Dot notation is to call the method as we do it by using space. we can call methods by using space with all variables but dot notation is used with property and synthesizes variables only
example
variable.method_name; //is a dot notation with property and synthesized variable
[variable method_name]; // is space notation
and the dot notation is for all default properties because those are already property and synthesized like
label.text = @"Ashok";
and as said space can be used by synthesizing separately using set method as
[label setText:@"Ashok"];
ThanQ