Layered/Hierarchical Pattern

• structure system to be decomposed into groups of subtasks, each of which is at a particular level of abstraction
• each layer provides services to the next higher layer

• generic application with 4 layers:
  • Presentation layer (also known as the UI layer)
  • Application layer (also known as the service layer)
  • Business logic layer (also known as the domain layer)
  • Data access layer (also known as persistence layer)
• OSI Model (e.g. TCP/IP Stack)

Client-Server Pattern

• consists of two parties; a server and multiple clients
  • server - listens to client requests
  • client - sends a request to the server

Master-Slave Pattern

• consists of two parties; a master and multiple slaves
  • master -

• database replication, the master database is regarded as the authoritative source, and the slave databases are synchronized to it

Pipe-Filter Pattern

• structure systems that process a stream of data
• pipe contains a sequence of filters, where each filter process the data before feeding it to the next filter

• Compilers. The consecutive filters perform lexical analysis, parsing, semantic analysis, and code generation.
• Workflows in bioinformatics

Peer-to-Peer Pattern

• individual components are known as peers
• peers may function both as a:
  • client, requesting services from other peers
  • server, providing services to other peers
• a peer may act as a client or as a server or as both, and it can change its role dynamically with time

• file-sharing networks such as Gnutella and G2
• multimedia protocols such as P2PTV and PDTP

Broker Pattern

• structure distributed systems with decoupled components
• broker component is responsible for the coordination of communication among components

• message broker software such as:
  • Apache ActiveMQ
  • Apache Kafka
  • RabbitMQ
  • JBoss Messaging

Event Bus Pattern

• 4 major components:
  • event source, event listener, channel, and event bus