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Software Architecture Guide

BPMN Conversation Diagram

Explanation

Section titled “Explanation”

A BPMN conversation diagram gives a “30,000-foot view” of how participants interact. BPMN is a standard notation for drawing business processes (see BPMN 2.0 Notation). A participant is a party in the exchange, drawn as a pool. Pools are explained in BPMN Swimlane (Pool and Lane).

The diagram shows the messages that pass between those participants. It presents them as conversation objects instead of individual messages.

Notation rules

  • A conversation is a hexagon drawn with a single thin line.
  • A sub-conversation is also a hexagon with a single thin line. It adds a small square marker with a plus sign inside.
  • Conversation links are drawn with double thin lines.

The plus marker tells the reader that a hexagon is a sub-conversation, not a plain conversation.

For the notation that shows full message flows, see BPMN Collaboration Diagram. For an overview of all BPMN diagram types, see BPMN Diagram Types.

Example

Section titled “Example”

Imagine an online shop, a payment provider, and a delivery company. One hexagon, labeled “Order payment,” links the shop and the payment provider. A second hexagon, labeled “Shipping,” links the shop and the delivery company. A reader sees who exchanges messages with whom, without reading any message detail.

Trade-offs

Section titled “Trade-offs”

The diagram stays at a coarse level. It shows conversations between participants, not the detail of each message. The verified facts say nothing further about when to prefer it over other BPMN diagrams.

Checks

Section titled “Checks”
  • Conversations are drawn as hexagons with a single thin line.
  • Sub-conversations carry a small square marker with a plus sign.
  • Conversation links use double thin lines.
Section titled “Related”

Sources

Section titled “Sources”