---
title: "Book store process model"
subject: "Software Engineering"
chapter: 2
key: "semester_5/software_engineering:book-store-process-model"
source: https://www.bctengineer.com/q/semester_5/software_engineering/book-store-process-model
site: BCT Engineering
---

# Book store process model

Software Engineering · Chapter 2: System model

- Asked in: 2069 Chaitra, 7 marks
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/software_engineering/book-store-process-model
- Whole chapter: https://www.bctengineer.com/md/semester_5/software_engineering/chapter-2

## Question

Bhrantipur Book Store is popular among engineering students within the city of Bandhapur, as they have good reputation of making available of the reference books very efficiently through their books inventory system. Their reputation is mainly because of their close coordination with engineering schools. The various departments submit initial data about courses, instructors, textbooks and projected enrollments to the book store on a reference-book master list. The book store then generates a purchase order, which is sent to publishing companies that supplies the books. Book orders arrive at the bookstore accompanied by a packing slip, which is checked and verified by the receiving departments of engineering schools. When they pay for the books, the students are given a sales receipt. Following the details of the book order, inventory and sales processes prepare a system level process (behavior) model diagram for above scenario with clear statement of any assumptions that you have made.

## Short answer

Assumptions: system is book inventory system; departments, publishers, receiving department, students are external entities; departments send master list per semester; order quantity = projected enrollment minus stock; receiving verifies packing slip; students pay at counter; stock updated on receipt/sale. Context diagram shows external entities and data flows. Level-1 DFD processes: prepare master list, generate purchase order, receive/verify books, sell books. Data stores: book master list, purchase orders, inventory, sales.

## Answer

A system-level process (behaviour) model for this scenario is best shown as a **Data Flow Diagram**: a context diagram for the whole store and a level-1 DFD for the book order, inventory and sales processes.

#### Assumptions
1. The system is the book store's **book inventory system**; departments, publishers, the receiving department and students are outside it (external entities).
2. Each department sends one reference-book master list per semester with course, instructor, textbook and projected enrolment data.
3. Order quantity = projected enrolment − books already in stock (read from inventory).
4. The receiving department checks the packing slip against the purchase order and returns a verified slip (or a list of discrepancies).
5. Students pay at the counter (cash or card); payment details are not modelled further.
6. Stock is increased when verified books are received and decreased when books are sold.

#### Context diagram (level 0)

```text
                course, instructor,
 +-------------+ textbook, enrolment  +------------+
 | Departments |--------------------->|            |
 +-------------+                      |            |
                    purchase order    |    Book    |
 +-------------+<---------------------| inventory  |
 | Publishers  |--------------------->|   system   |
 +-------------+ books + packing slip |            |
                                      |            |
 +-------------+  packing slip        |            |
 | Receiving   |<---------------------|            |
 | department  |--------------------->|            |
 +-------------+  verified slip       |            |
                                      |            |
 +-------------+  payment             |            |
 |  Students   |--------------------->|            |
 |             |<---------------------|            |
 +-------------+  sales receipt       +------------+
```

#### Level-1 DFD

```text
+-------------+
| Departments |
+-------------+
      | course, instructor, textbook,
      | projected enrolment
      v
+------------------+        ======================
| 1.0 Prepare      |------->  D1 Book master list
|   master list    |        ======================
+------------------+                  |
                                      | books needed
      +-------------------------------+
      v
+------------------+  stock   ======================
| 2.0 Generate     |<-------    D3 Inventory
|  purchase order  |          ======================
|                  |  PO      ======================
|                  |------->    D2 Purchase orders
+------------------+          ======================
      | purchase order
      v
+-------------+
| Publishers  |
+-------------+
      | books + packing slip
      v
+------------------+ slip    +-------------+
| 3.0 Receive and  |-------->| Receiving   |
|   verify books   |<--------| department  |
+------------------+verified +-------------+
      | quantity received
      | (PO read from D2, stock added to D3)
      v
+------------------+ receipt +-------------+
| 4.0 Sell books   |-------->|  Students   |
|                  |<--------|             |
+------------------+ payment +-------------+
      | sale record --> D4 Sales
      | quantity sold --> D3 Inventory (reduce)
```

#### Description of processes

| Process | Input | Output | Data stores |
|---|---|---|---|
| 1.0 Prepare master list | Course, instructor, textbook, enrolment data | Master list entries | Writes D1 |
| 2.0 Generate purchase order | Books needed, current stock | Purchase order to publisher | Reads D1, D3; writes D2 |
| 3.0 Receive and verify books | Books + packing slip, verified slip | Stock update | Reads D2; updates D3 |
| 4.0 Sell books | Book request, payment | Sales receipt | Writes D4; updates D3 |

#### Data stores
- **D1 Book master list** – course, instructor, title, author, required quantity.
- **D2 Purchase orders** – PO number, publisher, titles, quantities, status.
- **D3 Inventory** – ISBN, title, quantity in stock, price.
- **D4 Sales** – receipt number, date, student, books sold, amount.

#### How the model shows behaviour
- The flows run in business order: master list → purchase order → delivery and verification → sale. This order is the system's behaviour over one semester.
- **Inventory** (D3) links all processes: 2.0 reads it to decide how many books to order, 3.0 adds stock and 4.0 reduces it.
- An unverified packing slip (missing or damaged books) stops the stock update in 3.0 and is reported back to the publisher; this exception is part of the assumed behaviour.

The model covers the three main business processes: **ordering** (1.0, 2.0), **inventory** (3.0 and the D3 updates) and **sales** (4.0).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which model does the answer use as the system-level process (behaviour) model?
   A. Data Flow Diagram (context plus level-1)
   B. Class diagram
   C. ER diagram only
   D. State transition table
   Answer: A. A context diagram and a level-1 DFD show the processes and data flows for ordering, inventory and sales. (Key point: Choice of model)

2. Which are treated as external entities in the model?
   A. Inventory and Sales data stores
   B. Departments, publishers, the receiving department and students
   C. Purchase order and sales receipt
   D. Process 1.0 to 4.0
   Answer: B. The system is the book store's inventory system, so the parties it exchanges data with are outside it. (Key point: External entities)

3. According to the stated assumptions, how is the order quantity found?
   A. Projected enrolment minus books already in stock
   B. Projected enrolment plus stock
   C. Number of instructors times 10
   D. Last year's sales only
   Answer: A. Process 2.0 reads the stock from inventory and orders projected enrolment minus current stock. (Key point: Order quantity assumption)

4. How does the D3 Inventory store link the processes?
   A. Only process 4.0 uses it
   B. It is read by 2.0 to decide order size, increased by 3.0 on receipt and reduced by 4.0 on sale
   C. It is written only by the departments
   D. It stores the sales receipts
   Answer: B. Inventory is read by 2.0, increased in 3.0 and reduced in 4.0, tying ordering, receiving and selling together. (Key point: Role of inventory store)

5. What happens in the model when the packing slip is not verified (missing or damaged books)?
   A. Stock is increased anyway
   B. The sale is cancelled
   C. The stock update in 3.0 stops and the problem is reported back to the publisher
   D. The master list is deleted
   Answer: C. This exception is part of the assumed behaviour: no stock update, and the discrepancy goes to the publisher. (Key point: Unverified packing slip)

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