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System Analysis and Design

National Institute of Technology Rourkela

Year 2012 Question Paper Solution


Question 1a: A Supermarket has policy for cashing customer’s cheques as per the given rule. If the cheque is a personal cheque, for $75, or less the cheque can be cashed. If the cheque is a customer’s pay cheque, it can be cashed over $75, provided it is a company accredited by the supermarket. Find out various conditions and values for each condition. Decide corresponding actions and draw a decision table for the above logic.

Ans 1a:

Type of Cheques – Personal (P) and Customers (C)

Amount of Cheques – Greater than $ 75 (>75), Less than $ 75(<=75)

Type of Customers – Supermarket Accelerated (SA), Others (OO)

 

P

C(SA)

C(OO)

P

C(SA)

C(OO)

Amount

>75$

>75$

>75$

<=75$

<=75$

<=75$

Cashed

 

X

 

X

X

X

X- Denote Cheques is Cashed.

Question 1b: Differentiate between forms and reports.

Ans 1b: Forms:  Forms are used for taking input for producing a report.

Report:  Reports are usually written in user’s language, (not necessarily non-technical language). Reports are generated after conducting a survey using web form or any other means. Normally report contains Objective of the System or evaluation of any component of system.

Question 2a: A publishing company produces scientific books on various subjects. The books are written by author who specializes in one particular subject. The Company employs editors who, not necessarily being specialists in a particular area, each take sole responsibility for editing one or more publications. A publication covers essentially one of the specialist subjects and is normally written by a single author. When writing a particular book, each author works with one editor but may submit another work for publication to be supervised by other editors. To improve their competitiveness, the company tries to employee a variety of authors, more than one author being a specialist in a particular subject. Draw ER diagram for the above condition.

Ans 2a:

Question 2b: What’s wrong with each of these definitions?

CUSTOMER_REC=CUSTOMER_NAME + {ORDER_NO + ORDER_DATE}

STUDENT=STUDENT_NUM + STUDENT_NAME + 20{SUBJJECT}

Ans 2b:

Question 3a: Distinguish between logical design and physical design.

Ans 3a: Logical Design: The objective of this phase is the development of a design which is directed by an abstract machine and operating environment. This model contains the highest amount of quality and quality components as we were able to incorporate, with the time and talent available. We don’t consider those aspect in logical for which we can’t be sure until and unless we start implementing it.

Physical Design: The objective of this phase is the creation of a blueprint of the system. This blueprint is complete and correct and accurately describes every aspect of the system to be developed.

 

The activities which occur during the Logical design phase are the following:

  • Develop the preliminary design: the goal of this task is to create a conceptual design which will reflect in the analysis package and contain the amount of quality that we can incorporate into it
  • Define the man-machine and machine-machine boundaries on DFD: Using the level -‘0’dataflow diagram developed during the logical modelling phase of analysis, identify which processes or functions will be allocated to hardware, software and manual procedures.
  • Transform E-R-A Model into Relational Model: Each entity and each relation is transformed into a logical relationship using the Relational Database Model notation and semantics. The relations are integrated into global relational schema. An E-R-A Model is a conceptual representation of real world, enterprise objects. It is composed of entities (with their attributes) and relationships between them.
  • Normalize Relational Model: the logical relational schema is transformed into a normalized schema to provide for logical data access and update integrity.
  • Prepare Database access Model: For each user view a logical data access specification is created, which defines the process followed in accessing the required data and the logical relations involved.
  • Verify against Normalized Relational Model: Inability to support required data access will cause the E-R-A Model and the logical relational Model to be refined appropriately.
  • Transform levelled DFDs into first-cut structure chart
  • Refine structure Chart using coupling, cohesion and adding additional functions, as necessary.
  • Develop pseudocode: the pseudocode for each module describes what the module does. The basis for most pseudocode is the structured English that was created during the analysis phase.
  • Revise Event Model: Refinement of this model is necessary in order to put it into a more acceptable form to accommodate the design and implementation perspectives.
  • Revise Relational Model: Bring this view of the system into compliance with the other revisions and refinements that have taken place.
  • Update Lifecycle Dictionary: One of the outcomes of transforming the analysis results into an initial design model is that new data elements have to be incorporated. Since Lifecycle Dictionary is the repository for information, it must be updated to reflect new parts of systems, descriptions of each of the modules.
  • Perform consistency check among Structure Charts, pseudocode, Event Model, E-R diagrams, Relational Model. Ensure that all parts of the design are accurate and mutually supportive.

 

Physical Design Phase: has a task as followings

  • Develop Detailed Design: It is derived from the logical Design by incorporating considerations of system size, timing constraint, the existence of hardware or software utilities, language features and other implementation considerations.
  • Review Preliminary Design Package: The purpose of this task is twofold. One is to identify and correct errors and necessary refinements. The other is to ensure that all that is necessary to accomplish the physicalization of the design is present and of sufficient quality to support this next phase.
  • Develop final (‘build to’) Structure Chart
  • Update Lifecycle Dictionary to reflect physical characteristics: The lifecycle Dictionary must include the compromises between the desired ( Detail Design) system and the obtainable ( Physical Design) one. The primary inputs or changes at this stage are: the ‘build to’ Structure chart process, dataflow and data access specifications; the implementation constrains from the packaging criteria; the changes to the Event Model; and the new DBMS data model and its operational characteristics.
  • Revise pseudocode: update the content of the pseudocode, as necessary, in order to accommodate the changes made to the system design during the packaging process.
  • Perform coupling and cohesion analysis
  • Revise Event Model
  • Reconcile all elements of module design package
  • Map to DBMS Data Model: The logical, normalized schema is translated into an initial DBMS schema. This schema is then refined to take advantage of the unique capabilities of the DBMS being used. The translation process is specific to the particular DBMS Data Model. Each translation starts with a logical relation and converts it into an appropriate DBMS structure.
  • Optimize DBMS schema access costs: Cost models are to determine optimal access paths to support the user data view requirements. Any modifications to the DBMS schema are verified against the logical relational schema.
  • Revise implementation estimates: This supports the concepts of iterative estimation refinement that is used in most engineering fields.

 

Question 3b: What are the usage of join and fork operation in DFD?

Ans 3b: Fork: A fork in a data flow means that exactly the same data go from a common location to two or more different processes, data stores, or sources/sinks (it usually indicates different copies of the same data going to different locations).

Join: A join in a data flow means that exactly the same data come from any of two or more different processes, data stores, or sources/sinks to a common location.

Question 3c: Define the terms: process modelling, logic modelling, conceptual data modelling.

Ans 3c: Process Modelling:  Process modelling involves graphically representing the processes, or actions, that capture, manipulate, store, and distribute data between a system and its environment and among components within a system. A common form of a process model is a data-flow diagram (DFD). A data-flow diagram is a graphic that illustrates the movement of data between external entities and the processes and data stores within a system.

Logic Modelling:  Although data-flow diagrams are good for identifying processes, they do not show the logic inside the processes. Therefore we need Logic Modelling to represent logic inside a process.  Type of Logic Modelling are Decision Tables (Decision tables allow you to represent in a tabular format a set of conditions and the actions that follow from them),  Decision Tree (This is a graphical representation of decision in which nodes[Represented by circle and denotes decision points)  are connected together arrow and terminates on Ovals[Resultant Activity])

Question 4a: Distinguish between technical operational and economic feasibility with suitable Example.

Ans 4b: Technical Feasibility: This is concerned with specifying equipment and software that will successfully support the tasks required. The technical needs systems will vary considerably, but might include:

  • The Facility to produce outputs in a given time scale. For Example. 20,000 examination certificates in three weeks.
  • The ability to provide certain response times under certain consideration For Example , no more than a two second response time at each terminal when there are four terminal being used simultaneously.
  • The facility, to input a large number of documents, in a limited time scale. For example, 40,000 gas readings in one day.
  • The ability to process a certain volume of transactions at a certain speed. For examples, to report on seat availability and record airline reservations without a significant delay to the passenger.
  • The facility to communicate data to distant locations, for example, Regional sales figures transmitted to an American head Office.

Operational Feasibility:  Operational Feasibility is concerned with human, organisational and political aspects. General impressions of these factors may be gained from the corporate appraisal and through consideration of the system trigger. Amongst the issues examines are:

  • What job changes will the system bring? Most people react unfavourably to change. Planned job changes must be carefully handled so that those affected are seen to gain in a way that they feel is acceptable. This may be through job enrichment or simply through raising wages.
  • What organisational structures are disturbed? The suggested system may cut across accepted organisational relationship and threaten the status of individuals and promotional expectations.
  • What new skills will be required? Do the current employees possess these skills? If not, can they learn them? How long will they take to learn?

Economic Feasibility: Many organisations evaluate projects on an economic basis- they show financial returns that outweigh the costs. For this reason, management tend to give more weight to economic feasibility than to technical and operational considerations. A number of approaches to assessing the cost of solutions have been suggested. Approaches include the following.

Least Cost: This is based on the principle that costs are easier to control and identify than revenues. Thus it assumes that there is no income change caused by the implementations of a new system or that two competing system offer the same benefits. In such an evaluation only the costs are listed and the option with the lowest cost is selected.

Time to payback: The time to Payback method of economic evaluation is an attempt to answer the question “How long will it be until we get our money back on this investment in systems?” This requires data on both costs and benefits. The net cash flow for each year is calculated by subtracting the value of benefits. In the ‘Time to PayBack’ method, the alternative which repays the initial investment the quickest is selected.

Net Present Value: This is the well-defined and practised method of economic evaluations. It builds is an allowance for the ‘time’ value of money, represented by the Present Value Factor. In this method the net cash flows are reduced in value by applying this factor, so reducing the value of a cash flow to its present worth. For example, a cash flow of $30,000 planned for ten years’ time will actually only be worth $4,800 if a present value factor of 20percent is used.

Breakeven Analysis: This technique id particularly useful when the system is subject to varying workloads. It distinguishes between fixed and variable cost and fixed and variable benefits. Breakeven points tell us when will we system will come in state of profit.

Question 4b: Explain the various drawbacks of SDLC (System Development Life Cycle) method

Ans 4b: Drawback of SDLC (System Development Life Cycle)

  • It is not easy to go back to earlier phase if any changes required.
  • Project rate is high, more emphasis on coding than on design analysis which result in failure of project.
  • Requirement specification in not clear.
  • Lack of cast tool
  • Manual Documentation and Code generation.

 

Question 5a: Discuss various methods of interaction of users with an information system.

Ans 5a:

Question 5b: Differentiate between top-down design and bottom-up design.

Ans 5b:

Question 6a: How DSS is different from MIS?

Ans 6a: Management Information System: A management information system (MIS) is a computer-based system that takes the raw data available through a TPS and converts them into a meaningful aggregated form. For Example, whereas a transaction processing system keeps track of sales, a management information system can pinpoint which item are selling slowly and which selling quickly. The MIS system can therefore direct the manufacturing department on what to produce and when. Developing a MIS calls for a good understanding of what kind of information is required, because managers themselves may not know precisely what they need or how they will use information. Thus, the analyst must also develop a good understanding of the business and the transaction processing systems that provide data for an MIS.

Decision Support Systems: A decision support system (DSS) is designed to help decision makers with decisions. Whereas an MIS produces a report, a DSS provides an interactive environment in which decision makers can quickly manipulate data and models of business operations. A DSS has three parts. The first part is composed of a database (which may be extracted from a TPS or MIS). The second part consists of mathematical of graphical models of business processes. The third part is made up of a user interface (or dialogue module) that provides a way for the decision maker to communicate with the DSS. A DSS may use both historical data as well as judgments ( or “What if” analysis) about alternative histories or possible furthers. As executive information system (EIS) is a DSS aggregation and selectively drill down into specific area where more detailed information is required A DSS is characterized nu less structured and predictable use. DSS software supports certain decision-making activities ( from problem finding to choosing a course of action). The system analysis and design for a DSS often concentrated on the three main DSS components, database, model base, and user dialogue. As with an MIS, a data orientation most often used for understanding user requirements. The systems analysis and design project will carefully document the mathematical rule that defines interrelations among different data.

Question 6b: A Company gives discount to its customers based on the type of customer and order. For the individual, only if order size is 12 or more, the manufacturer gives a discount of 50% and for less than 12 products, the discount is 30%. Whereas in case of shopkeeper or retailers, the discount policy is different. If the order is less than 12 then there is 15% discount. For 13 to 48 products order, the discount is 30%, for 49 to 84 products the discount is 40% and for more than 85 products the discount is 50%. Draw decision tree.

Ans 6b:

 

OTHER IMPORTANT QUESTION

What is a System?

A System is a set of interrelated set of business procedure(Components) used within a business unit, working together for purpose. A System has nine characteristics

  • Components: Component is irreducible part or an aggregate of parts, also called as Subsystem.
  • Interrelated Components: They are also the component but these components depend on other components for the completion of their work.
  • Boundaries:  A system has a boundary, within which all of its components are contained and which establishes the limits of a system, separating it from other systems. Components within the boundary can be changed, whereas systems outside the boundary cannot be changed.
  • Purpose: All the components works together to achieve an overall purpose for a system. The purpose of the system’s reason for existing.
  • Environment: Everything outside the system that influence the system. A system interacts with environment with receiving data and information.
  • Interface:  The point at which the system meets its environment is known as interface.
  • Constrain: Constrains are the limits (in terms of capacity, speed, or capabilities) to what it can do and how it can achieve its purpose within its environment. Some of these constraints are imposed inside the system (e.g., a limited number of staff available), and others are imposed by the environment (e.g., due dates or regulations).
  • Input: A System take input from environment through environment in order to function.
  • Output: Result generated by the system.

What is an Information System?

Information System is the arrangement of the people, data, process that interacts with each other to support and improve day to day activity of an organization with problem solving and decision making of the management. Major Objective of information system is to turn Data into information.

Information System consists of

  • Hardware and system software on which the application software runs.
  • Documentation and training material for helping employees to use software.
  • The Specific Job Roles associated with the software. Such as the people who runs the computer and keep the software operating.

Type of Information System:

  • Transaction Processing System(TPS)
  • Management Information System(MIS)
  • Decision Support System (DSS)
  • Expert System ( ES)

 

What is Difference between Data and Information?

Data: Raw which may represents quality quantity, Action or an Object.

Information: Information is the processed data.  Types of Information are

  • Strategic Information: For long term development and planning of organization. It is not structured.
  • Tactical Information: For short range decision making in an organization. More Structured than Strategic Information and more volume than strategic information.
  • Operational Information: Day to Day activity of System perfectly structured.

What is a Transaction Processing System?

Transaction Processing System: Automates that handling of data about business activities or transactions. For Example, a banks’ TPS would capture information about withdrawals from the deposits to customers’ accounts. Data about each transaction are captures, transactions are verified and accepted or rejected, and validated transaction is stored. Reports may be produced immediately to provide summaries of transactions and transactions maybe are, over from process to process in order to handle all aspects of the business activity. The goal of TPS development is to improve transaction processing by speeding it up, using fewer people, improving efficiency and accuracy, integrating it with other organizational information systems, or providing information not previously available.




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