SHAKEN gpd 12170101

SHAKEN Roles

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Roles

SHAKEN divides the world into two major kinds of things: Entities ("things that are") and Events ("things that happen"). A Role represents an Entity's participation in an Event.

Here are some examples of Roles in SHAKEN.

You can see all the Roles currently defined in SHAKEN by expanding Role in SHAKEN's Browse window. Just click on the symbol next to 'Role':

      

Although Roles look like regular Entities, there are important differences:

  1. Many different kinds of Entities can play the same Role. For example, just about anything can be considered a Food, as long as some organism eats it.
  2. An Entity can play many different Roles, depending on what Events it participates in. For example, a Car can play the Role of Container, Product and Vehicle (the Role it is intended to play).
  3. An Entity can stop playing a Role, but it can't stop being an Entity. For example, you can use chewing gum as a Connector to attach two objects. It can stop playing the Role of Connector, but it can't stop being chewing gum.

How to Use Roles in SHAKEN

Roles can be added to concept maps, just like Entities and Events. They can be connected to Entities and Events using special relations. Usually there are three things involved in representing a Role: the Role itself, the Entity playing the Role and the Event in which the Entity is playing the role. For example, to encode the knowledge that a police car is being used as a barrier to block the road, you would say that the PoliceCar is playing the Role of Barrier in a Block (with a Road as object):

Note that if we had defined PoliceCar as a kind of Barrier, it would mean that police cars are a specific kind of Barrier -- not quite what we want.

Sometimes, however, there is such a strong association between an Entity and the Role it is intended to play that it is natural to say that the Entity is that Role. For example, a Fence is intended to be a Barrier. It is natural to say that a Fence is a Barrier (not just that Fences happen to be able to play the Role of Barrier). For such examples in SHAKEN we say that the purpose of a Fence is to be a Barrier in some Block:

Specifying the purpose of an Entity does not mean that it cannot play other Roles in other Events. The purpose of PoliceCar is to be a Vehicle, but it can play the Role of Barrier as well:


Defining Your Own Roles

As with Entities and Events, it's possible to define your own Roles in SHAKEN:
  1. Choose "Enter Knowledge" from SHAKEN's main menu
  2. then "Create a New Concept".
  3. Enter the name of the new Role and hit the "Continue" button.
  4. When prompted for "an existing concept to start from", type in Role (or a concept more specific than Role).
  5. Be sure to specify what kind of Entity plays your new Role (using the plays relationship), what Event is involved (using the in-event relationship) and what the relationship is between that Entity and the Event.

Here is an example of a newly defined Role. The Role is Student, which is a Role played by a Person in a Learn Event.


Is It a Role or an Entity?

It is not always obvious whether a given concept should be defined as a Role or simply as an Entity. Most new concepts you define will probably be Entities. Here is a simple test to help determine if your concept may be better encoded as a Role. For some new concept called "Flam":
  1. Can something be a Flam temporarily?
  2. Can something stop being a Flam (without ceasing to exist altogether)?
  3. Can something that isn't intended to be a Flam still be a Flam?

If the answer to these questions is "Yes", then "Flam" is probably a Role. Here are some examples to help distinguish Roles and Entities.

Role
Entity
Shelter
(a cardboard box can be a Shelter temporarily)
Cave
(something can't be a Cave temporarily)
Teacher
(you can stop being a Teacher)
Person
(if you "stop being a Person", you cease to exist)
Paper-Weight
(a Computer isn't intended to be a Paper-Weight, but it can still be used as one)
Rock
(something can't be a rock just because you intend it to be a rock)

Sometimes a particular Entity is so strongly associated with its intended Role (its purpose) that the two seem indistinguishable. Here is a trickier example: