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Software Architecture Guide

Modeling Tool vs. Drawing Tool

Explanation

Section titled “Explanation”

A modeling tool stores architecture elements in a central repository. Each element exists once, and many diagrams can show it. The C4 model site describes this as treating the architecture model as a data structure that you can visualize in different ways.

When you change an element in a modeling tool, every diagram that uses it shows the change. A vendor guide says elements can also be shared across diagrams and even across projects.

A drawing tool (a graphics editor) works differently. It does not understand the syntax or meaning of a diagram, so it cannot enforce notation rules. A reused element is only a disconnected copy. You must update each copy by hand, and the diagrams can drift apart.

Text-based tools are another option. PlantUML is a free tool that renders sequence diagrams from text. You can version and merge that text like source code. See the articles Diagrams as Code and Documentation as Code.

The arc42 authors prefer real modeling tools over graphics editors, mainly for better model consistency. They also warn that modeling tools often have many functions but limited usability. They advise using a modeling tool only for the graphical part of the documentation. Most modeling tools lack built-in arc42 support, so you must create the arc42 structure yourself. arc42 offers a basic, not very elaborate, model template for Sparx Enterprise Architect.

The C4 model site adds that changes at scale are hard with diagramming tools but easy with modeling tools.

Example

Section titled “Example”

A team documents an online shop. The “Order Service” appears in a context diagram, a building block diagram, and a runtime diagram. The team renames it to “Order Management.”

With a modeling tool, they rename the element once, and all three diagrams show the new name. With a drawing tool, they open each diagram and edit each copy by hand. If they miss one, the diagrams disagree.

Trade-offs

Section titled “Trade-offs”

Modeling tools give better consistency and can enforce notation rules. The price is poor usability in many products and extra setup, such as building your own arc42 structure. Drawing tools are free of that overhead, but consistency and correct syntax depend entirely on the author. Text-based tools let you version diagrams like code. The facts here do not compare tool costs, licensing, or team-size fit.

A modeling tool generates views from one model. A drawing tool holds separate, unlinked drawings.

Diagram source 
flowchart LR
  subgraph Modeling tool
    M[(Central model)] --> V1[View A]
    M --> V2[View B]
    M --> V3[View C]
  end
  subgraph Drawing tool
    D1[Drawing A]
    D2[Drawing B]
    D3[Drawing C]
  end

Checks

Section titled “Checks”
  • The documentation states whether diagrams come from a central model or from independent drawings.
  • If a drawing tool is used, the team has a manual way to keep reused elements consistent across diagrams.
  • If a modeling tool is used, it is limited to the graphical part of the documentation.
  • If text-based diagrams are used, the source text is versioned like source code.
Section titled “Related”

Sources

Section titled “Sources”