Modeling the Zeus Knowledge Base

What is a knowledge base in Zeus?

A Zeus knowledge base is an ontology in Zeus vocabulary.  An ontology is a reservoir of  knowledge, usually attributed to some entity.  In Zeus, each defined agent must have some sort of ontology, which is a list of everything that it knows about in its universe.  An ontology is a definition of types, not of instances.  So, the 200 pianos that an agent has are not in its ontology, but instead the fact that an agent knows what a piano is.

What are the limitations of the Zeus ontology editor?

Zeus' ontology editor can be quite clumsy.  First of all, if several agents share certain facts (types), then one of two things must occur; either

1. Each agent must share the same ontology file, or

2. Each agent must duplicate the shared facts within their own respective ontology files.

The advantage of the second approach is that each agent will need only know about what it will deal with directly.  This is in keeping with the idea that an agent's ontology should be the list of everything that the agent should know about, and should not contain things with which the agent is not concerned.  With a universe with thousands of types, the ontology file could grow cumbersome, and performance would be be impacted.  However, the second approach is also error prone, and time consuming.  

Another limitation of Zeus' ontology editor is that multiple inheritance is not directly supported, but must be implemented through the laborious process of duplicating values (similar to approach 2 above).

What solution does Model Integrated Computing present?

Model Integrated Computing (MIC) allows for the definition of a graphical language to ease the creation and manipulation of ontology files.  The approach of the Knowledge Base Editor (KBE) paradigm (named ontology.edf in the GME world) was to allow for the creation of domains of knowledge.  Agents are also defined, and they are assigned domains as members of their ontology.  The interpreter writes out a Zeus compatible text file, that conforms to the Zeus ontology specifications.

The biggest benefit is that the code duplication which before was done by hand is now automated, which reduces error.  Secondary benefits are the introduction of a rapid development process, and also the ability to implement multiple inheritance.

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