Contents -
  • Introduction of Information Technology Infrastructure and Information System Architecture (ISA).
  • Components of Information System.
  • Information System Architecture Model.
  • Services in Information System Architecture.
  • Classification of Information System Architecture.


What is Information Technology Infrastructure ?


An information technology infrastructure contains hardware components, software components and services provided by staff member of the organization integrated together.
An information technology infrastructure can be broadly divided into 5 parts :
  1. Hardware Components
  2. Software Components
  3. People
  4. Database and Storage Devices
  5. Networks and Communication Components
It also included suitable operational integration of above components with their documentation, maintenance and management.

What is Information System Architecture (ISA) ?


Information System Architecture (ISA) refers to the business processes and policies, system structure, technical structure and product technologies required for a business or an information system.
The architecture comprises a detailed description of design, contents, list of current hardware, software and networking capabilities of the computerized system. This architecture include both the hardware and software used to provide solution to the customer. It also include details of long-term plans like upgrading and/or replacing old equipment and software.
The information system architecture of any firm can be considered as a blueprint depicting how the data processing system, telecommunications networks and data are incorporated. It provide a summarized response to the following questions :
  • Where to store data ?
  • What data is gathered ?
  • How and were the data gathered ?
  • Which application use the data and how are they related to overall system ?
  • How is the data transferred ?

Components of Information Systems


There are five main resources of information system. These resources are explained as follows :

1. Hardware Resources :

Hardware resources refer to all physical devices that are used in processing of information. It not only include computers and other equipment but also any tangible object of which data can be stored which range from a simple sheet of paper to magnetic or optical disks. Few hardware resources are as follows :

A) Computer Peripherals :
These devices are used in computer to, input the data, store data and provide the output.
For example : keyboard is used for data input, printer for output information and magnetic tapes for storing information.

B) Computer Systems :
This comprises of a central processing unit containing microprocessors and numerous interconnected peripheral devices.
For example : handheld devices, laptop or desktop micro computer systems, mid-range and large mainframe computer systems.

2. People Resources :

People play a crucial role for effective operation of all the information system. The different type of people resources are as follows :

A) IS Specialists :
Those people who develop and operate information system are known as IS specialists. They may be system analysts, software developers, system operators and other managerial, technical or clerical IS personnel.

B) End Users (Users or Clients) :
Those user who use an information system or the information which produced by it, are known as end users.
For example : customer, sales person, engineers, Clark, Accountants or managers. Almost all the people are end users.

3. Data Resources :

It is a valuable organisational resources, it must be managed effectively to benefit all end users in an organisation. The concept of data resources has been widened by managers and information system professionals to include much more than raw material of information system. Data are resources are organised, stored and accessed by data resource management technologies in the form of :
A) Knowledge base that comprise knowledge in various forms such as facts, rules and case example of successful business practices.
B) Database that contain processed and organised data.
For example : Sales transaction data is gathered, processed and stored in a web enabled sales database which is used for sales analysis reports by managers or marketing professionals. Knowledge base is used by knowledge management system and expert systems for sharing knowledge for giving expert advice on particular domain.

4. Software Resources ;

The collection of instruction is known as software. The instructions which are used to direct and control the computer hardware are known as programs and The instruction which are used to process data are known as procedures. Software are of two types, they are as follows :

A)  Application Software :
This software for direct and support the particular task of computers are required by end users. e.g. MS Word, MS Excel, library management system etc.

B) System Software :
The software control and direct the operations of computer system. e.g. Operating System.

5. Network Resources :

E-business and e-commerce operations of all types of organisation and their information system will succeed if telecommunication technologies and network like internet, intranet and extranet are in place. Telecommunication network comprises computer, communication processes and other devices interconnected by communication media and controlled by it software. The fundamental resources components of all information system are communication technologies and network. The main network resources are as follows.

A) Network Infrastructure :
It refers to the hardware, software and data technologies used to support and control the organisations of communication network. e.g. Modems, inter-network processors and communication control software (network operating system and internet browser packages).

B) Communications Media :
These are used to deliver and receive information or data.
For example : Twisted pair wire, coaxial and fibre optic cable, microwave, cellular and satellite wireless technologies are used for this purpose.

Information System Architecture (ISA) Model


Information System Architecture has the following basic building blocks :

1) IS Block :
The IS block provide the functions which support business process. IS blocks are related to other blocks via IS services and are executed in IT blocks.

2) Information Entity :
Various business processes are responsible for the creation, reading, updating or deleting of information entity data. IS block use the information entity and it physically exists in an IT blocks.
For example : Data pertaining to an information entity exists in association with other entities.

3) IT Blocks :
IT blocks helps in implementing IS block and manipulation of information entity data.

Services in Information System Architecture (ISA)


Service refers to a collection of a group of operations offered by an architecture block. It comprises of web service and business and system services offered by various blocks. ISA  comprises of three different services :

1) IT Service :
This includes the technological services offered by application platforms.

2) Business Service :
This is a set of operations offered by IS blocks which support one or more business process.

3) IS Service :
This refers to the collection of operation offered by an IS block to other IS blocks.
Operation is something which can be defined as the description of an action maintained by service. Therefore, operations provide minor detail related to ISA.

Classification of Information System Architecture (ISA)


The following is the classification of the information system architecture :

1) Client- Server Architecture :
The client server model of computing separate tasks between resource or service providers referred to as servers and service requesters refers to as clients.
Client/server architecture is a general model in any software organisation which can be executed in several ways.
For example : The interaction between client application program being executed on a workstation and a database management system (DBMS) executing on a larger computer system.

Database access request are sent by the application program to the database management system through a network. The DBMS will access the data on behalf of the application and will provide a response in the form of result of search operation for success/failure report of an update operation.

The client/server software architecture is a flexible, message based and modular infrastructure. It aims to improve the usability, interoperability, flexibility and scalability as opposed to the centralized, mainframe, time sharing computing.
The components of this architecture are the client, the requesting machine and the server, this supplying machine. These are connected to each other by either a local area network (LAN) or wide area network (WAN).

The server performs the following functions :
  • Processing of the query.
  • Return the result to the client.
  • Note the client query.

The client has the following responsibility :
  • Decode the user's request into specific protocols to enable processing.
  • Tackle the user interface.
  • Presenting the result to the user.
  • Wait for the server to respond.
  • Sending the request to server.
  • Convert the response into readable format.

2) Mainframe Architecture :
In Mainframe, The Terminal accept query from users but does not validate it. This is done by the server along the processing of the request. This type of architecture was prevalent till the mid-1998's with the scenario being completely different now. Such architecture is not used now for its inflexibility and bad cost to performance ratio.
As an extension of this paradigm, comes the smart terminal concept. Here, a mainframe is combined with a number of PC's as smart terminals, each of which contain a keyboard and screen as well as a disk drive which perform limited processing tasks. This reduced the dependency of always communicating with the central computer. Mainframe architecture comprises of :
A) A terminal users input queries to which the results are displayed.
B) A server which processes data within the network.
The user submits to request for data via a terminal. The server will the process the request and the result will be displayed on the terminal screen.

3) Distributed System :
A distributed system comprises of a collection of independent computer which are connected by network and distributed operation system software. This enables the computers to co-ordinate their activities and share the system resources. This gives a feeling to the user that it is a single. Integrated computing facility.

Characteristics of Distributed System -
The following are the characteristics of the distributed system :

i) Openness :
The openness of DS is dependent on the quality of new resource sharing services which can be added and made available to client programs.

ii) Resource Sharing :
  • Distributed system also makes information exchange easier among users.
  • In distributed system, it becomes easy for user to access remote resources which can also be shared among users. For example, printers, files, web pages etc.
  • As resource and data sharing is easy, it may cause security problems which have to be dealt efficiently.

iii) Concurrency :
Many clients may attempt to access the same resource simultaneously. Therefore, the operations of a shared resource must always be correct in a concurrent environment for optimum performance.

iv) Transparency :
Processes and resources are distributed physically among multiple computers. This fact remains hidden in DS. The different forms of transparency are as follows :

Transparency

Description

Access

The differences in data representation and the way to access a resource are hidden.

Location

Hide the location of the resource.

Migration

Hide that a resource may be moved to another location.

Relocation

Hide that a resource may be moved to another location while still in use.

Replication

Hide that a resource is being replicated.

Concurrency

Hide that a resource may be shared by several competitive users.

Failure

Hide that failure and recovery of resources.

v) Scalability :
A system is said to be scalable when it remains efficient despite increase in resources and users.
Challenges : Controlling loss from poor performance and Controlling the resources cost or money.

4) Web Based Architecture :
Database architecture can be said to be an extension of the client/server architecture but there are certain differences. The application software is present in the client workstation in client/server architecture which is used to communicate with the application server. However, in the web based application the client machines have web browsers which are network to web browser by LAN or WAN.

Initially, there was very little interactivity on the web. The user would send a query via forms or URL so as to receive a response from the server. The server then returned the search result in HTML format where the browser was responsible for providing the HTML code. It was the introduction of AJAX which had a major impact on the web application as it made allowance for change in small part of the page without the need to reload it. This also allowed the change to go back to the main server for fetching additional information 
It comprises of many web application that are present on internet. They get implemented on the web browsers or as an individual Java application.

In web-based architecture, the server does not return HTML for every request. Instead, it returns a page that contains the UI logic which goes back to the main server through web services and fetches the required information. Thus, what the server returns in a UI application which can be implemented by the browser.

There are several AJAX calls in web architecture. When the web structure is considered as at something organised and structured, having authentication standard request/response formats, etc. then the difference arises. AJAX calls in traditional application refresh certain parts of UI which respond specifically to the UI problem at hand. Web Services using standard data format which can be used in different context apart from the particular web application. It may be used by another web application, batch process or desktop application.

In above figure depicts that the page gets loaded without data. It contain the HTML and JavaScript which control the UI. Once the page is provided and JavaScript executed, the code calls the web services to acquire information which is placed in the UI using JavaScript. Later, once the user interacts with the application and information is to be fetched from the server, a call to the web services delivers the response which is processed to alter UI.

Web based application refers to those application which are present on a resident server and can be accessed by anyone in the world through a web browsers. This is the only client side software required. The application must also confirm to the internet protocol for it to be accessed from anywhere in the world through a web browser. An online store would be an example of such an application. Two other features of web based functionalities are as follows :
1. Web-based system are accessible globally via browser depending on user access rights.
2. The content/data generated is updated in real time.
Internet, intranet and extranet are the principal communication network of the web environment.

5) Cloud Architecture :
The cloud computing architecture of a cloud solution refers to the structure of the system which includes on premise and cloud resources, services, middle ware and software components with their geo-location, externally visible properties and their inter-relationships.

In cloud computing, the right protection is dependent on the correct architecture for the corresponding application. Thus, organisations must understand the requirement of each application to ensure optimum performance and if already using Cloud Computing, then they must understand the matching cloud architecture.

Multiple cloud components are a hallmark of cloud architecture which communicate with each other over loose coupling mechanism like a messaging queue. Elastic provisioning refers to the uses of tight or loose coupling of cloud resources, services, middle ware and software components.

Cloud computing architecture comprises of a front and a back end which the inter connected by network like internet. The front end is viewed by the client or the user and the back end is the cloud section. 

A) Front End :
The client devices like computer network and application required for access of cloud computing system comprises the front end. All system do not provide the same interface to users.
Electronic mail programs use existing web browsers like Firefox, Microsoft Internet Explorer or Apple Safari. Some other type of system might have exclusive application which helps in network access to clients.

B) Back End :
The physical peripherals comprise the back and which may include computer machines, data storage system and servers. In theory, a cloud computing system includes web application programs like video game, data processing, software development and entertainment. A complete cloud computing system is made up of a group of Clouds. 
Each application has its own server with one central server used for controlling the entire system like monitoring clients demand. It is the middle-ware which allows communication between computers on the same network. In case a cloud computing service provider has a huge customer base then it would require use storage space for which storage devices are required. Also the cloud computing system has a copy of all data of its clients which is referred to as redundancy. This centre server uses a specific type of software called middle ware and follow certain protocols.

6) Grid Architecture :
Grid architecture refers to sharing of resources in a distributed environment in a particular design of a grid. The resource layer lies just about this which comprises computers, storage system, electronic data catalogues, sensors and telescopes connected to the network. It has various layers where each layer has a particular function which higher layers being user-centric and lower layers being hardware centric. Network is the lowest layer which connects the grid resources.

The middle-ware layer supplies the tools which facilitate participation of the different elements in a grid like servers, storage, networks etc. Thus, it is also referred to as the brains of a computing grid.

The application layer is the highest layer of a grid comprising application in Science, Engineering, Business, Finance etc. and also portals and development tool-kits to support applications. It may also include service-ware that perform general management functions such at tacking grid resources provisioning and uses. It is also the layer that the grid users see and use.

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