Client-Server

A paradigm where providers of resources are designated as servers, and the resource requesters are the client.

Servers are passive and listen (wait) for incoming requests. When a request is received the server will respond with the resources needed

Service that makes the request. Client process makes a request and will wait for a response

Refers to any operations that happens on the client side

It offloads processing to the client Reduces load on server and reduces the communication bandwidth

Can pose a security risk

Refers to operations that happens on the server

As it gives more control over the environment in which the scripts are executed. Scripts are hidden on the server Server can be optimised to cope with heavy processing demands

A set of functions and protocols the client can use

An API for establishing a persistent TCP socket connection

Create Retrieve Update Delete

Create - writes a record to a database Retrieve - Gets a record from a database Update - amends a record Delete - removes a record from the database

A database management system As multiple clients can update a database with only one copy of the database existing the DBMS will handle the requests.

Record Locks Serialisation Timestamp ordering Commitment ordering

When a user wants to update a record, the record is locked for the duration of the update

Transactions can only happen one at a time and the DBMS handles the order

When a record is read its read timestamp is updated Before record is written back, the DBMS will check the timestamp If the timestamp has been changed then it will be cancelled

Transactions from multiple clients, and the timestamps are all sent to the server. The server creates a queue, using timestamps, and processes them in a FIFO manner

It is the application-layer protocol used to communicate between web servers and browsers

POST GET PUT DELETE

Representational State Transfer An architectural style that determines how systems communicate

Allow client and server to be programmed independently while still able to interact with each other

JSON: {“name”} XML: <name> </name>

Advantages: Easier for humans to read More compact Can be directly manipulated by JavaScript Disadvantages: Limited data types