Glossary
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READ FIRST! HOW TO ADD THINGS TO THE GLOSSARY (temporary readme, to be deleted once wiki is finalized!)
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- * (SIGMA function)
- Function that makes immediate event execution when placed on an edge.
A
- ASK{X}
- Displays the value of expression X during the run and allows you to change it.
- Attribute
- Characteristic of an entity.
- See also Systems.
B
- BET{X,Y}
- The SIGMA function for a beta distribution with shape parameters X and Y.
- Boolean variable
- A variable that equals 1 if it is true and 0 if it is false.
- Buffer
- The limited waiting space of a queue.
C
- Canceling edge
- An edge that cancels the event of the vertex it is pointing at. In SIGMA, a canceling edge by default is represented by a dashed line.
- See also edge.
- CLK
- Variable representing the current value of simulated time.
- Conditional edge
- An edge that requires a set of conditions to be satisfied before it can execute.
- See also edge.
- COS{X}
- SIGMA function for cosine of the input X.
D
- Dependent (Random variables)
- Two random variables are dependent if they are not independent
- Discrete event simulation
- Simulation of a discrete event system.
- See also Discrete Event System Modeling.
- Discrete Event System
- Systems where the status of the system changes at a particular instant of time.
- DISK{F,I}
- Reads the I-th number from disk file, F, where I is any valid integer-valued SIGMA expression. If I=0, the file is read sequentially. Data files can be read in any (random) order.
- See also Reading Data (and Code) from Your Disk.
- Do-loop
- TBA
E
- Edge
- An arrow between two vertices representing the relationship between those two events.
- EG
- Acronym for event graph.
- Empirical distribution
- A distribution computed from observed data.
- See also Using Empirical Input Distributions.
- Entity
- Articles whose interaction make up a system.
- See also resident entities and transient entities.
- See also Systems.
- English translation
- See automatic translation of SIGMA models.
- ERG
- Acronym for event relationship graph.
- Event
- A change in the state of the system.
- Event Canceling
- See Canceling Edge.
- Event graph
- A diagram that graphically captures the events taking place within a system and the relationships among these events.
- See also Event Graphs.
- Event relationship graph
- See event graph.
- ERL{X}
- SIGMA function for an Erlang distribution with parameter X.
F
- FIFO
- Acronym for "first in first out". Queueing methodology where the first entity to start service is the first entity to leave service.
- Future events list
- The master scheduler of events in a discrete event simulation that contains all of the events that are scheduled to occur in the future.
- See also Discrete Event Systems and Simulations.
G
- GET{OPTION;LIST}
- Removes a record from the specified LIST according to the OPTION chosen and places its contents in the ENT[] array.
- See also Using Ranked Lists.
- Graphics (Run mode)
- SIGMA Run Mode for which vertices and edges change color as the simulation progresses.
- See also Run Modes
H
- High Speed (Run mode)
- SIGMA Run Mode that bypasses the graphics in SIGMA and produces an output file.
- See also Run Modes
I
- Independent (Random variables)
- Two random variables are independent if and only if knowledge of the occurrence of any of these events has no effect on the probability of any other event.
- Initialization bias
- TBD
- See also Simultaneous Parallel Replications.
- Initialization condition
- Required user inputs necessary to start a simulation run
- See also Initial Attributes
J
- Just-In-Time
- See Just-In-Time compilation.
K
L
- LIFO
- Acronym for "last in first out". Queueing methodology where the last entity to start service is the first entity to leave service.
- LN{X}
- SIGMA function for the natural logarithm of an input X.
M
- Max{X,Y}
- Gives the maximum of expressions X and Y.
- Mean
- The arithmetic average of a set of numbers.
- MIN{X,Y}
- Gives the minimum of expressions X and Y.
- MOD{Y,X}
- Gives the integer remainder when the value of expression Y is divided by the value of expression X.
- Model
- A system used as a surrogate for another system.
N
- Node
- See vertex.
- NOR{X,Y}
- Sigma function for a normal distribution with mean X and variance Y.
O
- Option (PUT and GET)
- Option for how contents of ENT[] array are placed on the LIST for PUT or removed from the LIST for GET.
- See also Using Ranked Lists.
P
- Parameter (Event)
- A variable that describes certain characteristics of an entity and is passed as an attribute along edges between vertices.
- See also Event Parameters and Edge Attributes.
- Phantom Server
- A server created by simultaneously scheduled events.
- See also REWORK1.MOD.
- Priority (edge)
- Rank used to break time ties between events scheduled to occur at the same clock time.
- Priority (execution)
- See Priority (edge)
- Priority queue
- A queue where certain types of customers are given priority over other types.
- Process worldview
- A modeling philosophy where the focus is typically on transient entities.
- PUT
- Places the current contents of the ENT[] array in the LIST according to according to the OPTION chosen.
- See also Using Ranked Lists.
Q
- Queue
- A line of individuals waiting for service.
R
- Random number seed
- Five digit number required to generate a pseudo random number in SIGMA.
- See also Random Seed
- Reflexive edge
- TBD (not in the reader (?)
- Resident entity
- Entities that are inherent to the system. For example, workers in a car wash.
- Rework
- The need to process a job again due to a problem with the original processing.
- RND
- Variable representing a randomly chosen number between zero and one.
S
- SET{X}
- Sets all variables (including CLK) to zero and sets the random number seed to X; with no argument, the original stream continues.
- SIGMA
- Simulation Graphical Modeling and Analysis. ADD MORE HERE.
- Single step
- SIGMA tool that allows you to watch the simulation as each event is executed.
- See also The SIGMA Modeling Environment
- See also Run Modes
- SIN{X}
- SIGMA function for the sine of an input X.
- Size (of a variable in SIGMA)
- TBD.
- State (system)
- The state of a system is a complete description of the system and includes values of all attributes of entities, parameters of laws, factors for its policies, time, and what might be known about the future.
- State change
- A change in a state variable.
- State variable
- A variable that describes the state of the system being modeled.
- Step plot
- A type of Output Plot that shows the values of traced variables during a simulation run.
- See also Output Plot
- STS{X}
- Gives the area under the standardized time series for the traced variable X.
- See also Output Plot - Trend Detection
- System
- A collection of entities that interact with a common purpose according to sets of laws and policies.
T
- Tandem queue
- A queueing network where customers proceed through successive service operations along a single path.
- TAV{X}
- The time average of the traced variable, X.
- Time (simulation)
- TBD.
- Time average
- An average of taking into account how much simulated time the variable spends at a particular value.
- See also TAV{X}.
- Time sample variance
- TBD. (not in reader (?))
- Time series
- A sequence of data points, measured typically at successive times
- See also Standardized Time Series.
- Time tie
- Occurs when two events are scheduled to occur at the same time.
- Trace (simulation)
- A simulation where whenever a value for a random variable is needed by the simulation, it is read from a data file.
- See also Trace Driven Simulations.
- Trace variable
- State variables chosen to be recorded and displayed during a simulation run.
- See also Trace Variables.
- Transient entity
- Entities that enter into and depart from the system with relative frequency. For example, cars in a car wash.
U
- Unconditional edge
- An edge that tests the condition (1==1), which is always true, and therefore always executes.
- See also edge.
- Uniform distribution
- In SIGMA, a uniform distribution may be ADD MORE HERE!!
- See also uniform distribution.
- User (variable)
- TBD. (not really in reader, says it's "beyond the level intended for this documentation")
V
- Validation (modeling)
- INPUT DEFINITION FROM THE READER HERE.
- VAR{X}
- Cumulative variance for the traced variable X
- Variable
- TBD.
- Verification (modeling)
- The process of testing if the simulation is good.
- See also Model Verification.
- Vertex
- A node in an Event Graph representing an event.