User's guide chapter 10 section 1 & 2



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Chapter 10 – Modeling Techniques

10.1 – Activity-Related Techniques

10.1.2 – Activity Time Variation

Activity time that varies randomly due to the variable nature of the entity or activity or as a result of the inconsistent behavior of the resource used at the activity.

Suggested Technique

1. Determine the probability distribution that best fits the activity time (more on probability distributions).

2. Enter the probability distribution in the Time field of the General properties sheet for the activity (alternatively, a TIME statement can be used in the action logic for the activity).

Example: A phone-in order may have a time that is triangularly distributed with a minimum of 2 minutes, a mode of 5 minutes and a maximum of 12 minutes

Activity time variation example

TO DO: In the Time field of the General properties dialog enter T(2, 5, 12) as shown above. Alternatively you could enter Action Logic for the activity: TIME(T(2, 5, 12) min).

10.1.2 – Processing Entities Concurrently at an Activity

Multiple entities are allowed to enter an activity and be processed concurrently (at the same time at the same activity), independent of other entities.

Suggested Technique

1. Set the capacity of the activity to the maximum number of entities that can occupy the activity at any one time.

Example: Because a bank uses five tellers, the Bank_Teller activity is able to concurrently and independently handle up to five Customers at any given time.

Processing Entities Concurrently at an Activity

TO DO: Create the activity with a  Capacity of  5.

10.1.3 – Attribute-Dependent Activities

The activity time or some other activity action is based on the value of a particular attribute of the entity.

Suggested TechniqueAttribute-Dependent Activities

1. Define an attribute for the entity in the Insert -> Attributes & Variables dialog. Optionally, you may use one of the predefined attributes listed in Chapter 3.12.3.

2. Set the attribute to the desired value in any action logic in the model using the assignment statement.

3. Use an IF…THEN statement in the Action logic of the activity specifying the time or other action statements to be executed based on that attribute.

IF a_Type = REGULAR THEN
{
Time 8 Min
}
ELSE
{
Time 5 Min
}

Example: Two types of Orders are processed in a system: Regular and Pre-invoiced . At the Log In activity, Orders which have been previously designated as Regular orders require an invoice to be printed and therefore take 8 minutes to process. Pre-invoiced orders take only 6 minutes to process.

TO DO: Define a descriptive attribute called Type with the descriptors Regular and Pre Invoiced. Assign the appropriate descriptor to the attribute in some Action logic prior to the Log_In activity. Enter the Action Logic (as shown above) to determine the type of order and act accordingly.