The document describes the Gathering pattern, which is an adaptation pattern for multi-agent systems. The Gathering pattern triggers the formation of an initiative by facilitating a casual meeting of agents at a shared "venue," allowing them to begin interacting and coordinating without prior knowledge of each other. Once an initiative is created, it can then evolve into a more established organizational structure through additional adaptation patterns. Adaptation patterns provide attractors that help self-organize agents to form emergent, adaptive architectures.

1. ADAPTATION PATTERNS
IN MULTI-AGENT
ARCHITECTURES:
THE GATHERING PATTERN
J. Santiago Pérez-Sotelo, CETINIA, URJC
Carlos E. Cuesta, VorTIC3, URJC
Sascha Ossowski, CETINIA, URJC
Hersonissos, Greece, 18/10/2011

2. CONTENTS
 Introduction
 Lifecycleof Self-Organising Architectures
 Adaptation Patterns
 The Gathering Pattern
 Conclusions
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3. INTRODUCTION
 Current software systems keep growing both in
complexity and size
 New strategies required to handle this complexity
 Self-adaptation: let’s let systems to do routine task
themselves
 Many architectural levels to consider
 Potential benefits include scalability
 Multi-Agent Systems (MAS)
 A general problem-solving strategy
 Adding organisations to provide further structuring
 Adding adaptive support to increase flexibility
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 Agreement Technologies: the next step

4. LIFECYCLE OF A SELF-ORGANISING
ARCHITECTURE (I)
 The goal is to provide adaptive organisations
 With an emphasis on coordination mechanisms
 These are created as self-organising architectures
 Achieved by creating emergent agreements
 Any structure is created by combining controls and
protocols
 Controls: enforce or forbid some interaction
 Protocols: enable or channel behavior
 In a self-organising structure, agents arrange
“semi”-spontaneously in an “elemental” group
 This will be known as an initiative
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 The first step on an emergent agreement

5. LIFECYCLE OF A SELF-ORGANISING
ARCHITECTURE (II)
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6. LIFECYCLE OF A SELF-ORGANISING
ARCHITECTURE (III)
 Sets of controls & protocols are arranged into
specific patterns
 Groups of agents match these patterns, arranging in a
preliminary structure
 Initiative: an initial group, which is growing
 Organisation: an established group, which provides
specific services (just like any agent)
 Agreement: the act which transforms an initiative into an
organisation
 These specific patterns are designed to deal with
external adaptation issues
 Hence they are called adaptation patterns 6

7. ADAPTATION PATTERNS
 Provide an “attractor” trying to “capture” agents into
a developing structure
 It either creates or (re)shapes an initiative
 They are architectural patterns
 In an agent-based, service-oriented architecture
 Services “guide” the definition of an organisation
 Defines both a structural and behavioural perspective
 Two kinds of “special” agents appear
 Shifter: an agent which changes
 It shifts its own interface and behavior
 Changent: an agent of change
 It induces changes on others
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8. THE GATHERING PATTERN (I)
 A similar structure of “standard” patterns
 Just like other adaptation patterns
 Has a significant role on a basic “family” of patterns
(“emergent organisation”)
 A notion similar to a pattern language
 Several different pattern languages can compete /
collaborate for the same set of agents
 Gathering: the pattern which triggers the formation
of an initiative
 A “casual” meeting of agents starts to evolve to
compose an emergent organisation
 Uses a self-organising approach 8

9. THE GATHERING PATTERN (II): STRUCTURE
 Name: Gathering
 Classification: Creational
 Intent: Monitors the space, routing information and
promoting coordination
 Context: There is no initiative yet: agents don’t
know each other but should begin interaction
 Motivation: To evolve from a simple “set” of agents
to create a service ecosystem
 Participants:
 Two (or more) agents shifters
 A venue (a “gathering place”) the changent 9

10. THE GATHERING PATTERN (III): PROTOCOL
 The -calculus specification comprises three
abstractions (processes)
 AgentX: behaviour of any agent
 First, it wakes and it asks where it is
 After event, it identifies and provides a return channel
 It receives the name of another agent, they can interact
 Repeat that indefinitely
 Venue: the gathering place where agents meet
 First, it defines itself as a place to register
 Once more than one agent has registered, it triggers an event
(of course this can be modified)
 The event is used to “broadcast” the name and channel of
every agent to the rest of them 10
 Subsystem: serves as the connector in this case

11. CONCLUSIONS
 The gathering provides one among many ways to
initiate the communication between agents who
were initially unaware of each other
 Once the initiative has been created, it can evolve in
many ways to define an organization
 Many other adaptation patterns in charge of this
 Surveyor Election, Surveyor, Facade, etc.
 Protocols might use a different language
 These organisations provide coordination
 This is the evolution of agreements, which are also
understood as the evolution of MAS
 This approach is still under development
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 Adaptive architectures seem already feasible

12. THANKS FOR YOUR ATTENTION
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