Data Dictionary Activity

Developing a data dictionary is critical to understanding the information that is present in a city’s 911 dataset.

What is a data dictionary?

A data dictionary describes the data stored in a database. In simple terms, it provides information and insights about your database, in other words, a data dictionary is a documentation for all the data assets in a database.

It is a repository of all column descriptions along with metrics describing the characteristics of the column as well like: mean, median, missing values, etc.

Some basic criteria for a data dictionary include:

Data source (data warehouse, data lakes, databases, applications)
Tables names and descriptions
Table relationships
Number of columns, column name, and descriptions
Data types
Sample data for the first few rows

(Source: https://atlan.com/what-is-a-data-dictionary/)

Some cities have full or partial data dictionaries for their 911 datasets. But for many, we will need to develop our own. This activity includes the steps involved for a Brigade to develop a data dictionary for their city’s 911 dataset if one is not already provided.

Below is a sample of the information we are looking to define in the data dictionary.

COLUMN	LABEL	TYPE	DESCRIPTIONS	UNKNOWNS	ASSUMPTIONS
The exact name of the column from the dataset	A human friendly column name	Is the contents of this column a number, free text, a multiple choice set (an enumeration), etc.	A fairly precise, plain english description of this column and the data it contains.	Describe ambiguous areas or aspects of the column that might be confused with other similar columns.	What assumptions seem reasonable to make about this column? Or what assumptions are you proposing?
EXAMPLE: DISP_CODE	EXAMPLE: Disposition Code	EXAMPLE: Text, date, date and time	EXAMPLE: A single digit field that reflects how the call was cleared. Clearing a call is also referred to as giving a disposition on a call. Examples of dispositions include "Accident Report", "No Action Required", "Departmental Report", etc."	EXAMPLE: Unclear who is responsible for choosing the disposition code	EXAMPLE: Presumably it is the police officer responding to the call who chooses the disposition code because this dataset is provided by the [City] Police Department.

What are the benefits of a data dictionary?