How to use a standards reference
A specification defines conformance; a tutorial explains how to apply it. Start with the specification version claimed by the producer, validator or interface, then check the implementation’s documented feature set. A tool describing itself as “XSD compatible” or “JSON Schema based” is not precise enough when several versions and optional vocabularies exist.
Normative sections state requirements. Examples and notes help interpretation but do not create independent requirements. Errata, implementation reports and test suites can also affect a responsible deployment decision. xFront guides link design choices to these primary sources while keeping the specification as the final authority.
XML family
- W3C Extensible Markup Language defines XML document syntax, character handling and well-formedness.
- W3C XML Schema 1.1 Structures and Datatypes define the XSD 1.1 grammar and type system.
- W3C XPath 3.1 supplies the expression language used across modern XML technologies.
- W3C XSLT 3.0 defines rule-based transformations over the XDM data model.
- Schematron resources cover rule-based assertions and reports.
These standards form layers. XML parsing does not perform XSD validation, XSD validity does not prove a Schematron business rule, and transformation success does not establish compatibility with every consumer.
JSON and API contracts
- JSON Schema specification publishes dialect and vocabulary documents for evaluating JSON instances.
- OpenAPI Specification describes HTTP operations, parameters, representations, security and responses around schema objects.
OpenAPI 3.1 uses a JSON Schema dialect, but an OpenAPI document is not merely one large JSON Schema. Paths, operations, media types and security live in the surrounding interface model. Converters must therefore identify which layer they translate and which behavior has no representation at the destination.
Agent tool contracts
- MCP tool specification defines discovery and invocation of server-provided tools.
A machine-readable input schema is only part of an agent tool contract. Tool name, description, result structure, errors and safety semantics affect selection and use. Treat generated MCP metadata as a draft that requires review against the underlying operation rather than proof that the operation is safe for autonomous invocation.
Version and conformance policy
Record a precise standard or dialect version in source control with the schema and tests. Pin processors in continuous integration, because a new default dialect or XPath engine can change results without a schema edit. When a format has no in-document version marker, deployment configuration becomes part of the contract and must be reproducible.
| Claim | Evidence to retain |
|---|---|
| Document is valid | Schema release, processor/version and validation report |
| Conversion is lossless | Feature inventory plus bidirectional fixtures |
| Change is compatible | Consumer policy and old/new corpus results |
| Tool is callable | Interface schema, semantic review and failure tests |
Conformance tests and implementation reality
A product may conform to one profile while omitting optional features from the broader family. Review its conformance statement and execute the cases the project actually depends on. Passing one vendor’s examples is useful evidence but not a substitute for an independent corpus covering namespaces, references, error handling and boundary values.
When two processors disagree, reduce the case and compare it with normative language and published errata before selecting a workaround. Record the chosen interpretation and retain the reduced fixture. That turns an implementation surprise into a testable compatibility decision instead of an undocumented dependency on one product.
Links on this page point to the maintained specification families or their stable “latest” entry points. A contract should still record the exact dated or numbered release it implements rather than inheriting whatever document the latest URL serves in the future.