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Title: Learning sparse relational transition models

Paper content:
We present a representation for describing transition models in complex uncertain domains using relational rules.
For any action, a rule selects a set of relevant objects and computes a distribution over properties of just those objects in the resulting state given their properties in the previous state.
An iterative greedy algorithm is used to construct a set of deictic references that determine which objects are relevant in any given state.
Feed-forward neural networks are used to learn the transition distribution on the relevant objects' properties.
This strategy is demonstrated to be both more versatile and more sample efficient than learning a monolithic transition model in a simulated domain in which a robot pushes stacks of objects on a cluttered table.
Many complex domains are appropriately described in terms of sets of objects, properties of those objects, and relations among them.
We are interested in the problem of taking actions to change the state of such complex systems, in order to achieve some objective.
To do this, we require a transition model, which describes the system state that results from taking a particular action, given the previous system state.
In many important domains, ranging from interacting with physical objects to managing the operations of an airline, actions have localized effects: they may change the state of the object(s) being directly operated on, as well as some objects that are related to those objects in important ways, but will generally not affect the vast majority of other objects.In this paper, we present a strategy for learning state-transition models that embodies these assumptions.
We structure our model in terms of rules, each of which only depends on and affects the properties and relations among a small number of objects in the domain, and only very few of which may apply for characterizing the effects of any given action.
Our primary focus is on learning the kernel of a rule: that is, the set of objects that it depends on and affects.
At a moderate level of abstraction, most actions taken by an intentional system are inherently directly parametrized by at least one object that is being operated on: a robot pushes a block, an airport management system reschedules a flight, an automated assistant commits to a venue for a meeting.
It is clear that properties of these "direct" objects are likely to be relevant to predicting the action's effects and that some properties of these objects will be changed.
But how can we characterize which other objects, out of all the objects in a household or airline network, are relevant for prediction or likely to be affected?To
do so, we make use of the notion of a deictic reference. In
linguistics, a deictic (literally meaning "pointing") reference, is a way of naming an object in terms of its relationship to the current situation rather than in global terms. So
, "the object I am pushing," "all the objects on the table nearest me," and "the object on top of the object I am pushing" are all deictic references. This
style of reference was introduced as a representation strategy for AI systems by BID0 , under the name indexical-functional representations, for the purpose of compactly describing policies for a video-game agent, and has been in occasional use since then.We will learn a set of deictic references, for each rule, that characterize, relative to the object(s) being operated on, which other objects are relevant. Given
this set of relevant objects, the problem of describing the transition model on a large, variable-size domain, reduces to describing a transition model on fixed-length vectors characterizing the relevant objects and their properties and relations, which we represent and learn using standard feed-forward neural networks.Next, we briefly survey related work, describe the problem more formally, and then provide an algorithm for learning both the structure, in terms of deictic references, and parameters, in terms of neural networks, of a sparse relational transition model. We go
on to demonstrate this algorithm in a simulated robot-manipulation domain in which the robot pushes objects on a cluttered table.

assistant: text: A new approach that learns a representation for describing transition models in complex uncertaindomains using relational rules.