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NPCR–AERRO Diagram Conventions

The Advancing E-cancer Reporting and Registry Operations (AERRO) model diagrams are based on the Unified Modeling Language (UML). This document outlines additional conventions used specifically for AERRO.

General Conventions

  • Diagrams flow from top to bottom.
  • Diagrams flow from left to right.
  • The version number changes only when major changes are implemented. For minor changes, there is no version change.
  • Notes are represented by rectangles with the top right corner folded down.
  • The work being discussed is shaded purple.
  • General comments or questions are shown in white or purple colors.

Decision Nodes in Activity Diagrams (Workflow and Data Flow Diagrams)

  • Text questions are to the left of the decision node.
  • All activity diagrams (in general) have one start point and one end point.

Use Case Diagrams

  • The first level is represented as a package. A package is a container in the shape of a yellow folder which can contain different model elements such as use cases and other packages.
  • Second-level use cases are represented by light blue ovals.
  • Each use case is assigned to the first or second level according to its hierarchy.

Activity Diagrams (Workflow and Data Flow Diagrams)

  • Decisions are represented by light yellow diamonds.
  • Start and end nodes are represented by black circles with a red outline.
  • State transition specifications are presented as a guard condition for transition from one state to another.
  • Business rules and software requirements are shown in the right swimlane (column) in light blue.
  • Horizontal and vertical solid black lines are synchronization bars.

Technicalities and Concepts to Understand the Diagrams

  • Domain Diagram: The classes connecting to "Internal and External Data Source" classes are actual data sources, not data coming from those classes.


  • Use Case Diagram: The use cases are presented in a hierarchical way. The highest or first-level use case consists of the second-level use case(s) and so on.


  • Workflow Diagram: The details presented in this diagram are limited. It is a simple representation of the normal course of events.


  • Data Flow Diagram: This is a detailed diagram with all conditions covered for a use case or process. It presents exceptions, alternate courses of events, and business rules for the normal course of events in the process.


  • All Diagrams: When reading a diagram, pay attention to the direction of arrows.
Page last reviewed: January 12, 2009
Page last updated: January 12, 2009
Content source: Division of Cancer Prevention and Control, National Center for Chronic Disease Prevention and Health Promotion
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