Overview
ISO/IEC 14568:1997 - "Information technology - DXL: Diagram eXchange Language for tree-structured charts" defines a text-based interchange language (DXL) for exchanging tree-structured charts among CASE tools. The standard specifies the semantics and syntax of DXL, using a Backus‑Naur Form (BNF)-style metalanguage, and targets interoperability of algorithm and program-structure diagrams without prescribing graphical presentation or data declarations.
Key topics and requirements
- Language scope: DXL is designed for exchanging tree-structured charts, including ISO/IEC 8631‑compliant program constructs and well‑structured ISO/IEC 5807 flowcharts (when they contain no data definitions).
- Syntax and semantics: The standard defines lexical elements, tokens, identifiers, specifications, comments and format-effectors. Syntax notation is BNF-derived and includes tabled meta-symbols and two compliance levels (level 0 and level 1).
- Module packet structure: An exchange unit is a Module Packet containing:
- Profile paragraph (code set, max string lengths, chart type, compliance level)
- Module Identification paragraph (unique module identifier and descriptive metadata)
- Module Algorithm paragraph (the tree-structured algorithm described as statements)
- Statement types: DXL formalizes imperative, blocked, serial, parallel, iterative, selective-choice and termination statements mapped to program constructs from ISO/IEC 8631.
- Exclusions: The standard explicitly does not specify graphical rendering (shape/size/location), configuration metadata (version, author, filename), or data structure/declaration/IO semantics for the algorithm’s data.
- Annexes: Informative annexes provide examples (A), correspondences to ISO/IEC 8631 program constructs (B), and DXL’s position relative to other standards (C).
- Normative references: Character sets and related standards (e.g., ISO/IEC 8631, ISO/IEC 5807, ISO/IEC 10646) are referenced for encoding and construct mapping.
Applications and who uses it
DXL is useful where tool interoperability and reuse of design artifacts matter:
- CASE tool vendors: implement DXL import/export to enable exchanging tree-structured charts between products.
- Software architects & designers: convert diagrams between notations while preserving algorithm structure.
- Systems integrators & toolchain engineers: automate transformations of program-flow and algorithm charts in development pipelines.
- Legacy modernization teams: migrate or reuse existing chart data across tools without re-authoring diagrams.
Related standards (high relevance)
ISO/IEC 14568:1997 delivers a practical, neutral format for exchanging tree-structured algorithm diagrams, enabling interoperability across CASE tools while avoiding constraints on visual rendering or data modeling. Keywords: DXL, Diagram eXchange Language, ISO/IEC 14568, tree-structured charts, CASE tools, program constructs, diagram exchange.