Enterprise Base Pattern Catalog

The 11 base patterns in Chapter 18 of Patterns of Enterprise Application Architecture are cross-cutting utility patterns that appear everywhere in enterprise application design. They are not architectural patterns (like Data Mapper or Front Controller) — they are the building blocks those patterns are built from. Every other PEAA skill references at least one of these.

This skill is a lookup-and-guide: identify the pattern by name or by problem description, then get the canonical definition, when to apply it, a modern language sketch, and any critical cautions.

When to Use

Use this skill when:

• Another PEAA skill says "introduce a Gateway here" or "this is a Value Object" and you need the definition.
• You're describing a cross-cutting utility problem: wrapping an external API, replacing null checks, making monetary arithmetic correct, isolating tests from external services, or breaking a package dependency cycle.
• You want to name a pattern you already know exists but can't recall precisely.
• You want the modern equivalent of a 2002-era base pattern.

NOT for: choosing among data-source patterns, domain logic patterns, web presentation patterns, concurrency patterns, or session state patterns. For those, see the dedicated selector skills in this set.