diff --git a/lua/PredatorPrey.lua b/lua/PredatorPrey.lua
index 180f8cf..f712ddc 100644
--- a/lua/PredatorPrey.lua
+++ b/lua/PredatorPrey.lua
@@ -1,6 +1,6 @@
 --- Model that implements predatory-prey dynamics.
--- @arg data.wolves A number between 10 and 40 with the initial number of wolfes.
--- @arg data.rabbits A number between 100 and 1000 with the initial number of rabbits.
+-- @arg data.predator A number between 10 and 40 with the initial number of predators.
+-- @arg data.prey A number between 100 and 1000 with the initial number of preys.
 -- @arg data.preyGrowth A number between 0.01 and 1 with the probability of a prey
 -- to reproduce. The default value is 0.08.
 -- @arg data.preyDeathPred A number between 0.0001 and 0.01 with the probability of a prey
@@ -11,36 +11,40 @@
 -- predator population per eack prey killed. The default value is 0.00002.
 -- @arg data.finalTime The final time of the simulation. The minimum value is 50 and the
 -- default value is 500.
+-- @arg data.period The time interval where the number of predators and preys are updated.
+-- The observation of the model occurs at one time step, therefore if this value is 0.1 then
+-- it will update the populations ten times for each update in the charts.
 -- @image predator-prey.bmp
 PredatorPrey = Model{
-	wolves          = Choice{min = 10,                 default = 40},
-	rabbits         = Choice{min = 100,                default = 1000},
-	preyGrowth      = Choice{min = 0.01,   max = 1,    default = 0.08},
-	preyDeathPred   = Choice{min = 0.0001, max = 0.01, default = 0.001},
-	predDeath       = Choice{min = 0.001,  max = 0.5,  default = 0.02},
-	predGrowthKills = Choice{min = 0,      max = 0.01, default = 0.00002},
-	finalTime       = Choice{min = 50,                 default = 500},
+	predator        = Choice{min = 1,                   default = 40},
+	prey            = Choice{min = 1,                   default = 1000},
+	preyGrowth      = Choice{min = 0.000001, max = 1,   default = 0.08},
+	preyDeathPred   = Choice{min = 0.000001, max = 0.5, default = 0.001},
+	predDeath       = Choice{min = 0.000001, max = 0.5, default = 0.02},
+	predGrowthKills = Choice{min = 0,        max = 0.5, default = 0.00002},
+	finalTime       = Choice{min = 5,                   default = 500},
+	period          = Choice{min = 0.0001,              default = 1},
 	execute = function(model)
-		model.rabbits = model.rabbits + model.preyGrowth * model.rabbits
-		                - model.preyDeathPred * model.rabbits * model.wolves
+		model.prey = model.prey + model.preyGrowth * model.prey
+		                - model.preyDeathPred * model.prey * model.predator
 
-		model.wolves = model.wolves - model.predDeath * model.wolves
-		              + model.predGrowthKills * model.rabbits * model.wolves
+		model.predator = model.predator - model.predDeath * model.predator
+		              + model.predGrowthKills * model.prey * model.predator
 	end,
 	init = function(model)
 		model.chart1 = Chart{
 			target = model,
-			select = {"rabbits", "wolves"}
+			select = {"prey", "predator"}
 		}
 	
 		model.chart2 = Chart{
 			target = model,
-			select = "wolves",
-			xAxis = "rabbits"
+			select = "predator",
+			xAxis = "prey"
 		}
 
 		model.timer = Timer{
-			Event{action = model},
+			Event{action = model, period = model.period},
 			Event{action = model.chart1},
 			Event{action = model.chart2}
 		}