Model Builder's Guide Chapter 7 - Revision history

Fei: /* ProbInit */

2006-09-27T22:16:09Z

ProbInit

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	Informal Specification: The preliminary expressions and main expression, pi(S), are evaluated for each cell in the initiation region InitRegion. The consequent expressions are only evaluated in those cells in which the event actually initiates – see NumClusters below.		Informal Specification: The preliminary expressions and main expression, pi(S), are evaluated for each cell in the initiation region InitRegion. The consequent expressions are only evaluated in those cells in which the event actually initiates – see NumClusters below.

	[[Image:~~Probinit~~.gif]]		[[Image:Chp7probinit.gif]]

	===NumClusters===		===NumClusters===

Fei: /* Property options and initiation/spread algorithms */

2006-09-27T21:20:18Z

Property options and initiation/spread algorithms

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	Table 5 Initiation/spread algorithms possible using options		Table 5 Initiation/spread algorithms possible using options

	~~'''TABLE MISSING'''~~		[[Image:Table5.gif]]

	NumClusters and NumRecipients can also be specified as a conditional. That is, rather than evaluating to a number (e.g. NUMCLUSTERS = 5), the keyword “WHILE” specifies that the expression is a condition rather than a number of cells to select, and that cells are to be chosen for initiation until that condition is false (or until all cells in EventLocation have been initiated). For example NUMCLUSTERS = WHILE numLeft > 0 will continue selecting cells for initation until numLess is <= 0 or every cell has been selected. Table 6 shows the additional initiation algorithms possible using a conditional number control.		NumClusters and NumRecipients can also be specified as a conditional. That is, rather than evaluating to a number (e.g. NUMCLUSTERS = 5), the keyword “WHILE” specifies that the expression is a condition rather than a number of cells to select, and that cells are to be chosen for initiation until that condition is false (or until all cells in EventLocation have been initiated). For example NUMCLUSTERS = WHILE numLeft > 0 will continue selecting cells for initation until numLess is <= 0 or every cell has been selected. Table 6 shows the additional initiation algorithms possible using a conditional number control.
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	Table 6 Initiation/spread algorithms possible using conditional “WHILE” option with NumClusters and NumRecipients and options.		Table 6 Initiation/spread algorithms possible using conditional “WHILE” option with NumClusters and NumRecipients and options.

	~~'''TABLE MISSING'''~~		[[Image:Table6.gif]]

	Hence a fairly large number different initiation/spread algorithms can be invoked by modifying whether ProbInit/NumClusters are specified, and the options specified.		Hence a fairly large number different initiation/spread algorithms can be invoked by modifying whether ProbInit/NumClusters are specified, and the options specified.

Fei: /* NumRecipients */

2006-09-27T21:13:39Z

NumRecipients

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	<u>Description</u>: Once SpreadProb has produced the “probability surface” SpreadProb, SpreadRecipients is evaluated to determine the actual number of cells to which the active cell should spread. The actual cells in which the event is initiated via spread are selected stochastically from the potential sites based on the probabilities in SpreadProb. For cells that initiate via spread, the consequent expressions for both SpreadRecipients and SpreadProb are evaluated. Once a cell has been spread to, initiation of the new active cell is handled by invoking Transitions, as for NumClusters, thereby cycling the event loop.		<u>Description</u>: Once SpreadProb has produced the “probability surface” SpreadProb, SpreadRecipients is evaluated to determine the actual number of cells to which the active cell should spread. The actual cells in which the event is initiated via spread are selected stochastically from the potential sites based on the probabilities in SpreadProb. For cells that initiate via spread, the consequent expressions for both SpreadRecipients and SpreadProb are evaluated. Once a cell has been spread to, initiation of the new active cell is handled by invoking Transitions, as for NumClusters, thereby cycling the event loop.

	~~'''FIGURE MISSING'''~~		[[Image:Numrecipients1.gif]]

	:If NumRecipients is not defined, then cells are selected for spread independently based on SpreadProb (i.e. the probabilities are absolute). For cells that initiate, the consequent expressions for SpreadProb are evaluated.		:If NumRecipients is not defined, then cells are selected for spread independently based on SpreadProb (i.e. the probabilities are absolute). For cells that initiate, the consequent expressions for SpreadProb are evaluated.

	~~'''FIGURE MISSING'''~~		[[Image:Numrecipients2.gif]]

	==Property options and initiation/spread algorithms==		==Property options and initiation/spread algorithms==

Fei: /* SpreadProb */

2006-09-27T21:10:14Z

SpreadProb

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	<u>Description</u>: After determining the spread location, the preliminary expressions and the main expression, sp(S), are evaluated for each cell in the spread region. The consequent expressions are only evaluated in those cells to which the active cell actually spreads – see NumRecipients below.		<u>Description</u>: After determining the spread location, the preliminary expressions and the main expression, sp(S), are evaluated for each cell in the spread region. The consequent expressions are only evaluated in those cells to which the active cell actually spreads – see NumRecipients below.

	~~'''FIGURE MISSING'''~~		[[Image:Spreadprob.gif]]

	===NumRecipients===		===NumRecipients===

Fei: /* SpreadLocation */

2006-09-27T21:08:33Z

SpreadLocation

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	<u>Description</u>: The set of cells returned by the region defines the landscape as seen during the spread of the active cell via SpreadProb and NumRecipients. Spreading only applies to this set of cells. The preliminary expressions are evaluated once before the main expression, while the consequent expressions are evaluated in each of the cells in the event region.		<u>Description</u>: The set of cells returned by the region defines the landscape as seen during the spread of the active cell via SpreadProb and NumRecipients. Spreading only applies to this set of cells. The preliminary expressions are evaluated once before the main expression, while the consequent expressions are evaluated in each of the cells in the event region.

	~~'''FIGURE MISSING'''~~		[[Image:Spreadlocation.gif]]

	===SpreadProb===		===SpreadProb===

Fei: /* Instantiation, Initiation and Spread of a SELES Landscape Event */

2006-09-27T21:06:40Z

Instantiation, Initiation and Spread of a SELES Landscape Event

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	Table 4 Value and default for main expression, and context of landscape event properties.		Table 4 Value and default for main expression, and context of landscape event properties.

	[[Image:~~Chap7table4~~.gif]]		[[Image:Chap7table402.gif]]

	An event instance is basically a dynamic activation of the LSE definition. Through initiation of clusters and spread, it acquires specific spatial locations at which it affects the landscape. Although the definition has a ReturnTime, an instance does not. It initiates clusters at the current clock time. It has a duration while active cells spread across the landscape, but it terminates when the last active cell, and hence the last active cluster terminates. The ReturnTime is used to schedule a new instance of an event.		An event instance is basically a dynamic activation of the LSE definition. Through initiation of clusters and spread, it acquires specific spatial locations at which it affects the landscape. Although the definition has a ReturnTime, an instance does not. It initiates clusters at the current clock time. It has a duration while active cells spread across the landscape, but it terminates when the last active cell, and hence the last active cluster terminates. The ReturnTime is used to schedule a new instance of an event.

Fei: /* ProbInit */

2006-09-27T21:01:30Z

ProbInit

← Older revision		Revision as of 21:01, 27 September 2006
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	Informal Specification: The preliminary expressions and main expression, pi(S), are evaluated for each cell in the initiation region InitRegion. The consequent expressions are only evaluated in those cells in which the event actually initiates – see NumClusters below.		Informal Specification: The preliminary expressions and main expression, pi(S), are evaluated for each cell in the initiation region InitRegion. The consequent expressions are only evaluated in those cells in which the event actually initiates – see NumClusters below.

	~~'''FIGURE MISSING'''~~		[[Image:Probinit.gif]]

	===NumClusters===		===NumClusters===

Fei: /* EventLocation */

2006-09-27T20:59:13Z

EventLocation

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	<u>Description</u>: The set of cells returned by this function defines the landscape as seen during the initiation of the event via ProbInit and NumClusters. Initiation only applies to this set of cells. The preliminary expressions are evaluated once before the main expression, while the consequent expressions are evaluated in each cell in the event region.		<u>Description</u>: The set of cells returned by this function defines the landscape as seen during the initiation of the event via ProbInit and NumClusters. Initiation only applies to this set of cells. The preliminary expressions are evaluated once before the main expression, while the consequent expressions are evaluated in each cell in the event region.

	~~'''FIGURE MISSING'''~~		[[Image:Eventlocation.gif]]

	===ProbInit===		===ProbInit===

Fei: /* SpreadTime */

2006-09-27T20:57:11Z

SpreadTime

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	<u>Description</u>: When an active cell occurs in a cell, the preliminary expressions are evaluated. The main expression is then evaluated to determine the length of time required for the event to spread to neighbouring cells. Spread from this active cell is scheduled on the event queue to occur at st(S) number of time units in the future. After the spreading is processed, the consequent expressions are evaluated and the active cell terminates.		<u>Description</u>: When an active cell occurs in a cell, the preliminary expressions are evaluated. The main expression is then evaluated to determine the length of time required for the event to spread to neighbouring cells. Spread from this active cell is scheduled on the event queue to occur at st(S) number of time units in the future. After the spreading is processed, the consequent expressions are evaluated and the active cell terminates.

	~~'''FIGURE MISSING'''~~		[[Image:Spreadtime.gif]]

	===SpreadLocation===		===SpreadLocation===

Fei: /* Transitions */

2006-09-27T20:51:40Z

Transitions

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	<u>Description</u>: When an active cell has initiated in a cell, either through event initiation or spread, the preliminary expressions and main expression, tr(S), are evaluated. If the <u>result</u> of tr(S) is TRUE (> 0), then the event occurs in the cell. The consequent expressions are only evaluated, and spreading is only attempted, if the event occurs. For spreading events, SpreadTime is invoked to schedule spreading.		<u>Description</u>: When an active cell has initiated in a cell, either through event initiation or spread, the preliminary expressions and main expression, tr(S), are evaluated. If the <u>result</u> of tr(S) is TRUE (> 0), then the event occurs in the cell. The consequent expressions are only evaluated, and spreading is only attempted, if the event occurs. For spreading events, SpreadTime is invoked to schedule spreading.

	~~'''FIGURE MISSING'''~~		[[Image:Transitions.gif]]

	===SpreadTime===		===SpreadTime===