contact rates and probabilities of disease transfer, which are set for each pair of production types. All disease spread parameters are set for pairs of production types in a scenario.