Design Library Management System
What is a Library Management System?
A Library Management System is software used to manage the operations of a library, such as tracking books, managing inventory, handling book checkouts and returns, maintaining user records, and enforcing due dates and fines.
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It helps librarians and users efficiently organize and access library resources.
In this chapter, we will explore the low-level design of a library management system in detail.
Lets start by clarifying the requirements:
1. Clarifying Requirements
Before starting the design, it's important to ask thoughtful questions to uncover hidden assumptions and better define the scope of the system.
Here is an example of how a conversation between the candidate and the interviewer might unfold:
Candidate: What kinds of items does the library lend? Only books, or other formats too?
Interviewer: Books are the main item, but the catalog also holds magazines. The design should make it easy to add new item types later.
Candidate: Can an item have multiple copies, and should each copy be tracked individually?
Interviewer: Yes. An item can have several physical copies, and each copy is borrowed and returned on its own, so track each one separately.
Candidate: What actions can a member perform?
Interviewer: A member can borrow an available copy and return it later. Members should also be able to search the catalog.
Candidate: What happens when every copy of an item is already borrowed?
Interviewer: The member can place a hold on the item. When a copy is returned, the member who placed the hold should be notified that it is available.
Candidate: How should search work?
Interviewer: Members should be able to search by title and by author or publisher. Keep search flexible so new criteria can be added without rewriting existing code.
Candidate: Do we need borrowing limits, due dates, or fines in the core design?
Interviewer: Leave those out of the core model for now. We will treat them as extensions once the main flows are in place.
After gathering the details, we can summarize the key system requirements.
- Support multiple item types in the catalog, such as books and magazines, with room to add more types later.
- Track multiple physical copies of the same item as separate entities, each with its own availability status.
- Allow adding items to the catalog along with a given number of copies.
- Register members who can borrow items.
- Members can borrow (check out) an available copy and return it.
- When no copy of an item is available, a member can place a hold and be notified once a copy is returned.
- Members can search the catalog by title or by author/publisher.
- Modularity: The system should follow object-oriented principles with clear separation between concerns like member management, catalog management, and borrowing
- Extensibility: The design should make it easy to add new item types, search criteria, and copy states without changing existing code
- Maintainability: The system should be easy to test, debug, and enhance over time
After the requirements are clear, let's identify the core entities/objects we will have in our system.