It is not expected that the server or remote partner must be “always available”

Clients are highly dependent of the server location, implementation language, state and availability

Important number of demands, processing, memory or networking resources limits can be encountered

Performance and reliability of the distributed system can get compromised

A distributed system can be split in several tiers or components

Client side (client-tier), server side (presentation-tier), the application logic (business-tier) and enterprise information system (EIS-tier)

Allows an application to execute a procedure or operation offered by a remote system

RPC implementations are based on the synchronous request-reply pattern that

Allows the communication with remote objects while hiding networking mechanisms

At the client side a proxy allows accessing the object methods by implementing the required networking-oriented operations

Offers asynchronous communication between distributed applications

Messages contain network routing information and the payload allowing communication

Queues represent mediators assuring asynchronous communication

Provide adapted solutions to cope with the heterogeneity nature of infrastructures

How people, organizations and systems provide and use services in an agile, scalable and interoperable world

Service implementation: a physical implementation of the service providing the required capability or business logic

Service repository: provides the required facilities to discover and use services

Service bus: provides the required connectivity between the service participants

Service contract: formal or informal specification of the service

NOTE: a service is accessed using the service interface and the resulting service has to be consistent with the service description or contract

A technological style aimed at providing in a flexible and easier way hardware or software-computing resources as services

Consists in providing to cloud consumers applications and / or software to process business functions

Consists in providing to cloud consumers platforms that allows them developing, deploying and hosting their own applications and software

Consists in providing to cloud consumers infrastructural resources (storage, computing, network) usable for deploying and running their own platforms, applications and software

The automation that allows supporting all the cloud operations in an efficient and scalable way with a minimum human intervention

The ability to virtualize all resources (infrastructure, platform, application) in order to offer them as a service

A cloud consumer can provision, use and release resources based on its needs and these operations don’t require intervention at the provider side

A cloud consumer can access to providers’ resources and services using any kind of devices connected to the Internet.

A cloud provider applies multi-tenant models to pool its resources to serve multiple cloud consumers

This operation allows providers using better their resources and need to be transparent for consumer

A consumer can access to the services at any time, as they have an unlimited capacity

At the provider side, this requires an adaptation of the underlying resources and a dynamic allocation according to the load and the number of consumers

Resource usage can be monitored, controlled, and reported, providing transparency for both the provider and consumer of the used service

Cloud systems automatically control and optimize resource usage by leveraging a metering capability at some level of abstraction appropriate to the type of service