1. ADAPTABLE SOFTWARE ARCHITECTURAL SOLUTIONS THAT ENABLE ADAPTATION
TO CHANGES IN REQUIREMENTS (MICROKERNEL)
BY DYNAMICAL CHANGE STRUCTURE AND BEHAVIOR OF SOFTWARE (REFLECTION)

2. MICROKERNEL PATTERN
SEPARATES a Minimal Functional Core (MICROKERNEL) from extended functionality provided by (INTERNAL SERVERS) and customer-specific parts (EXTERNAL SERVERS)
The MICROKERNEL also provides the sockets for plugging in these extensions and coordinating their collaboration.

3. EXAMPLE: FIPA Architecture
Describes :
Elements of FIPA agent systems
Relationships between elements
Mechanisms for communication and transport (communication languages, protocols, network services )
Addresses issues:
Transport mechanisms for messages(RMI, SUNIIOP)
Mapping specifications to new technologies (XML, CORBA, SMTP, web servers)
Levels of operation which include relationships between agents or between agents and platforms

4. FIPA-OS as Microkernel
Agent Shell
Agent Configuration
A.C.L.
Application Agents
Agent Management
Directory Facilitator
Task Management; Conversation Management
Message Transport Services; Internal Message Transport Protocols
Agent Communication Channel

5. INTELLIGENT AGENTS
“An intelligent agent is a software entity which exhibits, in some significant measure, autonomy, intelligence, and environmental awareness, and which interacts with its environment to achieve internal goals.” [Jennings, 1996]
Co-operation with other agents
Software + Hardware?
(Agents or Holons or Autonomous XXX?)

6. Architecture K n o w l e d g b a s Planner Scheduler Reasoning engine
Context collector
User profile manager
Context manager
Context parser
Content handler
Context dB
Message generator
ACL parser
Communications

7. reasoning, deciding and reacting component:
a protocol is a stereotypical dialogue for a cooperation framework (e.g. contract net)
reasoning, deciding and reacting component:
- maintains an agenda containing active scripts
- a script can be (goal-driven) invoked to satisfy an intention or (data-driven) involved in response to current situation
- a filter component which selects scripts to execute
4 December 2018
Multi-Agent Systems

8. WHY AGENTS ?
More usable and understandable structure (e.g. spaghetti code vs structure modules).
(Almost) essential in large distributed systems where all “subsystems” need to be continually interchanging information to collectively achieve or to maintain some desired state
(e.g. highly coupled subsystems)
(cf. human case of multi-disciplinary research team)

9. Dynamic Virtual Cluster
HOLONIC
ENTERPRISE
ENTERPRISE
Field
Cluster CC CC
RESOURCEr EC
RESOURCE EC CC CE CE CE
RESOURCE EC CE CE CE CC CC
RESOURCE
ENTERPRISE CE CE CE EC
RESOURCE EC CE CE CE CE CE CE CC CC
RESOURCEr EC
RESOURCE EC CC
Dynamic Virtual Cluster CE CE CE
RESOURCEr EC CE CE CE CE CE CE
Field
Cluster
HOLONIC ENTERPRISE AS A HOLARCHY

10. FIPA Kernel Includes mandatory agents that manage the platform:
AMS (Agent Management System) -- manages the creation,deletion,authentication of agents and provides a white pages directory service for the agents that reside on the platform
ACC (Agent Communication Channel)-provides the foundation for communication between the software agents
DF (Directory facilitator) represents a yellow pages directory for agents -has information about the agents and the services they offer.

11. Core Platform Functionality (FIPA - mK)
a collection of services that are closely coupled
provides an infrastructure where agents are deployed
a FIPA-compliant AP consists of three agents:AMS, ACC,DF

12. Agent Management System
Manages the platform resources
Has control over access and use of the AP being the managing authority of it.
Supports a set of methods for binding agents to platform, providing information about the platform capabilities and settings
Offers “white pages” services to other agents by maintaining an index of agent names that reside on an AP and their corresponding addresses.

13. Agent Communication Channel
The ACC is a low level entity that takes care of message routing between agents within an AP to agents on other APs.
It publishes its transport address into a file store to a location for other ACCs to locate
Uses information provided by the Agent Management System to direct messages between agents
Messages addressed to an agent will first be sent to an ACC.

14. FIPA-OS as Microkernel
Agent Shell
Agent Configuration
A.C.L.
Application Agents
Agent Management
Directory Facilitator
Task Management; Conversation Management
Message Transport Services; Internal Message Transport Protocols
Agent Communication Channel

15. Directory Facilitator
Provides a “yellow pages “ directory to agents
It must maintain an accurate list of agents with the most current information about them
Agents may register with DF or query it about types of services offered by other agents.
Management actions: register, search, modify

16. Message Transport Service
Provides the ability to send and receive messages to and from an Agent implementation
It has built-in mechanisms for Internal and External transport
It has a split structure composed of different service stacks (BufferService, ACCRouterService)

17. INTERNAL SERVER
Extends the functionality provided by the Microkernel (mK)
Encapsulate some system specifics
Design Rule: Keep the mK as small as possible
Extended services are activated by the mK as needed.
Example: Configuration server for agent profiles

18. FIPA-OS INTERNAL SERVERS
Agent configuration settings (in form of strings in a XML format)
Contains information or defines :
What MTP (message transport protocol) is used by the platform
Agent name
Address (location)
Types of databases to be used for storage
Profiles are read through parsers

19. INTERNAL VS. EXTERNAL Mandatory Functionality - INTERNAL SERVICES
Agent Shell
Task Manager
Conversation Manager
MTS
‘Pluggable’ Functions - EXTERNAL SERVICES
MTP
JESS (Agent Shell)
Parser’s (ACL, XML, RDF)

20. Agent Construction
FIPA provides a template (Agent Shell - internal service!) for building agents.
A new implemented agent consists of a class that:
extends the FIPAOSAgent class that provides methods for registration, message sending, setting up tasks and agent shutdown
contains a number of Task implementations that give the functionality of the agent
contains application specific code for the desired behavior within the architecture.

21. FIPA-OS as Microkernel
Agent Shell
Agent Configuration
A.C.L.
Application Agents
Agent Management
Directory Facilitator
Task Management; Conversation Management
Message Transport Services; Internal Message Transport Protocols
Agent Communication Channel

22. Agent Shell (IS) A template provided for agent implementation
Responsible for loading an agent profile and initializing its components
It creates a MTS (message transport service), a Task Manager and a Conversation Manager
A new agent consists of a class that extends the FIPAOSAgent and inherits all its methods among which we can find getProfile(), registerWithAMS(), shutdown()…

23. Agent Shell Provides functionalities (Policies) for: Sending messages
Retrieving the Agent’s properties
Registration with platform
Setting up the Task
Shutdown (clean shutdown for all components of an agent)

24. Task Manager (IS)
Splits the functionality of an Agent into small units of work (task decomposition)
The subtasks are reusable as code and easy to debug
Multiple tasks can be executed at once
Handles task creation and registration

25. FIPA-OS as Microkernel
Agent Shell
Agent Configuration
A.C.L.
Application Agents
Agent Management
Directory Facilitator
Task Management; Conversation Management
Message Transport Services; Internal Message Transport Protocols
Agent Communication Channel

26. Messages and Tasks
Multiple conversations can be conducted simultaneously given the ability of Task to send messages
A TaskManager coordinates the Tasks inside the agents and is built around event-based processing.
Every Task within the TaskManager has a set of events of type TaskEvent
When a new task is created (newTask()) an event will be added to the queue of the TaskEvent

27. Messages and Tasks (cont.)
If messages are constructed with the protocol field set to ‘fipa-request’, a certain message order is reinforced
Agents are configured to be able to handle all message types in that protocol
Messages sent are part of a Conversation and when a Task sends a message, the conversation that message is part of is bound to that Task.
In order to handle messages like request, refuse, inform, several methods that take Conversation objects as arguments are provided.

28. Constructing a Task public class FirstTask extends Task{
public FirstTask(OrderAgent owner){ }
public void startTask(){
public void sendRequest( Conversation conv ){
ACLMessage acl= getNewConversation(String protocol)
acl.setContent(…)
acl.setLanguage(…)
acl.setOntology(…)
forward(acl)

29. Tasks and Conversations
FIPAOSAgent
ConversationManager
TaskManager
MTS
Task
Conversation
FIPAQuery
protocol
TaskEvent
FIPARequest
protocol
ConversationUpdateEvent
public void handleRequest(conv)
Other Events

30. Conversation Manager (IS)
Provides the ability to track conversation state and mechanisms for grouping messages of the same conversation together (encapsulated as Conversation objects that represent individual conversations) - e.g. Cooperation Domains
Ensures that the conversation protocol is being followed by the involved parties (agents)
A Conversation class with various specializations is provided to enable the use of different protocols

31. Message Transport Protocol
Internal (RMI)
Proprietary mechanism
Efficiency vs. interoperability
Messages do not need to be prepared before being sent
External (SUNIIIOP)
Standardized mechanism
Provides interoperability
Messages are prepared before being sent

32. Interplatform communication

33. Message Encoding (ES)

34. Agent Languages
An agent language is a language for programming software or hardware agents or agent systems. It should provide for at least some structural agent features and may also allow agency attributes to be directly programmed. It may be incorporated in a development environment with user-friendly editors, browsers, etc. which facilitate the programming.
Most existing agent languages are deliberative (e.g. AGENTO, PLACA, CONCURRENT METAM, APRIL, MAIL) often related closely (or less so) to agent theory and logic. Some agent languages, e.g. ABLE, are reactive languages.
4 December 2018
Multi-Agent Systems

35. ACL Message structure
Represents a communicative act (Policy) that can be simple (inform ,request,confirm) or composed request(propose(action))
Has its corresponding semantics and protocol
Contains parameters=>attributes /values:
:language representation language for content
:content the information about which a message is sent
:receiver agent that receives the message
:protocol interaction protocol used by sender
ontology ontology to which the content refers to

36. Agent Interactions
FIPA ACL deals with intention interpretation and supports the communication between agents through explicit linguistic actions
The information content transmitted and the protocols are those described and defined in FIPA specifications

37. ACL - Example
The information content will be communicated through the existing message types.
Ex: (request
:sender OrderAgent
:receiver OperationPlanningAgent
:content(action d (produce 50 parts A (product ABC))(due date: Dec 12, 2000))
:protocol fipa-request
:reply-with order 132 )

38. Microkernel Implementation
1. Analyze the Application Domain (define policies of external servers; identify the core functionality needed to implement the external servers).
2. Categorize the services to separate core services (microkernel) from internal servers.
CRITERIA: time-critical, hardware-dependent and frequently used operations - in microkernel.

39. … cont
RULE: Place all resource-management services in the mK (e.g. agent management, task management, memory management). Also strategies for sharing, locking, allocation and de-allocation of resources.

40. APPLICATION DOMAIN: Supply Chain Management
Composed of cooperating agents, each performing a set of supply chain operations (functions: order, shipping, receiving, etc.)
The agents are constructed as computational systems that interact across networks
Agents are deployed on several FIPA platforms that already contain the infrastructure (mK) to enable the communication between them
The interactions among agents are managed through existing Task and Conversation classes (IS)

41. Agents for Supply Chain Roles and Interactions
Extending a generic agent framework to an integrated supply chain management architecture (by implementing new application specific agents) implies the identification of the entities involved in a supply chain as well as the elements that affect the performance of it.
Elements or roles like inventory control, material flows,information storage are embedded as abilities into new specialized agents or application specific agents which will perform the respective activities.
Other agents with built-in capabilities will model the roles played by different parts in a supply chain network such as capacity allocation, resource management and information exchange.

43. Agent Definitions Order Agent OperationPlanning Agent
- Gets orders from customers
- Handles requests for changing/ canceling orders
- Transmits the orders to OPAgent
OperationPlanning Agent
- Receives orders from Customer through the Order Agent
- Coordinates manufacturers, suppliers, transportation, distribution within the enterprise to achieve the best possible results in terms of customer requirements
- It monitors the execution of tasks through conversations with functional agents within the supply chain.

44. Agent Definitions (cont.)
Shipping Agent
- Schedules and monitors the performing of transportation tasks pertinent to each order as requested or specified by the OperationPlanning Agent
- Assigns transportation resources (routes) in order to construct the best possible shipping schedule.
Supplier Agent
- Responsible for scheduling the tasks related to product delivery
- Manages the availability of requested products

45. Agent Implementation
As part of the SCM architecture we consider some functional agents (Supplier and Shipping agents), the Operation Planning agent and an Order agent.
The information content transmitted and the protocols are those defined in FIPA language specifications

46. Implementation ...
4. Find a complete set of operations and abstractions needed to define every external service (POLICIES).
5. Implement each Policy using the services and mechanisms that the microkernel provides through its interfaces (includes services provided by internal servers).
Determine strategies for communication (request, transmission and retrieval of services)

47. Agent Construction
FIPA provides a template (Agent Shell) for building agents.
A new implemented agent consists of a class that:
extends the FIPAOSAgent class that provides methods for registration, message sending, setting up tasks and agent shutdown
contains a number of Task implementations that give the functionality of the agent
contains application specific code for the desired behavior within the architecture.

48. Agent Interactions
FIPA ACL deals with intention interpretation and supports the communication between agents through explicit linguistic actions
The information content transmitted and the protocols are those described and defined in FIPA specifications

49. Agent Interactions (cont..)
The information content will be communicated through the existing message types.
Ex: (request
:sender OrderAgent
:receiver OperationPlanningAgent
:content(action d (produce 50 parts A (product ABC))(due date: Dec 12, 2000))
:protocol fipa-request
:reply-with order 132 )

50. EXTERNAL SERVERS (‘Personality’)
Implement specific ‘views’ of the application domain (as Policies - e.g. Order Policy)

51. Agent Interactions (cont..)
The receiver (the OperationPlanningAgent) can only answer with agree, refuse in the first stage given the performatives for the fipa-request protocol employed here
(agree
:sender OperationPlanningAgent
:receiver OrderAgent
:content (produce d (50 parts A (product ABC)) (delivery time Jan 15, 2001))
:in-reply-to order 132
:protocol fipa-request
Request
Agree
Refuse
Inform
Failure

52. Messages and Tasks
Multiple conversations can be conducted simultaneously given the ability of Task to send messages
A TaskManager coordinates the Tasks inside the agents and is built around event-based processing.
Every Task within the TaskManager has a set of events of type TaskEvent
When a new task is created (newTask()) an event will be added to the queue of the TaskEvent

53. Messages and Tasks (cont.)
If messages are constructed with the protocol field set to fipa-request, a certain message order is reinforced
Agents are configured to be able to handle all message types in that protocol
Messages sent are part of a Conversation and when a Task sends a message, the conversation that message is part of is bound to that Task.
In order to handle messages like request, refuse, inform, several methods that take Conversation objects as arguments are provided.

54. Constructing a Task public class FirstTask extends Task{
public FirstTask(OrderAgent owner){ }
public void startTask(){
public void sendRequest( Conversation conv ){
ACLMessage acl= getNewConversation(String protocol)
acl.setContent(…)
acl.setLanguage(…)
acl.setOntology(…)
forward(acl)

55. Tasks and Conversations
FIPAOSAgent
ConversationManager
TaskManager
MTS
Task
Conversation
FIPAQuery
protocol
TaskEvent
FIPARequest
protocol
ConversationUpdateEvent
public void handleRequest(conv)
Other Events

56. Microkernel Implementation
1. Analyze the Application Domain (define policies of external servers; identify the core functionality needed to implement the external servers).
2. Categorize the services to separate core services (microkernel) from internal servers.
CRITERIA: time-critical, hardware-dependent and frequently used operations - in microkernel.

57. … cont
RULE: Place all resource-management services in the mK (e.g. agent management, task management, memory management). Also strategies for sharing, locking, allocation and de-allocation of resources.

58. Implementation...
7. Structure the Microkernel (e.g. using the Layers Pattern) to separate system-specific from system-independent parts. Lower layers hide system dependencies from the services that the Microkernel exposes publicly. Intermediate layers bridge hardware specifics with the gateways towards outside processes (the uppermost layer.)

59. Implementation ...
4. Find a complete set of operations and abstractions needed to define every external service (POLICIES).
5. Implement each Policy using the services and mechanisms that the microkernel provides through its interfaces (includes services provided by internal servers).
Determine strategies for communication (request, transmission and retrieval of services)

60. Agent Management System Agent Communication Channel
Layers
FIPA-OS Layers
Application Agents
ACL
MTP
Agent
Shell
Task/Conv.
Manager
Agent
Configurator
Directory
Facilitator
Agent Management System
MTS
Agent Communication Channel

61. FIPA-OS as Microkernel
Agent Shell
Agent Configuration
A.C.L.
Application Agents
Agent Management
Directory Facilitator
Task Management; Conversation Management
Message Transport Services; Internal Message Transport Protocols
Agent Communication Channel

62. …cont
Design and Implement the Internal Servers - they are accessed exclusively by the mK!!
Implement External Servers - write the Policies that describe the services such that they can be implemented using the programming interfaces of the mK.
Implement the Adapters - e.g. can be implemented as Proxies representing the external servers (one proxy per server).

63. REFLECTION PATTERN

65. PARTICIPANTS