Enterprise Systems MIS 181.9: Service Oriented Architecture 2 nd Semester,

Learning Objectives ► At the end of this section, students should be able to: ► Identify the different components of enterprise automation. ► Review history of computers, focusing on the development of enterprise systems. ► Review the different architectures used for enterprise systems.

Scope of Enterprise Automation ► Application ► Automating business functions ► Application development technologies ► Infrastructure ► Hardware, network technologies ► System software ► Architecture ► Overall plan

Early Enterprise Systems: MAINFRAMES ► Powerful computers ► Able to process several transactions at a time ► CENTRALIZED COMPUTING

Mainframe An ICL 2966 Model 39, at the National Museum Of Computing, Bletchley Park, UK

Terminal

Mainframe System Components ► Hardware technologies ► Vacuum tubes, magnetic drums, magnetic tapes (1950s) ► Transistors (1960s) ► Large-scale integrated circuits (LSI) (1970s) ► Software technologies ► COBOL, FORTRAN programming languages ► MVS, z/OS (operating systems) ► CICS (transaction management), IMS (IBM Hierarchical DB), RACF (security)

Where were Mainframes used? ► Used in universities, airline companies, US government agencies ► Research ► Department of Defense ► Weather Bureau ► First computer used for business ► LEO Payroll

Major Players in the Mainframe Industry ► IBM ► Burroughs ► UNIVAC ► NCR (National Cash Register) ► Honeywell ► RCA (Radio Corporation of America) ► GE (General Electric)

Personal Enterprise Systems? ► Personal Computers were introduced in 1970s ► Smaller computers ► Enough power to perform simple applications ► Further development in network technologies

Client/Server System ► Leverages on development of powerful PCs and development of Network technologies ► DISTRIBUTED COMPUTING

Client/Server Systems ► Networked computing model ► Processes distributed between clients and servers ► Client–Workstation (usually a PC) that requests and uses a service ► Server–Computer (PC/mini/mainframe) that provides a service ► For DBMS, server is a database server

Application Logic in C/S Systems GUI Interface Procedures, functions, programs DBMS activities Processing Logic  I/O processing  Business rules  Data management Storage Logic  Data storage/retrieval Presentation Logic  Input–keyboard/mouse  Output–monitor/printer

Client/Server Architectures ► File Server Architecture ► Database Server Architecture ► Three-tier Architecture Client does extensive processing Client does little processing

File Server Architecture ► All processing is done at the PC that requested the data ► Entire files are transferred from the server to the client for processing ► Problems: ► Huge amount of data transfer on the network ► Each client must contain full DBMS ► Heavy resource demand on clients ► Client DBMSs must recognize shared locks, integrity checks, etc. FAT CLIENT

Figure 9-2 File Server Architecture FAT CLIENT

Two-Tier Database Server Architectures ► Client is responsible for ► I/O processing logic ► Some business rules logic ► Server performs all data storage and access processing  DBMS is only on server

Advantages of Two-Tier Approach ► Clients do not have to be as powerful ► Greatly reduces data traffic on the network ► Improved data integrity since it is all processed centrally ► Stored procedures  DBMS code that performs some business rules done on server

Advantages of Stored Procedures ► Compiled SQL statements ► Reduced network traffic ► Improved security ► Improved data integrity ► Thinner clients

Figure 9-3 Two-tier database server architecture Thinner clients DBMS only on server

Three-Tier Architectures Thin Client PC just for user interface and a little application processing. Limited or no data storage (sometimes no hard drive) GUI interface (I/O processing) Browser Business rules Web Server Data storage DBMS Client Application server Database server

Figure 9-4 Three-tier architecture Thinnest clients Business rules on separate server DBMS only on DB server

Advantages of Three-Tier Architectures ► Scalability ► Technological flexibility ► Long-term cost reduction ► Better match of systems to business needs ► Improved customer service ► Competitive advantage ► Reduced risk

Application Partitioning ► Placing portions of the application code in different locations (client vs. server) AFTER it is written ► Advantages ► Improved performance ► Improved interoperability ► Balanced workloads

Figure 9-5a Two-tier client- server environment Figure 9-5b n-tier client- server environment Processing logic could be at client, server, or both Processing logic will be at application server or Web server Common Logic Distributions

Middleware ► Software that allows an application to interoperate with other software ► No need for programmer/user to understand internal processing ► Accomplished via Application Program Interface (API) “glue” The “glue” that holds client/server applications together

Types of Middleware ► Remote Procedure Calls (RPC) ► client makes calls to procedures running on remote computers ► Message-Oriented Middleware (MOM) ► Software needed to run programs written in different platforms ► Publish/Subscribe ► push technology  server sends information to client when available ► Object Request Broker (ORB) ► object-oriented management of communications between clients and servers ► SQL-oriented Data Access ► middleware between applications and database servers

Database Middleware ► ODBC–Open Database Connectivity ► Most DB vendors support this ► OLE-DB ► Microsoft enhancement of ODBC ► JDBC–Java Database Connectivity ► Special Java classes that allow Java applications/applets to connect to databases

Approaches to Designing Client/Server Architectures ► Distributed Presentation ► Remote Presentation ► Remote Data Management ► Distributed Function ► Distributed Database ► Distributed Processing

Distributed Presentation Freshen up delivery of existing server-based applications, typically running on legacy mainframe computers, to distributed clients using screen scrapper technology

Remote Presentation All data presentation functions are on the client, providing greater flexibility of presentation than the distributed presentation option.

Remote Data Management All software except data management is on client, this is closest to the traditional client/server mode.

Distributed Function Analysis functions are split between client and server, with all presentation on client and all data management on server. Requires coordination between analysis function on client and server, making it difficult to develop and maintain.

Distributed Database Client has all functionality, except that data storage and management is shared between client and server. A distributed database is unstable, and it is very difficult to ensure compatibility and communication between client and server.

Distributed Processing Combines distributed function and distributed database, maximizing flexibility of analysis and data management

Web Systems ► Another form of distributed systems ► WAMP/XAMP provides one-time installation of a set of system software needed to develop web-based systems. Each software represents a tier in the distributed environment ► Apache (Web Server software – Web Server) ► MySQL (DBMS – DB Server) ► PHP (Programming Language – Application Server) ► Internet ► Web Technologies ► Businesses can use it internally (Intranet) or with clients (Extranet)

Figure 10-1 Database-enabled intranet/internet environment

Internet and Intranet Services ► Web server ► Database-enabled services ► Directory, security, authentication ► ► File Transfer Protocol (FTP) ► Firewalls and proxy servers ► News or discussion groups ► Document search ► Load balancing and caching

The Enterprise System using Web-based Architecture ► Intranets ► Extranets ► Software as a Service

Intranets as Information Portals

Extranet Connectivity

Emerging Web Technologies ► Software as a Service (SaaS) ► Used to be known as Application Service Providers (ASPs) ► Provider licenses customers to use their software as a service on demand ► Cloud Computing