ISO 5806:1984

Overview

ISO 5806:1984 - Information processing - Specification of single‑hit decision tables - defines a standard format and conventions for single‑hit decision tables used in the documentation of computer‑based information systems. It specifies definitions (conditions, actions, rules, stubs, headings), the basic table layout, entry types, interpretation methods and recommended practices for preparing and simplifying decision tables. Note: multiple‑hit decision tables and other non‑documentation uses (e.g., program statement representation) are outside the scope.

Key Topics and Requirements

• Scope: Applies to single‑hit decision tables where each possible combination of conditions matches one, and only one, rule.
• Table format: The body is divided into four parts (table heading, condition stub, condition entries, action entries) with clear separation between condition and action areas. Rules are represented as columns.
• Definitions: Standardized terminology for condition, action, rule, condition stub, action stub, table heading, and initialisation section.
• Condition and action entries:
  • Limited entries: e.g., Y/N for conditions, X to mark actions to be executed.
  • Extended entries: textual values or codes that complete an otherwise incomplete specification (codes must be cross‑referenced).
  • Irrelevant or impossible entries can be marked with a dash (or “#”).
• ELSE‑rule: Optional default rule that applies to all combinations not covered by other rules; its use makes a table automatically complete but requires care to avoid masking omitted rules.
• Relationships between tables: Sequence, selection, repetition, nesting - and combinations thereof - with guidance on pointer actions between tables.
• Interpretation methods: Columnar (compare case against rule columns) and linear (sequential condition testing) methods to find the unique satisfying rule.
• Completeness and preparation: A table must be complete (or include an ELSE rule). Annex A recommends drafting full permutations of condition entries first, methods for splitting large tables, and simplification techniques where mutual exclusivity exists.

Applications and Users

ISO 5806 is practical for:

• Systems analysts and designers documenting decision logic in requirements and design artifacts.
• Software engineers and architects producing clear, testable decision specifications.
• Business analysts and process modelers capturing business rules.
• Technical writers and documentation teams standardizing system documentation.
• QA engineers and auditors using unambiguous decision tables for test case derivation and compliance reviews.

Keywords: ISO 5806, single‑hit decision tables, decision table format, information processing, documentation, condition entries, action entries, ELSE‑rule, table relationships.

Related Standards

• ISO 2382 (Data processing - Vocabulary), referenced for fundamental terms and programming terminology.