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CODITECT Standard: Software Design Documents (SDDs)

Standard ID: CODITECT-STANDARD-SDD Version: 1.0.0 Status: Active Created: 2025-12-22 Author: AZ1.AI INC Architecture Team Compliance: Mandatory for all SDDs

1. Purpose​

This standard defines the requirements for creating Software Design Documents (SDDs) within the CODITECT ecosystem. SDDs describe the architecture and design of software systems at a level suitable for implementation.

2. Scope​

This standard applies to:

  • All SDDs in internal/architecture/ or docs/architecture/
  • System-level design documents
  • Component design specifications
  • API design documents

3. SDD Definition​

A Software Design Document (SDD) describes HOW a system is designed and structured. It bridges the gap between requirements (WHAT) and implementation (CODE), providing:

  • System architecture (C4 diagrams)
  • Component decomposition
  • Data models and schemas
  • API specifications
  • Integration patterns
  • Security design

4. When to Create an SDD​

4.1 Create SDD For​

TriggerExample
New system/subsystemInstallation system, LMS platform
Major architectural changeMigration to microservices
Complex featureMulti-tenant isolation
External integrationsPayment gateway, SSO
Infrastructure designCloud deployment architecture

4.2 SDD vs ADR​

DocumentPurposeFocus
ADRRecord a decisionWHY we chose X
SDDDescribe designHOW X is structured

5. Naming Convention​

5.1 File Naming Format​

{SYSTEM-NAME}-SDD.md

Examples:

  • CODITECT-CORE-SDD.md
  • INSTALLATION-SYSTEM-SDD.md
  • LMS-PLATFORM-SDD.md

5.2 Document ID Format​

AZ1-SDD-{DOMAIN}-{NUMBER}

Examples:

  • AZ1-SDD-CORE-001
  • AZ1-SDD-LMS-002

6. SDD Structure​

6.1 Required Sections​

Every SDD MUST contain:

  1. Executive Summary - High-level overview
  2. System Context (C4 Level 1) - External dependencies
  3. Container Diagram (C4 Level 2) - Major components
  4. Component Design (C4 Level 3) - Internal structure
  5. Data Model - Entities and relationships
  6. API Specifications - Interfaces and contracts
  7. Security Design - Authentication, authorization
  8. Deployment Architecture - Infrastructure

6.2 Optional Sections​

  • Code-level design (C4 Level 4)
  • Performance requirements
  • Scalability design
  • Migration strategy
  • Testing strategy

6.3 Template Reference​

Use template: CODITECT-CORE-STANDARDS/TEMPLATES/SDD-TEMPLATE.md

7. C4 Model Integration​

7.1 Required Diagrams​

LevelNameRequiredDescription
C4-1System ContextYESSystem and external actors
C4-2ContainerYESMajor deployable units
C4-3ComponentYESInternal components
C4-4CodeOptionalClass/module level

7.2 Diagram Format​

Use Mermaid for diagrams (GitHub-compatible):

8. Content Requirements​

8.1 Technical Depth​

SectionDepthExample
Executive SummaryOverview1-2 paragraphs
ContextRelationshipsExternal systems list
ContainersArchitectureDeployment units
ComponentsStructureClasses/modules
Data ModelSchemasEntity-relationship
APIsContractsOpenAPI/GraphQL

8.2 Quality Criteria​

  • Complete: All required sections present
  • Accurate: Reflects actual implementation
  • Current: Updated with changes
  • Consistent: Terminology matches codebase
  • Actionable: Developers can implement from it

9. Relationship to Other Documents​

9.1 Document Hierarchy​

Requirements (SRS/PRD)
    │
    ▼
Architecture Decisions (ADRs)
    │
    ▼
Software Design (SDD) ◄── YOU ARE HERE
    │
    ▼
Technical Design (TDD)
    │
    ▼
Implementation (Code)

9.2 Cross-References​

SDDs should reference:

  • Related ADRs for decisions
  • TDDs for implementation details
  • API documentation
  • Deployment guides

10. Versioning​

10.1 Version Format​

MAJOR.MINOR.PATCH
Change TypeVersion Bump
Breaking architectural changeMAJOR
New component or featureMINOR
Clarification or fixPATCH

10.2 Change Log​

Every SDD must include a changelog section:

VersionDateAuthorChanges
1.1.02025-12-22{Name}Added X component
1.0.02025-12-01{Name}Initial version

11. Storage Location​

TypeLocation
Core systemsinternal/architecture/system-design/
Subsystemsinternal/architecture/{subsystem}/
Distributiondistribution/*/technical-docs/

12. Review Process​

12.1 Before Publishing​

  • All required sections complete
  • C4 diagrams included (Levels 1-3)
  • Data model documented
  • API specifications included
  • Security design addressed
  • Cross-references valid

12.2 Maintenance​

  • Review quarterly or with major changes
  • Update when implementation diverges
  • Archive superseded versions
DocumentPurpose
SDD-TEMPLATE.mdSDD template
CODITECT-STANDARD-TDD.mdTechnical design standard
CODITECT-STANDARD-ADR.mdADR standard

Last Updated: 2025-12-22 Review Schedule: Quarterly Owner: Architecture Team, AZ1.AI INC