Distributed Systems Overview

Study Notes

Components communicate through message passing, which includes various communication models.

Applications: End-user software that relies on distributed resources.
Frameworks: Tools for distributed programming to simplify development.
Middleware: Software layer that facilitates communication and data management.
IPC Primitives: Interprocess communication tools for data control.
Operating System: Manages hardware and software resources.
Networking and Parallel Hardware: Infrastructure for data exchange and processing.

Banking Systems: Handle transactions across multiple locations.
Communication: Email services facilitating message exchange.
Distributed Information Systems: Includes the World Wide Web and federated databases.
Manufacturing Control: Systems for managing production processes.
Inventory Systems: Track goods and supplies across various locations.
General Purpose Applications: Used in educational institutions or office automation.

Client/Server Model: Centralizes information and services at a server accessed by multiple clients for resource efficiency.
Distributed Object Frameworks: Employs Remote Procedure Calls (RPC) for method invocations across networks. Key implementations include:
- CORBA: Common Object Request Broker Architecture.
- DCOM/COM+: Distributed Component Object Model.
- RMI: Remote Method Invocation.
- .NET Remoting: Allows .NET components to communicate across application domains.
Service Oriented Architecture: Utilizes web services for interaction between disparate services.

Extends procedure calls beyond a single process and memory space, enabling interaction between procedures on the same or different systems.

Extend object-oriented programming by allowing distribution across networks, while maintaining coherent operations.
Server Process: Maintains a registry of active objects for client access.
Client Process: Obtains references to remote active objects and invokes methods through these references, with parameters marshaled like in RPC.

SOAP Web Services:
- Based on the Simple Object Access Protocol, fully XML-based.
- Utilizes SOAP envelopes for secure communication.
- Standardized by W3C for greater security.
Restful Web Services:
- Architectural style rather than a protocol.
- Treats resources as identifiable entities with unique URIs.
- Supports diverse data formats, including XML and JSON.

XML: Standard for data representation and exchange.
SOAP: Protocol for structured message exchange.
UDDI: Universal Description, Discovery, and Integration for locating web services.
WSDL: Web Services Description Language, detailing service interfaces.
Example Implementation: A buyer links to a seller service via UDDI, with service definitions provided by WSDL.