← VCE Software Development U3O1

Writing a data dictionary entry

One data dictionary row for a data item: name, data type, format or size, description, example value and validation rule. Written from a requirement or IPO chart.

Part of: VCE Software Development - U3O1 - Programming — Module 11, VCE Software Development - U3O2 - Analysis and Design — Module 95, VCE Data Analytics - U3O1 - Data Analytics — Module 30, QCE Digital Solutions Unit 2 — Data-Driven Problems and Solution Requirements — Module 59, WA Computer Science ATAR Year 11 — Data Management — Module 40

Understanding Writing a data dictionary entry in VCE Software Development U3O1

What it does: A value with a decimal part needs the float data type, and the row shows this in the type column and in the 1 decimal place format. The last column of the row holds the range check taken from the IPO chart, so the allowed values 7 to 12 are written there. Age is a whole number, so integer is the right type. The row also has a clear name, a format, an example and a validation rule. Prices have cents, so they are not whole numbers. A float stores decimal values, while an integer would lose the cents. The description says what the data item means in the problem. 'A number' repeats the type and tells the reader nothing about the purpose.

Common mistakes: An age is a whole number, so its format is digits, not letters. The line should be 'Format: 2 digits'. The example value must be a real value of the float data type. It should be a number such as 12.50, not words.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

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This module's key terms are also in a printable crossword (Modules 10–47) and word search (Modules 10–71).

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Learning
Duo
A requirement says the system must store a student's age in years. Which data dictionary row is best?
studentAge | integer | 2 digits | age in years | 15 | 11 to 19age | text | 2 digits | age in years | fifteen | any value
Matches
studentAge | text | 2 digits | age in years | 15 | 11 to 19
↓
Wrong data type: age is a whole number used in a range check, so it should be integer, not text.
Applying
Meanings
Term
studentAge, integer, 2 digits, age in years, 15, 11 to 19
Meaning
One data dictionary row for a data item: name, data type, format or size, description, example value and validation rule. Written from a requirement or IPO chart.
Practice
studentAge | integer | 2 digits | age in years | 15 | 11 to 19
Testing
Gaps
studentAge | | 2 digits |
Check Answer
Spots
2Data type: integer
3Format: 2 letters

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Quick Questions

1. A requirement says the system must store a student's age in years. Which data dictionary row is best?
A. studentAge | integer | 2 digits | age in years | 15 | 11 to 19 ✓
B. age | text | 2 digits | age in years | fifteen | any value
Age is a whole number, so integer is the right type. The row also has a clear name, a format, an example and a validation rule.
2. An IPO chart lists the input 'item price in dollars, such as 4.50'. Which data type should the data dictionary row use?
A. integer
B. float ✓
Prices have cents, so they are not whole numbers. A float stores decimal values, while an integer would lose the cents.
3. Which entry describes the format or size of a student ID such as 'S1042' (one letter followed by four digits)?
A. A whole number
B. 5 characters: 1 letter then 4 digits ✓
Format or size says how the data looks and how long it is. 'A whole number' is a data type, not a format.
4. Which is a validation rule for a data item called quantityOrdered?
A. 1 to 100 ✓
B. Number of items the customer orders
A validation rule states which values are allowed, such as a range. The other option is a description.
5. A data dictionary row has the name 'student age' with a space in it. Which is the better name for the row?
A. studentAge ✓
B. student age
Data item names should follow a naming convention such as camelCase, with no spaces. This makes them easy to turn into variable names.

Match the Pairs

studentAge | integer | 2 digits | age in years | 15 | 11 to 19 → A complete data dictionary row: name, data type, format or size, description, example value and validation rule for a student's age
isEnrolled | Boolean | True or False | has the student enrolled | True | must be True or False → A data dictionary row that records a yes or no value as a Boolean, with the allowed values stated as its validation rule
Choosing the data type: a requirement says the system must store the student's average mark, such as 76.5, so the type column needs a number with decimals → averageMark | float | 3 digits, 1 decimal place | average mark across subjects | 76.5 | 0.0 to 100.0
Stating the validation rule: the IPO chart says a student's year level input must be a whole number from 7 to 12 → yearLevel | integer | 1 or 2 digits | school year level | 10 | 7 to 12
studentAge | text | 2 digits | age in years | 15 | 11 to 19 → Wrong data type: age is a whole number used in a range check, so it should be integer, not text.
firstName | string | up to 20 characters | student's first name | Ava | → The validation rule is missing: the last column is empty, so the row does not say what input is allowed, for example a length of 1 to 20 characters.

Key Term

studentAge, integer, 2 digits, age in years, 15, 11 to 19
One data dictionary row for a data item: name, data type, format or size, description, example value and validation rule. Written from a requirement or IPO chart.

Fill in the Blanks

1. studentAge | integer | 2 digits | age in years | 15 | 11 to 19
Hint: Type the data type that suits a whole-number age.
2. studentAge | integer | 2 digits | age in years | 15 | 11 to 19
Hint: Type the format or size, saying how many digits the value has.
3. studentAge | integer | 2 digits | age in years | 15 | 11 to 19
Hint: Type the validation rule: the range of accepted ages.
4. studentAge | integer | 2 digits | age in years | 15 | 11 to 19
Hint: Type the camelCase name of the data item, which comes from the requirement.
5. studentName | string | up to 30 chars | full name | Ava Nguyen | not empty
Hint: Type the data type used for text data.

Spot the Error

Question 1
A Name: studentAge
B Data type: integer
C Format: 2 letters
D Description: age in years
E Example: 15
F Validation: 11 to 19
Line C — An age is a whole number, so its format is digits, not letters. The line should be 'Format: 2 digits'.
Question 2
A Name: itemPrice
B Data type: float
C Example: twelve fifty
D Validation: 0.01 to 500.00
Line C — The example value must be a real value of the float data type. It should be a number such as 12.50, not words.
Question 3
A Name: isMember
B Data type: Boolean
C Description: member status
D Example: maybe
E Validation: True or False
Line D — A Boolean can only be True or False. The example should be 'Example: True' (or False).
Question 4
A Name: studentName
B Data type: integer
C Format: up to 30 characters
D Validation: not empty
Line B — A student's name is text, so the data type should be String, not integer.
Question 5
A Name: dateOfBirth
B Data type: Boolean
C Format: DD/MM/YYYY
D Example: 07/03/2009
E Validation: not in the future
Line B — A date of birth is a date, not a True/False value. The line should be 'Data type: Date'.

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