Written documentation is the least effective form of communication to create a
shared understanding. Often stakeholders see things differently than
developers do. Stakeholders sometimes see challenges and requirements
differently between one another.

Using diagrams when implementing Dynamics 365 or the Power Platform helps
create a shared understanding of requirements and vision for your
solution.

Some of the key reasons why diagrams work:

• Diagrams help visualize a system and promote a deeper understanding of the
  requirements.
• They act as visual templates to guide when configuring your Solution.
• They help to understand complex parts of the system, exposing opportunities
  for simplification.

Ideally, you want to co-create diagrams with your team. Keep your diagram as
lightweight and collaborative as possible. Down the track, you will know more
and will be able to fine tune them.

Use Case Diagram (UML)

A Use Case diagram is a graphical representation of the interactions between
an actor and a system. A use case is a great technique for quickly
identifying, clarifying, and organizing core system requirements.

I typically create a Use Case Diagram in the following situations:

• Initial meetings with stakeholders to get a quick understanding of the
  requirements
• First workshops to validate requirements (and making sure I didn’t miss
  anything obvious).

Conceptual Diagram

The Conceptual Diagram describes, at a high level, what are the main
functionalities of the solution. The colouring helps me group
functionalities of the same category.

The Conceptual Diagram is a constantly evolving diagram, that we tweak along
with the build and the lifecycle of the system.

Conceptual Diagrams help me explain how I understood the solution to
others. I use Conceptual Diagram in the following context:

Entity Relationship Diagram

An Entity Relationship Diagram (ERD) is a type of diagram that illustrates how
Dynamics 365 Entities (or “Tables) such as Contacts, Companies or Cases relate to each
other within the solution.

ERD helps to understand how the data is structured and how your Dynamics 365
Entity model will be designed.