Select the model for Group Communication

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Select the model for Group Communication

• Anna

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Motivation

• Group Communication Systems(GCS) have been
  exploited for many kinds of network-based
  applications,for example,collaborative
  computing,fault-tolerant distributed systems etc.
• The specifications of GCSs using natural
  language usually are ambiguous.
• Model is a solid foundation for
  Design,Analysis,Management of the given GCS.

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Methodology

• Analysis- concerned with understanding and
  modeling the application and the domain within
  which it operates. The output from analysis is a
  formal model that captures the three essential
  aspects of the system the objects and their
  relationships, the dynamic flow of control, and
  the functional transformation of data subject to
  constraints.
• Design - Defines the overall architecture of the
  system. Using the object model as a guide, the
  system is organized into subsystems. Decisions
  are made about inter-process communication, data
  storage, and implementation of the dynamic model.
  
• During the Object Design phase, the analysis
  models are elaborated, refined, and optimized to
  produce a practical design. Basic algorithms are
  chosen to implement each major function of the
  system, the structure of the object model is then
  optimized, the implementation of each association
  and attribute is determined.

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What is Group Communication?

• What is group?
• A group is a collection of processes that
  cooperate to provide a service
• Group Communication is a means for providing
  multi-point to multi-point communication, by
  organizing processes in groups.

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Key Attributes for Group Communication

• View a collection of related processes as a
  single abstraction.
• ordering capabilities, consensus on a common
  decision or reliable diffusion of messages.
• A message sent to the group is delivered to all
  members.
• The processes in the system share no global
  memory and communicate only by message passing
• Groups are dynamic
• Membership changes due to joins, departures or
  failures.
• Frequency of group creation/deletion.
• Related to network communication support
• Broadcasting
• Multicasting
• Unicasting
• Anycasting

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Group Communication primitives

• Message-passing between groups(processes)
• messages (or events) are expected for a given
  state of the protocol and trigger the messages
  passing and state transitions
• ?Group Membership Management?
• Interface
• Create/destroy process groups
• Add or withdraw a process to or from a group
• Provide failure detection
• Detector marks processes as suspected or
  unsuspected
• Notify members of group membership changes (due
  to add/withdraw/crash)

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Choosing Model

• Petri Net
• Message Sequence Charts(MSC)
• Finite State Model(FSM)
• Mathmatic Model
• Object-oriented Dynamic Model

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Specify Group Communication(1)

• Petri Net
• A Petri net is a graphical and mathematical
  modeling tool.
• Petri nets are a promising tool for describing
  and studying systems that are characterized as
  being concurrent, asynchronous, distributed,
  parallel, nondeterministic, and/or stochastic.
• Contrado not support data type and not scalable

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Specify Group Communication(2)

• MSC
• A Message Sequence Chart contains the description
  of the asynchronous communication between
  instances. The complete Message Sequence Chart
  language, in addition, has primitives for local
  actions, timers (set, reset and time-out),
  process creation, process stop and coregions.
  Furthermore sub Message Sequence Charts and
  conditions can be used to construct modular
  specifications.
• Most commonly used to depict exchange of messages
  and their processing between any number of
  entities both sequential and concurrent.

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Specify Group Communication(3)

• FSM
• most often are used to depict internal processing
  (change of states) influenced by incoming
  messages and/or events
• Pro Very expressive, allow hierarchy
• Contra doe not show message flow between
  entities, do not scale

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Which model can be used?

• Think about group? Sometimes we must treat it as
  an entity,sometimes have to think about the
  members in a given group.
• Petri-Net, MSC and FSM, each of them can not
  solve this problem.

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Object-oriented Model

• object model - via object diagrams, the object
  model specifies the static structure of objects
  and their relationships it is really the
  "cornerstone" of the technique, because it
  specifies what objects a system contains
• dynamic model - via state diagrams, the dynamic
  model specifies the aspects of a system which
  change over time, in other words, when objects
  change (like the old "flowcharts")
• functional model - via data flow diagrams, the
  functional model specifies the data value
  transformations (calculations) in a system, in
  other words, how objects change

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One of Object-oriented Model

• (M,O,D)
• Mset of Messages
• Oset of Objects
• Dset of Determination
• Notes
• Object every object has (State,Timer,Method).Sta
  tes can be set or gotten by the Methods. And
  every object maintain his own timestamp, and a
  table of the timers which belong to the other
  objects that communicate in moment with this
  object. A object can be a process or a group of
  process.
• Determination preconditions?actions
• Precondition have two types active and passive
  preconditions. Active means the Determination
  System collect the information which is necessary
  for it to determine Passive means the
  information are fed into the Determination.
• Passive like the sending or receiving the given
  Message
• Active like in a given time to collect the
  needed object-states.

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For Group communication

• Object a group or a single process
• Messages
• Determination
• Group communication
• Group Membership Management

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A Design for Multicast Group Membership
Management

• componets
• Group name administration
• Set management
• Delivery vehicle management
• Multicast transport service

Group membership management
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A Design for Multicast Group Membership Management

• Group Attributes
• GroupnameStruct-nameStruct-nameltRestrictgtStr
  uct-nameTrans-stemltTransientgtStruct-name
  Struct-nameName-segmentName-segmentltSeparato
  rgtStruct-name
• Typeltpublic,restricted,transientgt
• Group Leader
• Registrar
• Process Attributes
• Process id
• Transport address
• Groupname, maybe one or multi.
• Group agent

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A Design for Multicast Group Membership Management

• Determination
• Group Agentknows about and acts on behalf of the
  various TUP(transport user process)
• Group Leaderknows the membership of the entire
  set.It is determined dynamically for sets with
  public and restriced names,while for those with
  transient names,the agent at the node where the
  owner resides is the leader.
• Registrartwo basic functions
• Coordinate the leadership resolution process
• Direct the TUPs outside the multicast group to
  the group leader.

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A Design for Multicast Group Membership Management

• Messages
• Management Messages
• join-group ,leave_group(for public and restrict
  group)
• create_group,destory_group,add_to_group,delete_fro
  m_group(for transient group)
• query_group
• the other messages between agent,registrar,leader.
  
• Sequence

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Reference

• Multicast Group Membership Management Joshua
  Auerbach, Member, IEEE,etc
• Group Communication Specifications A
  Comprehensive Study,Gregory V. Chockler,The
  Hebrew University of Jerusalem Computer Science
  Institute,
• Distributed Algorithms, Lecture notes for the
  Graduate School IC,Prof. Andre Schiper
• A Dynamic Group Management Framework for
  Large-scale Distributed Event Monitoring, Ehab
  Al-Shaer
• T-79.186 Reactive Systems Introduction and
  Finite State
• Automata, Timo Latvala
• Reliable Research Towards Experimental Standards
  for Computer Science, Justin Zobel
• Simulation-based Test of Synchronous and
  Asynchronous Fault-tolerant Group Membership
  Services, Guillermo A.Alvarez
• An Object Model for Collaborative Systems and a
  Toolkit to Support Collaborative
• Activities, Haibin Zhu
• An Aspect-Based Object-Oriented Model for
  Multi-Agent Systems, Alessandro F. Garcia, Carlos
  J. P. de Lucena
• Introduction to OMT
• SERIES Z LANGUAGES AND GENERAL SOFTWARE ASPECTS
  FOR TELECOMMUNICATION SYSTEMS Formal description
  techniques (FDT) Message Sequence Chart
• Introductory Tutorial
• Petri Nets , Organised by Gianfranco Balbo