Day 2 : Class Diagram

This is my class diagram of the POJO classes so far, for the primary school. I used 'STAR UML' tool for drawing and generating the java code.You can download the tool from sourceforge.net for windows. I got an error in the principal class when I was generating the code; need to work on that later.

Class Diagram : Primary School
 (you can zoom it for the detailed view.)

How to make a system in 25 days? ctd...

Utilizing the break...

I'm using java for coding.

Class Diagram

purpose: show the types being modeled within the system

Example of a class diagram for the class 'Flight' would look like this

Mapping a class diagram

• Packages - map to Java package names
• Classes - map directly to Java classes
• Interfaces - map to Java interfaces
• Attributes - map to Java properties and fields
• Associations, Aggregations, Compositions - map to Java references
• Operations - map to Java methods
• Generalizations - map to Java inheritance relations 
• Attributes - map to Java properties and fields  
• Attributes - map to Java properties and fields  
• Realizations - map to implementation of Java interfaces 
• Dependencies - at the most basic level these just map to Java import statements

UML Associations 

Cardinality - a cardinality of one on a given relationship end generates a Java reference

Aggregation
    Composition associations - child object can not exists with out the parent.when the parent is deleted child also is deleted when we implement in java.
    Aggregation Association - same behavior as a regular association.

One to many association



resulting code for this is something like following.

public class Customer {
  List getPurchases() {...}
  void setPurchases(List purchases) {...}
  ...
}

This link is a good reference on class diagrams
You might find this useful too

How to make a system in 25 days?

Day1 : Today's Ingredients


1.  A midsummer Night's Dream Felix Mendelson (Music) 
In case things get out of hand..


2 Creating Database & UML Diagrams




1....


2. Creating Database & UML Diagrams


First we need the database. 
You have to scratch your tables and then normalize.


Basics! 3 Normal forms. 
These are supposed to be just guidelines. Book says that It is sometimes necessary to stay away from these to implement requirements.


1st Normal Form


     No duplicate columns in one table.
     Create separate tables for related groups of data. IDentify each row with unique column/s-  Primary Key.

1NF: more>>

2nd Normal Form


    Remove duplicate data: 1NF should be applied already.
    If there is same data are used in multiple rows of a table, create separate tables for those duplicated and make a single table out of that.


After applying the 1st normal form lets say there is a table like this:
 Users table

• Address
• City
• State
• ZIP

After applying the first rule of 2NF rule there are two separate tables with following columns.
Users table 

• Name
• Address
• ZIP

zips table

• ZIP
• City
• State

To tie the two tables together we need a unique identifier for the existing table (Users).- Foreign Key

Here it is the zip (primary key of zips)

2NF: more>>

3rd Normal Form
   
   You should have already applied 2NF;
   Columns should depend only on the PK and non other than the PK.

                                                                                                                             3NF: more>>

There are lot of things you want to do in a day, like learn french, do the rest of the system and go site seeing. So you got to choose..
BTW when you don't have a choice, you got to be sure about the shortest path!

So.. How to do a system in 25 days? and make it worthwhile for a one year project..
Well, I know lot of people have the same problem. Hang on then. LessDoIT!

THE METHOD

Few days back I happened to came across a mysterious story, about a lost book of Archimedes;
Well, thought it might be interesting..

"This thirteenth century prayer book contains erased texts that were written several centuries earlier still. These erased texts include two treatises by Archimedes that can be found nowhere else, The Method and Stomachion. The manuscript sold at auction to a private collector on the 29th October 1998."

'Under-text' of the recycled parchment was identified as the work of Archimedes. I was taken by owe as they were uncovering the underline text after two layers of text. After decrypting this text they find unbelievable geometrical discoveries achieved by this great man who lived 2000 years ago. These include the approximation of 'pi' and finding the volume of a sphere and the roots of the modern calculus techniques and the concept of infinity. This text referred as 'the method' shows you how to think, not just the facts itself. Basis off almost all sciences known to mankind is bolstered on mathematics.Wonder how today would have looked like if these discoveries were known 100 or even 10 years before they were known??



If anyone is interested, you can find about the palimpsest here.
http://www.archimedespalimpsest.org/

Books on the net
http://math.nyu.edu/~crorres/Archimedes/Books/ArchimedesInternet.html

Read 'The Method'online
http://www.archive.org/stream/cu31924005730563#page/n5/mode/2up