Contents:

• Introduction
• Usage
• Examples
• Future Work

Introduction

The OAA/DAML Bridge agent allows for selected elements declared in DAML documents, such as classes and properties, to be accessed via the Open Agent Architecture.  This means that the selected elements are registered as "solvables" with an OAA facilitator, and thus may be queried, by OAA agents, using goal expressions in OAA's Interagent Communication Language (ICL).

Usage Synopsis

Under UNIX:

• oaadaml.csh [-create_synonyms] [-print_triples] URI

Under Windows (in a DOS shell):

• oaadaml.bat [-create_synonyms] [-print_triples] URI

Examples

The command

• oaadaml.csh http://www.daml.org/2001/03/daml+oil-ex.daml

causes the Bridge agent to load the contents of the given URI, connect to a facilitator, and register (with that facilitator) solvables corresponding to four types of DAML elements: fixed meta-classes, fixed meta-properties, "user-defined" classes, and "user-defined" properties.

Solvables

The fixed meta-classes and meta-properties are always the same (regardless of the DAML content), and are listed here.

For example, for the user-defined class Person (in http://www.daml.org/2001/03/daml+oil-ex.daml), the solvable

• 'http://www.daml.org/2001/03/daml+oil-ex.daml#Person'(Id)

is registered.  In addition, if the command line argument "-create_synonyms" is present, the solvable

• 'Person'(Id)

is also registered.  For the user-defined property hasParent, the solvables

• 'http://www.daml.org/2001/03/daml+oil-ex.daml#hasParent'(Id1, Id2)

and, when "-create_synonyms" is present,

• 'hasParent'(Id1, Id2)

are created.

Queries

As documented elsewhere, agents can query registered solvables by calling the library procedure oaa_Solve.

A query of a meta-class returns the (un-abbreviated) DAML identifiers of user-defined classes.  For example,
 

• 'Class'(X) returns with X bound to
• 'http://www.daml.org/2001/03/daml+oil-ex.daml#Animal'
• 'http://www.daml.org/2001/03/daml+oil-ex.daml#Person'
and so on.
 
A query of a meta-property also returns the (un-abbreviated) DAML identifiers of user-defined classes.  For example,
 
• 'SameClassAs'(X, Y) returns with
• X = 'http://www.daml.org/2001/03/daml+oil-ex.daml#Person'

Y = 'http://www.daml.org/2001/03/daml+oil-ex.daml#HumanBeing'
and so on.
 
A query of a user-defined class returns the DAML identifiers of user-defined instances.  For example,
 
• 'http://www.daml.org/2001/03/daml+oil-ex.daml#Person'(X) returns with X bound to
• 'http://www.daml.org/2001/03/daml+oil-ex.daml#Adam'
• 'http://www.daml.org/2001/03/daml+oil-ex.daml#Ian'
and so on.
 
A query of a user-defined property also returns the DAML identifiers of user-defined instances.  For example,
 
• 'http://www.daml.org/2001/03/daml+oil-ex.daml#age'(X, Y) returns with
• X = 'http://www.daml.org/2001/03/daml+oil-ex.daml#Adam'

Y = 37
• X = 'http://www.daml.org/2001/03/daml+oil-ex.daml#Peter'

Y = 46
and so on.

Source Code Organization

The OAA/DAML Bridge agent is a set of three classes grouped into a package called oaadaml. 
The three classes of the package are:
 
DamlOAA
This class is the starting point of the OAA/DAML Bridge runtime.  As it creates a jena model from the DAML input specified by the command line  loading all the triples  in that daml text, it creates solvables for the classes and properties defined in that ontology. After that it register these solvables into the facilitator.
 
DamlAgent
This class extends LibOaa and provides our daml agent with the ability to connecting to the facilitator.   It defines the appropriate actions to perform once a query matches with a registered solvable.   This code is given in the corresponding callback method.
 
DamlListener
This class defines the doOAAEvent method to be performed once a query matches with a defined solvable.

Future Work

• Allow a single instance of the Bridge agent to load in multiple DAML sites, rather than just one.
• Automatically load in ontologies that are referenced by import statements.
• Employ reasoning to provide more complete responses to queries involving meta-predicates such as sameClassAs (e.g., check transitivity) and uniqueProperty (check for unit cardinality on any property, not just those explicitly declared as uniqueProperty).
• When a query returns a construct such as <xsd.decimal rdf:value="9.5">, the Bridge agent should perhaps return just the value, rather than an anonymous object.
• In addition to the short forms of meta-classes and meta-properties (such as 'Class'(X) and range(Id1,Id1)), solvables should also be created using the fully qualified functors (such as 'http://www.w3.org/2000/01/rdf-schema#Class'(X)).

Copyright (c) 2001-2002 by SRI International