CBAP Tutorial - Data Dictionary TN

What is Data Dictionary?

Data dictionary is technique to define the meta data for a software project. BABOK also mentions this as a technique. So lets understand – What is data dictionary?

Data Dictionary Tutorial

IBM Dictionary of computing defines data dictionary as

“A centralized repository of information about data such as meaning, relationships to other data, origin, usage, and format”

A data dictionary is also referred to as metadata repository. It comprises of information about the primitive and composite data elements.

A landline number is an example of a composite data element and it comprises of primitive data elements like ISD Code, STD Code, Area code etc.

Let’s consider a complete telephone number in India, it looks as follows:

+91 22 2857 1200

This number comprises of multiple information:

Basic Element Name Any other name Type of values Description
ISD Code Country Code Number The international dialling code for the country
STD Code City Code Number The country’s city code
Area Code Area Code Number Local telephone exchange number
Number Telephone Number Number Actual phone number
Telephone Number =     ISD Code + STD Code + Area Code + Number

The table above describes primitive data elements and the composite data elements. This table is an example of data dictionary.

Purpose of Data Dictionary

Data dictionary is used to create a standardised representation of data elements for a given project or projects and for its stakeholders. This helps in having a common understanding and representation.

Without having a data dictionary, data can have multiple interpretations in a system. This may lead to different representations. For example, one developer may present a phone number as one value (allowing numbers and ‘+’ sign) and other one may present it as a combination of multiple fields. This leads to bad user experience.

Please note that data dictionary is always created for a context (a project). A composite data element may be relevant for one project but may not be for the other.

For example, if the application under development is for customers across the world, the ISD code is a relevant part of the telephone number. We have created the data dictionary for an application with ISD number.

But, if the application is to be used only in one country, the ISD code has no relevance and should not be part of the data dictionary.

 Formats for Data Dictionary

Multiple formats can be used to represent a data dictionary. One of the formats is used on the previous page. BABOK v3 guide uses the following format:

Elements of Data Dictionary

As per BABOK v3 guide, the primitive data elements should have the following information:

  • Name: A meaningful name to the element so that it be recognised uniquely.
  • Aliases: Alternate or commonly used term used for the data element, different from Name
  • Value/Meanings: Represents data types (like number or text), size, list of values (if applicable) etc
  • Description: More details about the data elements for the specific project/context

Composite Elements may be:

  • Sequences: A composite element comprises of multiple primitive data elements. These elements could be arranged in a sequence i.e. coming one after the other as in the telephone number. A ‘+’ sign is used to represent that as shown below:

[ISD Code + STD Code + Area Code + Telephone Number]

  • Repetitions: When one of the data elements gets repeated multiple times. A ‘{ }’ is used to represent that:

Invoice = Invoice_number + Date + {items-ordered} + Sub-total + Sales-Tax + Total due

  • Optional Elements: A composite data element may also have optional elements. Optional elements are represented by ‘( )’.

Customer_name = First_name + (Middle_name) + Last_name

Note: Care must be taken while creating the data dictionaries. Unnecessary and irrelevant data dictionaries can lead to limited or no realisation of business value.

Are you new to BABOK? You can read about the Business Analysis Core Concepts Model (BACCM). 

About Techcanvass

Techcanvass offers IT certification courses for professionals. We are an IIBA endorsed education provider (EEP), iSQI ATP (for Certified Agile Business Analyst Training) as well as Agile Testing alliance partner for CP-SAT certification training in Selenium.

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Abhishek Srivastava is a seasoned IT professional with diverse experience in Banking, Insurance, Utility and Education domains. Managing large accounts, Program management & Developing business solutions has been his forte. An NIT / IIM Kozhikode graduate, He founded Techcanvass (https://techcanvass.com) in 2013. With Techcanvass, He is pursuing his dream of creating an organization imparting quality education to IT professionals. He believes that learning is a lifelong journey and one must never stop learning. He also loves writing and sharing his knowledge. Some of his notable books are ERP to E2RP, UML Modelling for Business Analysts, Business Analysts Practitioners Guide, Software Testing: A practical Approach. All these books are available on Amazon.

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