First, the data dictionary

Data Stream Name: Borrowing Books

Alias: Library Doc

Introduction: the documents filled out by readers when they borrow books.

Source: readers

Where to go: review borrowing books.

Data flow: 250 copies/day

Composition: library card number+borrowing date+title+borrowing method+password+borrower?

Data Stream Name: Book Return

Alias: None

Introduction: The information attached when the reader returns the book.

Source: readers

Where to go: review and return books

Data flow: 250 copies/day

Composition: library card number+borrowing date+title+borrowing method.

Data storage name: book lending file

Alias: None

Description: library card number+borrowing date+title+borrowing method+password+borrower+operator.

Query requirements: it is required to be able to query and modify immediately.

Data storage name: inventory file

Alias: None

Description: Stores the information of books in and out of the warehouse.

Composition: book title+publisher+author+publication date+warehousing data+total quantity+(content introduction)+inventory before warehousing.

Organization: data file, indexed by title.

Query requirements: it is required to be able to query and modify immediately.

Processing Name: Check Library Card

Quantity: 1. 1

Reward conditions: get a library card.

Input: library card

Output: qualified library card

Processing logic: according to the borrowing documents and readers' library cards

What if? The library card number exists in the library file? And then what? Not expired? And then what? Is the password correct? then

The library card is valid.

Or what? Invalid library card