XSD 1.0 support

Supported means positive and negative behavior is covered by project tests. Partial means only the documented subset is implemented. Unsupported means zxsdc rejects the construct instead of ignoring it.

The API, ABI, and migration contract separately defines API/ABI epochs, generated format checks, memory configuration requirements, and migration rules. It does not change the supported XSD subset or promise full W3C conformance.

Schema structure and types

Feature	Status	Scope
xs:schema, global and local elements	Supported	Multiple roots, named, typed, anonymous, and global element references.
xs:complexType and xs:simpleType	Supported	Named and anonymous definitions.
sequence, choice, all	Supported	Nested particles and bounded or unbounded occurrences.
attributes	Supported	Optional, required, prohibited, form, default, fixed, and global references.
attribute ref	Supported	References preserve the global declaration namespace, type, and value constraint.
group and attributeGroup	Supported	Nested references, occurrences, namespace resolution, wildcard algebra, and legal self references in redefinitions; circular definitions are rejected.
simple restriction and facets	Supported	Enumeration, lengths, bounds, decimal digit limits, whitespace, and inherited restrictions.
xs:list and xs:union	Supported	Named and anonymous item/member types.
XSD 1.0 built-in simple datatypes	Supported	String/name, numeric, date/time, duration, binary, QName, URI, ID/IDREF, ENTITY, and lexical NOTATION families.
xs:notation declarations	Supported	Public/system metadata and namespace-aware enumerated NOTATION values.
type extension and restriction	Supported	simpleContent and complexContent with inherited content/attributes.
abstract types	Supported	Direct use is rejected; valid derived runtime types are accepted.
recursive type definitions	Supported	Direct and mutual named complex types plus guarded recursive global element references, bounded at runtime by ZXSD_MAX_DEPTH.
xs:anyType and mixed content	Supported	Interleaved text, lax arbitrary content, implicit element types, and restrictions.

Namespaces and composition

Feature	Status	Scope
target namespaces and QName resolution	Supported	Qualified and unqualified local declarations.
elementFormDefault / attributeFormDefault	Supported	Per-declaration form overrides.
xs:include and xs:import	Supported	Explicit local resolution only; implicit network access is forbidden.
xs:redefine	Supported	Type, model-group, and attribute-group redefinitions with original-component self references.
resolver callback and schema registry	Supported	Search paths, namespace registry, and circular-dependency detection.
substitution groups	Supported	Type derivation, abstract heads, block, and final are checked.
annotations and foreign metadata	Supported	Validated while compiling, then omitted from generated descriptors.

Instance validation

Streaming validation uses occurrence counters for eligible flat models and a shared, bounded continuation pool for nested sequences/choices and complex repetitions. Alternative occurrence partitions are retained and merged, not chosen greedily. ZXSD_STREAM_MODEL_CAPACITY bounds this shared workspace; exhaustion or excessive epsilon work reports ZXSD_ERR_STREAM_LIMIT. Setting it to zero selects the old bounded-history matcher for non-flat models. ZXSD_STREAM_CHILD_CAPACITY limits only that fallback’s child history, not repetitions processed by an incremental model.

Feature	Status	Scope
xs:any and xs:anyAttribute	Supported	Namespace constraints and strict, lax, or skip processing.
unique, key, keyref	Supported	Bounded tuple storage suitable for embedded targets.
identity XPath	Supported	XSD restricted child/descendant/attribute paths, wildcards, and unions; no general XPath engine.
nillable and xsi:nil	Supported	Nil content and fixed/nillable rules are enforced.
xsi:type	Supported	Runtime QName resolution plus derivation and block checks.
element and attribute defaults/fixed values	Supported	Atomic, list, union, simple-content, anyType, and mixed-complex value constraints.
pattern facet	Supported	Bounded subset with grouping, alternation, repetition, class subtraction, implicit whole-value anchoring, standard name/multi-character escapes, and Unicode categories/blocks. Some accepted W3C expressions are rejected explicitly and are listed as unsupported in the W3C baseline.
DTD and XML entities	Unsupported	Rejected deliberately by schema and embedded XML processing.
event-driven validation	Supported	Bounded expanded-name events, namespace/QName values, recursive content models, substitution, wildcards, dynamic types, and identity constraints. Identity constraints require the optional scratch allocator.
Mini-XML 4 adapter	Supported	Optional adapter selected when Mini-XML is available.
XSD 1.1	Unsupported	zxsd targets XSD 1.0.

Typed bindings

zxsdc --bindings generates C structures with read and write functions for global elements with a complex type. Bindings cover a subset of the constructs above: wildcards, mixed content, xs:anyType, repeating model groups, nillable and abstract elements, substitution-group heads, abstract types, and QName or NOTATION values are rejected with a bindings: diagnostic. They remain fully supported for validation. See Typed bindings.

This matrix is a feature contract, not a claim of complete XSD 1.0 implementation. See Conformance and test coverage for how these claims are tested.