Chapter 3 E-commerce Architecture Chapter - 3 E-commerce Architecture 26 Chapter 3 E-commerce Architecture 3.1. E-commerce Architecture: Every day more and more business transactions are conducted in the Internet under the umbrella of ECommerce. The main feature that distinguishes E-Commerce from traditional commerce is the ability to conduct business with spatially distributed partners and products, and achieves considerable reduction in human effort and latency time. The size and complexity of E-Commerce systems make the architecture level of design and specification of the overall system a significant issue. From a good design it is possible to assess the quality and performance of the system before the system is implemented and deployed. Some of the important properties that can be assessed from a design specification include correctness, service availability, and security of transactions. This paper discusses the model of E-Commerce architecture towards this goal. There are four types of E-commerce Architecture 1. Client Server Architecture 2. Two-Tier Architectures 3. Three-Tier Architectures 4. Distributed Enterprise Architecture 3.2. Client–server architecture: The client–server architecture is a computing model that acts as a distributed application which partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. [Fig: Client Server architecture] 27 Chapter 3 E-commerce Architecture Often clients and servers communicate over a computer network on separate hardware, but both client and server may reside in the same system. A server machine is a host that is running one or more server programs which share their resources with clients. A client does not share any of its resources, but requests a server's content or service function. Clients therefore initiate communication sessions with servers which await incoming requests. A network architecture in which each computer or process on the network is either a client or a server. Client Server architecture use 3 components- 1. Clients (Clients are Applications): Applications that run on computers and Rely on servers for Files, Devices, Processing power. Make requests, Format data on the desktop. Example: E-mail client an application that enables you to send and receive e-mail. 2. Servers (Servers Manage Resources): Computers or processes that manage network resources, Disk drives (file servers), Printers (print servers), Network traffic (network servers).Store and protect data, Process requests from clients. Example: Database Server -A computer system that processes database queries. 3. Communication Networks: Networks Connect Clients and Servers. 3.2.1. Client/Server architecture Propertis: E-commerce is based on client/ server architecture 1. Client processes requesting service from server processes 2. First used in 1980s, the model improves to be e-commerce usability, flexibility, interoperability and scalability. • In e-commerce the client is defined as the requestor of a service and a server is the provider of the service 3. Browser is the client and the customer, the computer that sends the HTML files is the server 4. The server can also be a computer program that provides services to other computer programs • A web server is the computer program that serves requested HTML pages or files. 5. Uses client/server model and http(hypertext transfer protocol) 28 Chapter 3 E-commerce Architecture 6. Every computer on the internet that contains a web site must have a web server program. • Most popular web servers are Deerfield’s WebSite and Microsoft’s Internet Information Server (IIS) • Web servers are included as part of a larger package of internet and intranet related programs for serving e-mail, downloading requests for FTP files and building and publishing web pages. • Typically the e-commerce customer is the client and the business is the server. • In the client/ server model single machine can be both client and the server • The client/ server model utilises a database server in which RDBMS user queries can be answered directly by the server • The client/ server architecture reduces network traffic by providing a query response to the user rather than transferring total files. • The client/ server model improves multi-user updating through a graphical user interface (GUI) front end to the shared database. • In client/ server architectures client and server typically communicate through statements made in structured query language (SQL). 3.2.2. Clients-server interaction: The client–server characteristic describes the relationship of cooperating programs in an application. The server component provides a function or service to one or many clients, which initiate requests for such services. Functions such as email exchange, web access and database access, are built on the client–server model. Users accessing banking services from their computer use a web browser client to send a request to a web server at a bank. That program may in turn forward the request to its own database client program that sends a request to a database server at another bank computer to retrieve the account information. The balance is returned to the bank database client, which in turn serves it back to the web browser client displaying the results to the user. The client–server model has become one of the central ideas of network computing. Many 29 Chapter 3 E-commerce Architecture business applications being written today use the client–server model. So do the Internet's main application protocols, such as HTTP, SMTP, Telnet, and DNS.The interaction between client and server is often described using sequence diagrams. The Unified Modeling Language has support for sequence diagrams. Specific types of clients include web browsers, email clients, and online chat clients. Specific types of servers include web servers, FTP servers, application servers, database servers, name servers, mail servers, file servers, print servers, and terminal servers. Most web services are also types of servers. 3.2.3. Client/Server with File Servers In the client/server architecture, a file server is a computer responsible for the central storage and management of data files so that other computers on the same network can access the files. A file server allows users to share information over a network without having to physically transfer files by floppy diskette or some other external storage device. Any computer can be configured to be a host and act as a file server. [Fig: Centralized Client/Server with File Servers] 30 Chapter 3 E-commerce Architecture A file server may be an ordinary PC that handles requests for files and sends them over the network. In a more sophisticated network, a file server might be a dedicated network attached storage (NAS) device that also serves as a remote hard disk drive for other computers, allowing anyone on the network to store files on it as if to their own hard drive. [Fig: Distributed Client/Server with File Servers ] A program or mechanism that enables the required processes for file sharing can also be called a file server. On the Internet, such programs often use the File Transfer Protocol (FTP). 3.2.4. Client/Server with Database Servers: A database server is a computer program that provides database services to other computer programs or computers, as defined by the client–server model. The term may also refer to a computer dedicated to running such a program. Database management systems frequently provide database server functionality, and some DBMS s (e.g., MySQL) relies exclusively on the client–server model for database access. Such a server is accessed either through a "front end" running on the user’s computer which displays requested data or the "back end" which runs on the server and handles tasks such as data analysis and storage. In a master-slave model, database master servers are central and primary locations of data while database slave servers are synchronized backups of the 31 Chapter 3 E-commerce Architecture master acting as proxies. Events (violation of integrity constraints, temporal conditions, errors) trigger event handlers-> implicit invocation, blackboards, and event. [Fig: Client/Server with Database Servers] A DBMS also offers features for recovery and concurrency control Some examples of Database servers are Oracle, DB2, Informix, Ingres, SQL Server. Every server uses its own query logic and structure. The SQL query language is more or less the same in all the database servers. At present the majority of existing client/server-based software is to be found in the area of databases, and it is here that the greatest challenge to any corporation currently lies. Richard Finkelstein, President, Performance Computing 3.2.5. Client/Server with Transaction Processing : 32 Chapter 3 E-commerce Architecture Transaction processing is designed to maintain a computer system (typically a database or some modern file systems) in a known, consistent state, by ensuring that any operations carried out on the system that are interdependent are either all completed successfully or all canceled successfully. 1) Atomicity a) A transaction is an indivisible unit of work. b) An all-or-nothing proposition. c) All updates to a database, displays on the clients’ screens, message queues. d) e.g., salary increase for all 1 million employees or none 2) Consistency a) a transaction is an indivisible unit of work b) integrity constraints (e.g., mgr.salaray > salary c) Isolation [Fig: Client/Server with Transaction Processing ] d) A transaction’s behavior not affected by other transactions running concurrently. 33 Chapter 3 E-commerce Architecture e) E.g., reserve a seat. 3) Serialization techniques a) Durability b) Persistence c) A transaction’s effects are permanent after it commits 3.2.6. Advantages of Client Server Architecture: 1) Centralization: In Client Server Networks there is no central administration, here in this architecture there is a centralized control. Servers help in administering the whole set-up.