Package eu.iv4xr.framework.mainConcepts

Class WorldModel

java.lang.Object
eu.iv4xr.framework.mainConcepts.WorldModel
All Implemented Interfaces:
Serializable
public class WorldModel extends Object implements Serializable
This describes a fragment of a virtual world in terms of how it is structurally populated by in-world entities. This fragment can represent what an agent currently sees. We can also use the same representation to represent the agent's belief on how the world is structured; this may incorporate its past knowledge which may no longer be up to date.
See Also:
Serialized Form

  • Field Details

    • agentId

      public String agentId
      The id of the agent that owns this World Model.

    • position

      public Vec3 position
      The position of the agent that owns this World Model.

    • velocity

      public Vec3 velocity

    • extent

      public Vec3 extent

    • timestamp

      public long timestamp
      Represent the last time this WorldModel is updated with fresh sampling. Note that sampling may only update the state of some of the entities, rather than all, because the agent can only see some part of the world.

    • elements

      public Map<String,​WorldEntity> elements
      In-world entities that populate this World Model.

  • Constructor Details

    • WorldModel

      public WorldModel()

  • Method Details

    • increaseTimeStamp

      public void increaseTimeStamp()
      Increase the time stamp by one unit.

    • getElement

      public WorldEntity getElement​(String id)
      Search a top-level entity with the given id. Note that this method does NOT search recursively in the set of sub-entities.

    • updateEntity

      public WorldEntity updateEntity​(WorldEntity e)
      This will add or update an entity e in this WorldModel. The entity can be an entity observed by the agent that owns the WorldModel, or it can also be information sent by another agent. IMPORTANT: this update may have some side effect on e itself, so e should be a fresh instance. In particular, if e is sent from another agent, it should be cloned first before it is sent. Case-1: a version ex of e is already in this WorldModel, its state will be updated with e if e's timestamp is more recent and if e's state is different. More specifically, this means that we replace ex with e, and then link ex as e's previous state. Case-2: e is more recent, but its state is the same as ex. We do not add e to the world model; we update ex' timestamp to that of e. Case-3: e is older than ex, but more recent than ex.previousState. In this case we replace ex.previousState with e. Case-4: e has no copy in this WorldModel. It will then be added. The method returns the Entity f which then represents e in the WorldModel. Note that e reflects some state change in the WorldModel if and only if the returned f = e (pointer equality).

    • mergeNewObservation

      public List<WorldEntity> mergeNewObservation​(WorldModel observation)
      This will merge a sampled (and more recent) observation (represented as another WorldModel) made by the agent into WorldModel. IMPORTANT: do not use this to merge WorldModel from other agents. Use instead updateEntity(eu.iv4xr.framework.mainConcepts.WorldEntity) for this purpose. Also note if an agent want to send information about an entity it knows to share it with another agent, it should send a copy of the entity as updateEntity(eu.iv4xr.framework.mainConcepts.WorldEntity) may have side effect on the entity. This method will basically add all entities in the new observation into this WorldModel. More precisely, if an entity e was not in this WorldModel, it will be added. But if e was already in the WorldModel, it will not be literally be added anew. Instead, we update e's state in the WorldModel to reflect the new information. The old state (so, the state before the update) will still be linked to the new state, just in case the agent needs it. Only one past-state will be stored though. The method will check if the given observation is at least as recent as this WorldModel. It fails if this is not the case. If the check passes, the the timestamp of this WorldModel will be updated to that of the observation. All entities that were added (so, all entities in observation) will get this new timestamp as well to reflect the fact that their states are freshly sampled. The method returns the list of entities that were identified as changing the state of this WorldModel (e.g. either because they are new or because their states are different). IMPORTANT: note that the implemented merging algorithm is additive. That is, it adds entities into the target WorldModel or updates existing ones, but it will NEVER REMOVE an entity. In theory this can be handled with some bit of reasoning, e.g. when the agent has an unobstructed line of sight to the entity, and the entity is within the agent's visibility range, but it is not present in the new observation, then we can conclude that the entity is no longer in the world, and hence can be removed from the WorldModel. Implementing this reasoning is still TODO.

    • mergeOldObservation

      public void mergeOldObservation​(WorldModel observation)
      This is used to merge an older observation into this one. E.g. it can be an observation sent by another agent.

    • isBlocking

      public boolean isBlocking​(WorldEntity e)
      A query method that checks whether the given entity can block movement. If so, it returns true, and else false. This method should be implemented by the subclass. So, override this.