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The week before I left my hometown to get back to Islamabad, my old school principle insisted me on paying a visit to my old school. I couldn’t refuse her. So there was I standing at the very place where my life began. It was a chilly Friday afternoon and the students had left for their homes at noon. I was roaming from one empty classroom to another, bumping into teachers and exchanging greetings. Every nook and corner that I visited reminded me of my old friends and all the memories started playing like a movie in front of my eyes.
I stepped into our library. And just how a typical SE
analyst would react, my instant reaction to the manual library management was
‘Damn! You still perform all the functions manually?’ The librarian turned back
to respond, “Yes Ma’am!” recognized me and smiled warmly to welcome me. I
walked ahead, exchanged few greetings and quickly resumed our discussion on the
topic. When asked, he told me that the school library still records information about the books, the
library members and transactions such as issuing and returning books in ledgers
and registers. Like other manual
information systems, this system faces many data-related issues such as data
redundancy, delayed retrieval of data, data corruption and inefficiency. As the
number of members is increasing, maintaining manual records has become a
difficult task for him. Searching for a particular record is equally difficult
and time consuming. For instance, when he needs to know about the status of a
book (whether it is issued or not), he has to manually traverse all the records
one by one to find if that book has been issued/returned/not issued. Moreover,
manually producing the reports for the issued books, the books in the library, members,
or accounts becomes cumbersome because there are hundreds and thousands of
records to go through.
This is one
instance of the manual systems that you’ll encounter in your SE field and that
you’ll have to find solutions for. To help us understand the functionality of such
a system, analyse it and find software solutions for it, we take help of system
modelling! One of the major components of the System Specification Stage
of SDLC is the system modeling. Now the name sufficiently explains what it is
about, modeling the system is the process of developing abstract views of an
existing system or a proposed system. How about we find software solutions for
my old school’s library system through system modeling? If you are interested,
let’s go ahead!
Choosing a Model Type
To model our existing library system, we need to choose the model type that will help us clarify what the existing system does and use it as a basis for discussing the existing system’s strengths and weaknesses. This will lead us to understand the requirements for the new system.
Each of these model types can be implemented using different UML diagram types. Don’t know what UML diagrams are? Don’t worry, we’ll explain. UML stands for Unified Modeling Language. <definition>
When you want to illustrate the operational context of a system, system
boundaries are established to define what is inside and what is outside the
system.
In the interactive models, we can model either the system-to-system
interaction or the component interaction using Use cases and sequence diagrams. Each use case
represents a discrete task that involves external interaction with a system. Actors
in a use case are people or other systems involved in those interactions. For
example, the Use Cases for our Library Management system are Add a New Member,
Edit Member details, Add a New Book, Edit Book details, Issue a Book, Return a Book and Pay Fine.
Similarly, Sequence diagrams are part of the UML and are used to model the interactions between the actors and the objects within a system. (Learn more about Use Cases here and Sequence diagrams here)
The class diagram will show all the classes in a system and
the associations between these classes. Lastly, State diagrams can be used to
define Behavioral models. These are models of the dynamic behavior of a system
as it is executing. They show how the system reacts to internal and external
events.
So now, you have seen how many different ways are available
to you to model a system using UML.
Planning the Proposed
System
From activity diagrams to use cases, all the UML diagrams
are easy to use and help you understand the working of a system and come up
with the requirements for the new system.. In our existing system, the librarian recorded the details about the
books and the library members and transactions such as issuing and returning books
in ledgers and registers. Using the
system modelling, we concluded that our proposed system can be an
object-oriented system.
Every new
member fills a standardized form and gives his personal information such as his
full name, address, contact number, CNIC number to the librarian. The librarian
updates the database with the new member’s details using a member class
instance and issues him a membership card and a member_ID. Similarly, Every new
book purchased for the library is given a Book_ID and its details such Book
Title, Author Name, Publisher, SSDN etc are recorded in a Books Relation using
the Book Class instances. Whenever a member wishes to issue a book , the
issue_book function is called. It checks the Members Relation to ensure that he
has returned the previously issued book.
Final Words
See how easy it was?
For drill, you can study these UML diagrams further and come up with the
rest of the functional requirements of the proposed Library Mgt System
yourself.
What we learnt today:
- What is System modeling?
- What is Unified Modeling Language (UML)?
- How does system modelling help the analyst to understand the functionality of the system?
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