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Design
Software application design is the process of determining specifications of the software for it to accomplish certain goals within certain constraints. It is like developing a blueprint which will be used to build the software.
Computer program: a set of instructions telling a computer what to do
Programming language: in order for a computer to understand the instructions, they need to be written in a language the computer understands, that is, in a programming language like C, C++, Java
Software: the programs and other operating information used by a computer. Software can be made up of more than one program.
Types of software: there are 2 major types, application software (for performing user tasks like MS Word, online shopping apps) and system software (like Windows, macOS, which enable the applications to execute). Here we will consider only application software.
What is designing all about?
Welcome! This is an online shopping startup which is building an application for customers to buy a variety of products online. You will be working on assignments with their software engineering team.
Design requirement
Your team has to build the online shopping application which should have features like allowing users to view products, signup and place orders.
Design
Step 1: High level design
Determining architecture (structure) of the software application and its components
(high level design is done when developing a software from scratch or major redesign of existing one, and generally not for minor modifications)
We will now go through the design and development process step wise by first understanding the theory then implementing it on the requirement
Presentation Tier
This is the part of the application which user interacts with using devices like laptops, mobiles, tablets.
For example, in Signup feature the form in which user enters his details is in this tier.
The layout of the application interface seen by user is designed by user interface designers who are generally not software engineers hence it will not be covered in this tour.
Application (logic) tier
This part processes the commands, makes logical decisions, performs calculations, transforms data and moves it between the other 2 tiers.
In Signup feature, this tier checks if details entered by user meet the registration criteria.
Data tier
This part stores all the data required in the application like product list, orders placed, user details.
In Signup feature, if application tier determines all details entered by new user meet the criteria then these details will be stored in the data tier, to be used as needed.
Your team has decided that this software application will have above 3 tiers
(many types of structures are possible for an application software, this 3 tier type is just one of them)
Design
Step 2: Database design
Determining how to organise all the information required for the application in the database
(this is done for the data tier explained in previous step)
We will now go through the design and development process step wise by first understanding the theory then implementing it on the requirement
To handle customer orders following information needs to be stored in the database:
Customer_ID (numbers)
unique number assigned by the software to every customer
Order_ID (numbers)
unique number assigned by the software to every order placed by customer, for example if a customer places an order for 4 books today and another order for 3 books tomorrow then these will be considered as 2 separate orders having different Order_ID even though placed by same customer
Customer_FirstName (alphabets)
first name provided by customer
Customer_LastName (alphabets)
last name provided by customer
Order_Status (alphabets)
3 possible values: Pending, In-progress, Complete
this is assigned by the software to every order and will change with progress in order fulfilment
You need to determine how the above information should be organised into tables in a relational database, so that for a given Customer_ID the customer’s name as well as order data can be obtained easily, while occupying minimum storage space.
You will now begin working on the database design. This assignment should ideally take 10 minutes.
Step 1
In the assignment you can put different columns like Customer_ID and Customer_FirstName in a single table or in separate tables by creating new tables. You need to determine which columns need to be together and which need to be in separate tables for efficient storage.
Step 2
Ensure there is no unnecessary duplication of data in your arrangement.
Step 3
Ensure every table has a Primary Key column to uniquely identify every row of the table.
Step 4
Ensure different tables have a common column so all data for a customer can be obtained using only Customer_ID.
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