1. Tutorial 6 Directory Facilitator
Fuhua Lin, PhD,
Professor, School of Computing and Information Systems
Athabasca University, Alberta, Canada
Nov. 7, 2009

2. Introduction
JADE implements a Directory Facilitator (DF) agent as specified by FIPA.
The DF is often compared to the "Yellow Pages" phone book.
Agents wishing to advertize their services register with the DF.
Visiting agents can then ask (search) the DF looking for agents which provide the services they desire David Grimshaw

3. DFAgentDescription
The DF is a centralized registry of entries which associate service descriptions to agent IDs.
The same basic data structure, the DFAgentDescription (DFD), is used both for adding an entry or searching for services. The difference is that when registering, you provide a complete description AND an AID; whereas when searching, you provide a partial description with no AID,
The search returns an array of complete entries (with AIDs) whose attributes match your description and you can extract the ID of suitable agents from those entries.

4. For agents to interact usefully in open systems, it is imperative that they use the same language conventions and the same vocabulary.
The DF entries thus concentrate on listing the ontologies, protocols and languages which are supported by the agents.
Additionally, entries have sets of services which are characterized by a name and name-value properties as well as the ontology/language/protocol conventions they support [seems a bit redundant...].

5. Below is the structure of a DF Agent description
Below is the structure of a DF Agent description. It appears quite complex, but most fields are optional and in actual practice we only need to use 1 or 2 attributes.
DFAgentDescription
Name: AID// Required for registration
Protocols: set of Strings Ontologies: set of
Strings Languages: set of Strings
Services: set of { {
{ Name: String // Required for each service specified
Type: String// Required ...
Owner: String
Protocols: set of Strings
Ontologies: set of Strings
Languages: set of Strings
Properties: set of
{ Name: String
Value: String } }

6. Please refer to: