Role properties dialogue

There are two advanced properties of role arrows that are set using this dialogue box. Note that it is not normally necessary or desirable to set these properties. They allow the program generation routines to make certain assumptions. If these assumptions are not valid, chaos will result.

Exclusive role

An exclusive role is one such as motherhood. Although each mother may have many children, each child has (or at some point had) exactly one mother. This is often expressed as a one-to-many relationship.

If you know there is always exactly one element in the list returned from the association submodel to the base model in this role, then you may (but do not need to) check the "Exclusive role" check box. The single element will then be returned by itself, without being enclosed in a list as would otherwise be the case. Note that in the aforementioned case of a motherhood relation, it would be the "is_child" role that is marked as exclusive, since the base model with the "child" role is getting the values from the unique association with a mother.

This allows you to use the value as an argument to functions such as element(). It may also be necessary to use this in conjunction with the property of influence arrows: "Use values made in same time step". It would probably help to talk about your model on the forum.

Allow base instance lookup

If you want to use one-sided relation enumeration, then the base model whose index you are looking up (as you loop over the instances of the other base model) has to be the one whose index is referred to as index(1) in the relation model. By default this would be the one with the role arrow that you added most recently, but it can be set using this property on its role arrow.

Since only one base model index can correspond to index(1) in the association submodel, setting this property on one role arrow clears it from other role arrows going to the same association submodel.

Setting this property never does any harm, and has other uses: if for some reason you have to delete one of your base models then re-create it, Simile might decide to change the order in which it assigns the index values in the association submodel, so what was previously index(1) becomes index(2). For this reason it's better to set variables in the base models to their indices and have influences from these into the association model (it also makes the equation more readable), but if you have referred directly to base model indices, setting this property allows you to control which base model index gets used as index(1).

Comments

Free-form comments can be entered in this text box, and are stored with the model. You are encouraged to comment your role arrows at length, so if you have used them wrongly, someone else can figure out how to put them right.

In: Contents >> Working with submodels >> Association submodels