Data Dictionary and Element Attributes

Data Dictionary

• Contains information about data, including its meaning, relationships to other data, origin, usage, and format
• Includes data element descriptions, attribute/property definitions, relationship descriptions, rules and constraints, and other metadata

### Data Element Attributes

• Data element name, alias, type and length, default value, acceptable values, source, security, responsible user(s), and description/comments are documented
• The objective is to provide clear, comprehensive information about the data and processes that make up a system

Data Flows

• All data flows in the data dictionary must be documented
• Typical attributes include data flow name or label, description, alternate name(s), origin, destination, record, volume, and frequency

### Data Stores

• Every DFD data store in the data dictionary must be documented
• Typical characteristics of a data store include data store name or label, description, alternate name(s), attributes, and volume and frequency

Data Flow Diagrams (DFDs)

• Use various symbols to show how the system transforms input data into useful information
• Show how data moves through an information system but do not show program logic or processing steps
• A logical model that shows what the system does, not how it does it

Data Flow Diagram Symbols

• Use four basic symbols representing processes, data flows, data stores, and entities
• Several versions of DFD symbols exist (Gane and Sarson symbols are used in the textbook, Yourdon symbols are another popular set)

Process Symbols

• Contain business logic which transform data and produce the required results
• The process name on the symbol identifies a function consisting of a verb followed by a singular noun (e.g.: APPLY RENT PAYMENT)
• A process symbol can be called a black box because the process’s inputs, outputs, and functions are known, but underlying logic is hidden

Data Flow Symbols

•  Represents one or more data items
• Symbol is a line with a single or double arrowhead
• Data flow name includes a singular noun and an adjective (if needed)

Data Store Symbols

•  Represents data that the system stores because one or more processes need to use the data later
• Symbol is a flat rectangle that is open on the right side and closed on the left
• Data store name is a plural name consisting of a noun and adjectives (if needed)
• Must be connected to a process with a data flow

Entity Symbols

•  Symbol is a rectangle, which may be shaded to make it look three-dimensional
• Shows only external entities that provide data to the system or receive output from the system
• Also called terminators because they are data origins or final destinations
• An entity that supplies data to the system is called a source
• An entity that receives data from the system is called a sink

Logical and Physical Models

• A logical model shows what the system must do, regardless of how it will be implemented physically.
• Later, in the systems design phase, a physical model is built that describes how the system will be constructed.

This quiz explores the fundamental concepts of data dictionaries, including data element attributes, data flows, and data stores. Participants will learn about the essential components that define data structures and how they relate to each other. Gain insight into metadata, data relationships, and the significance of clear documentation in data management.