Command

As explained in Architecture Modernization: Socio-technical alignment of software, strategy, and structure

A command is an instruction requesting that a system or subsystem perform an action that may change state.

A command requests an action from a system or subsystem. In a domain message flow, its scope should reflect the requirements: one command can carry all information needed to complete an activity when the domain treats it as all-or-nothing. section 12.2.2

Completing a vehicle inspection

Complete Inspection carries the information needed to generate purchase advice. A single command fits the all-or-nothing requirement; separate commands for inspection results, images, and diagnostics are unnecessary unless requirements call for them. section 12.2.2

Figure 12.10 Step 2: completing the inspection

See the message-flow model showing the step that completes the inspection. section 12.2.2

How Architecture Modernization: Socio-technical alignment of software, strategy, and structure covers it

How deep it goes

Works through command scope and its requirements-based rationale, while deferring technical verification to a possible code probe.

Examples

Illustrates one Complete Inspection command carrying inspection results, images, and vehicle diagnostics.

What you can do after

Apply it via Domain Message Flow Modeling to choose command boundaries that fit the stated requirements.

How it connects

Ties commands to domain requirements, events, subsystems, and evolving domain boundaries.

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Also explained in

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  Learn PowerShell in a Month of Lunches: Fourth Edition, Covers Windows, Linux, and macOSA command is an executable instruction that a shell can invoke to perform an operation.
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  Idiomatic RustThe command pattern encapsulates an action as an object or value so its execution can be separated from the receiver and controlled in order or timing.
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  Apache Kafka in ActionA command is a message that requests another system to perform a specific action.

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Related concepts

• eventcontrasts with · An event is an occurrence, change, or associated record or notification recognized as significant within a system or context.
• SQLcontrasts with · SQL is a standardized declarative language for defining, querying, and manipulating data and structures in relational database systems.
• messagekind of · A message is a discrete unit of information or data represented, processed, or exchanged in a communication context.
• shell scriptused by · Bash is a Unix command-line shell and scripting language for executing commands interactively and through scripts.

This explainer was generated by Manning's knowledge graph from the text of Architecture Modernization: Socio-technical alignment of software, strategy, and structure. The section links point to the parts of the book it draws on.