dlp+vrml
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talk show tell print

intelligent agents

Visitors in virtual environments are often represented by so-called avatars. Wouldn't it be nice to have intelligent avatars that can show you around, and tell you more about the (virtual) world you're in.

Now, this is how the idea came up to merge the RIF project, which was about information retrieval, with the WASP project, another acronym, which stands for:

WASP


Web Agent Support Program

The WASP project aims at realizing intelligent services using both client-side and server-side agents, and possibly multiple agents. The technical vehicle for realizing agents is the language DLP, which stands for

DLP


Distributed Logic Programming

Merging the two projects required providing the full VRML EAI API in DLP, so thatDLP could be used for programming the dynamic aspects of VRML worlds.

background

Historically, the WASP project precedes the RIF project, but we started working on it after the RIF project had already started. Merging these two projects had more consequences than we could predict at the time. Summing up:

RIF + WASP


The major consequence is that we shifted focus with respect to programming the dynamcis of virtual environments. Instead of scripts (in Javascript), Java (through the EAI), and even C++ (to program blaxxun Community Server extensions), we introduced the distributed logic programming language DLP as a uniform computational platform. In particular, for programming inteligent agents a logic programming language is much more suited than any other language. All we had to do was merge DLP with VRML, which we did by lifting the Java EAI to DLP, so that function calls are available as built-ins in the logic programming language.

When experimenting with agents, and in particular communication between agents, we found that communication between agents may be used to maintain a shared state between multiple users. The idea is simple, for each user there is an agent that observes the world using its 'sensors' and that may change the world using its 'effectors'. When it is notified by some other agent (that is co-located with some other user) it can update its world, according to the notification. Enough background and ideas. Let's look at the prototypes that we developed.

multi-user soccer game

To demonstrate the viability of our approach we developed a multi-user soccer game, using the DLP+VRML platform.
We chose for this particular application because it offers us a range of challenges.

multi-user soccer game


Without going into detail, just imagine that you and some others wish to participate in a game, but there are no other players thatwant to join. No problem, we just add some intelligent agent football players. And they might as well be taken out when other (human) players announce themselves.

For each agent player, dependent on its role (which might be goal-keeper, defender, mid-fielder and forward), a simple coginitive loop is defined: sensing, thinking, acting. Based on the information the agent gets, which includes the agent's position, the location of the ball, and the location of the goal, the agents decides which action to take. This can be expressed rather succinctly as rules in the logic programming formalism, and also the actions can be effected using the built-in VRML functionality of DLP.

Basically, the VRML-related built-ins allow for obtaining and modifying the values of control points in the VRML world.

control points


These control points are in fact the identifiable nodes in the scenegraph (that is, technically, the nodes that have been given a name using the DEF construct).

This approach allows us to take an arbitrarily complex VRML world and manipulate it using the control points. On the other hand, there are also built-ins that allow for the creation of objects in VRML. In that case, we have much finer control from the logic programming language.

All in all we estimate that, in comparison with other approaches, programming such a game in DLP takes far less time than it would have taken using the basic programming capabilities of VRML.

agents in virtual environments

Let us analyse in somewhat more detail why agents in virtual environments may be useful. First of all, observe that the phrase agents in virtual environments has two shades of meaning:

agents in virtual environments


where ACL stands for Agent Communication Language. Our idea, basically is to use an ACL for realizing shared objects, such as for example the ball in the soccer game.

The general concept op multi-user virtual environments (in VRML) has been studied by the Living Worlds Working Group. Let's look at some definitions provided by this working group first. A scene is defined as a geometrically bounded, continuously navigable part of the world. Then, more specifically a world is defined as a collection of (linked) scenes.

Living Worlds


Now, multi-user virtual environments distinguish themselves from single-user virtual environments by allowing for so-called Shared Objects in scenes, that is objects that can be seen and interacted with by multiple independent users, simultaneously. This requires synchronization among multiple clients, which may either be realized through a server or through client-to-client communication.

Commonly, a distinction is made between a pilot object and a drone object.

Shared Object


So, generally speaking, pilot objects control drone objects. There are many ways to realize a pilot-drone replication scheme. We have chosen to use agent technology, and correspondingly we make a distinction between pilot agents, that control the state of a shared object, and drone agents, that merely replicate the state of a shared object. Since we have (for example in the soccer game) different types of shared objects, we make a further distinction between agents (for each of which there is a pilot and a drone version). So, we have object agents, which control a single shared object (like the soccerball). For these agents the pilot is at the server, and the drone is at the client. We further have agents that control the users' avatars, for which the pilot at user/client side, and the drone either at the server or the client. Finally, we have autonomous agents, like football players, with their own avatar. For those agents, the pilot is at the server, and the drones at the clients.

Now, this classification of agents gives us a setup that allows for the realization of shared objects in virtual environments in an efficient manner. See  [Community] for details.

The programming platform needed to implement our proposal must satisfy the following requirements.

programming platform


So, we adapted the distributed logic programming language DLP (which in its own right may be called an agent-oriented language avant la lettre), to include VRML capabilities. See the online reference to the AVID project for a further elaboration of these concepts.

PAMELA

 The WASP project's chief focus is to develop architectural support for web-aware (multi) agent systems. So, when we (finally) got started with the project we developed a taxonomy along the following dimensions:

taxonomy of agents


A classification along these dimensions results in a lattice, with as the most complex category a 3D-server-multi-agent system, of which the distributed soccer game is an example. See  [Taxonomy].

When we restrict ourselves to 3D-client-single-agent systems, we may think of,for example, navigation or presentation agents, that may help the user to roam around in the world, or that provide support for presenting the results of a query as objects in a 3D scene.

Our original demonstrator for the WASP project was an agent of the latter kind, with the nickname PAMELA, which is an acronym for:

PAMELA


Personal Assistent for Multimedia Electronic Archives

The PAMELA functional requirements included: autonomous and on-demand search capabilities, (user and system) modifiablepreferences, and multimedia presentation facilities.

It was, however, only later that we added the requirement that PAMELA should be able to live in 3D space.

In a similar way as the soccer players, PAMELA has control over objects in 3D space. PAMELA now also provides animation facilities for its avatar embodiment.

To realize the PAMELA representative, we studied how to effect facial animations and body movements following the Humanoid Animation Working Group proposal.

H-Anim


The H-Anim proposal lists a number of control points for (the representation of the) human body and face, that may be manipulated upto six degrees of freedom. Six degrees of freedom allows for movement and rotation along any of the X,Y,Z axes. In practice, movement and rotation for body and face control points will be constrained though.

presentation agent

 Now, just imagine how such an assistant could be of help in multimedia information retrieval.

presentation agent


Given any collection of results, PAMELA could design some spatial layout and select suitableobject types, including for example color-based relevance cues, to present the results in a scene. PAMELA could then navigate you through the scene, indicating the possible relevance of particular results.

persuasion games

But we could go one step further than this and, taking inspiration fromthe research field of persuasive technology, think about possible persuasion games we could play, using the (facial and body) animation facilities of PAMELA:

persuasion games


Just think of a news readerpresenting a hot news item. or a news reader trying to provoke a comment on some hot issue. Playing another trick on the PAMELA acronym, we could think of

PAMELA


Persuasive Agent with Multimedia Enlightened Arguments

I agree, this sounds too flashy for my taste as well. But, what this finale is meant to express is, simply, that I see it as a challenge to create such synthetic actors using the DLP+VRML platform.

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eliens@cs.vu.nl