• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Why analyse data?

Extracts from this document...

Introduction

Data Analysis Why analyse data? A basic form of database is a flat file of data. The file is made up of a series of records and each record has a series of fields in it. Top of File First Record Last Record Bottom of file Records may be fixed length (padded with spaces) or variable length (e.g. comma delimited). As we move to more complex applications, the type of data we work with expands. Eventually the flat file or single table becomes unsuitable. There may be many users that need to get access to the data for view or edit. Having more that one user updating the file at once causes problems. Different areas of the program may require access to different parts of the data. If the data is organised, smaller amounts need to be open for update. This improves accessibility and therefore performance. Speed of access reduces with increasing record count and record length. Often there are a number of similar items on a record e.g. exam results against a pupil on a student record (how many subjects, how many papers, how many slots do you need?). Organising you data in to different files or tables allows greater flexibility. Organising your data can be a difficult process, particularly with large systems with hundreds of tables. There are methods of analysis, which help us to avoid these problems. ...read more.

Middle

Attributes are the data types that are specific to the entity. In the library example, the entity CUSTOMER has ATTRIBUTES of ID, Name, address, contact number, limit and status. Attributes have DOMAINS. The domain of the attribute (field) is the set of values that are contained in the attribute across all the records. Looking at the entity 'Customer' in the library example, the attribute 'Name' would have a domain containing the names of all the customers and Status would have a domain of containing the different states of a customer account e.g. blocked, closed, normal The Entities also have RELATIONSHIPS with each other. The relationship between the keys of two entities operates in both directions. The relationship between Customer and loans would be described as 'A Customer may have one or more Loans' and 'A Loan must belong to one customer'. The relationship contains information telling us if a record in one table can exist with out a partner record in another table. Here, a loan can not exist with out a customer but clearly a customer may exist who never uses the library and never has a loan. In relational databases such as Oracle, Ingress and Access, these relationships can be enforced so that you can not enter a loan record for a customer that does not appear in the customer database. Below is one representation of this relationship. It can also be represented using 'crows feet' for Many and a single straight line as One. ...read more.

Conclusion

Entity Attribute Loan Loan ID ISBN Code Borrower ID Borrower name Date out Date due back Fine Due Times Renewed If Borrower name did not already exist in Customer, we would need to create a new entity for it. Since it does already exit, its appearance in this entity was purely data redundancy so it can be removed entirely. Entity Attribute Loan Loan ID ISBN Code Borrower ID Date out Date due back Fine Due Times Renewed This is now in 3rd Normal Form. We can see that by normalising the data we have generated extra entities, which will in turn have relationships. The process is iterative and for major systems, teams of analysts have 'walk through' sessions to ensure accuracy of the data structure. Normalisation becomes almost second nature after a while. The problems are often dealt with in the E-R Modelling stage with out realising it because much of it is common sense. It is still a useful tool to double check that you have not missed anything. Final Structure Entity Attribute Customer Borrower ID Name Address Contact Number Account Status Customer Media Details Media Type Borrower ID Media Limit Media Status Media Media Type Media Description Loan Loan ID ISBN Code Borrower ID Borrower name Date out Date due back Fine Due Times Renewed Book ISBN Code Title Author Publisher Loan Period NB This data model does not cater for multiple copies of a book. Also, the other media types may not have ISBN numbers. Systems Analysis 13/11/00 Page 1 of 8 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Computer Science section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Computer Science essays

  1. Programming Techniques

    The tester can only design the tests for white box testing once the code has been written. Black box Testing It is so described because the code is viewed as being inside a black box, or unreadable. Tests that are carried out are based upon feeding data into the box and observing what comes out.

  2. Ict Analysis

    6. What experience of using a computer do you have? - I personally have had a lot experience of using a computer as we have one in the restaurant. However it's not used to store information. It is mostly used for sending emails.

  1. Program Code Program DVD_Program; Uses Menuunit, CRT, dos; ...

    Write ('Number of copies:'); Write (two_rec.stock_number); End; {--------------------------------------------------------------------} {This procedure is used to locate a member record stored in the database.} Procedure locate_member_record; VAR mid: longint; Begin found:= false; Clear_Selected; Save_Screen; Draw_Shadow_Box (10, 9, 70, 20); TextColor (15); Gotoxy (12, 10); Write ( 'Locate member record...'); Gotoxy (12, 11); TextColor

  2. importance of data security and data safety

    * What is a browser? Is programme that can read web pages, by downloading HTML code and that allows the browser to interpret the code to the web page. A browser displays web pages, keeps track of where you've been, and remembers the places you want to return to, the most used browsers are Internet Explorer and Netscape Navigator.

  1. Flexible Architectures in Communication Security Application

    Specifically, I contributed the following: i) design and implementation of the CryptoManiac functional units, ii) area, timing, power, and Lisa Wu Page 12 4/22/01 performance analyses of the CryptoManiac, iii) experiments for design parameter decisions such as the bypass logic of the CryptoManiac, the width of the VLIW co-processor, and

  2. CP3 - Proposed Solution to a Realistic Problem - Apartment Administration software

    POSSIBLE LIMITATIONS * The computer the program is installed on may not have a high enough specification. Will money have to be spent upgrading the computer? * Users may not know to use the system. The system relies on basic computer knowledge of the user however there could be exceptions

  1. Spare Parts Database Project

    Wong; If an account is lost and cannot be retraced, I am obliged to close the account, whereas for an important document I have to write to the person to send me another. 12. Self: How much salary does an employee get?

  2. ELECTRONIC DATA INTERCHANGE

    Can you do EDI on your current system? If not, you will need to decide which hardware platform best suits the needs of your business. Software choice will center on whether to develop in-house or purchase third party coding. A decision will need to be made whether to build EDI

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work