Add model validation

6 files changed, 926 insertions, 4 deletions

diff --git a/NEWS b/NEWS
index d14d3b24..2e416c57 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,7 @@ serd (1.0.1) unstable;
   * Add extensible logging API
   * Add extensible logging API
   * Add model for storing statements in memory
+  * Add support for validation
   * Bring read/write interface closer to C standard
   * Make nodes opaque
   * Make serd_strtod API const-correct
diff --git a/serd/serd.h b/serd/serd.h
index 45b61a4a..6bdb9164 100644
--- a/serd/serd.h
+++ b/serd/serd.h
@@ -109,7 +109,8 @@ typedef enum {
 	SERD_ERR_ID_CLASH,    ///< Encountered clashing blank node IDs
 	SERD_ERR_BAD_CURIE,   ///< Invalid CURIE (e.g. prefix does not exist)
 	SERD_ERR_INTERNAL,    ///< Unexpected internal error (should not happen)
-	SERD_ERR_OVERFLOW     ///< Stack overflow
+	SERD_ERR_OVERFLOW,    ///< Stack overflow
+	SERD_ERR_INVALID      ///< Invalid data
 } SerdStatus;
 
 /// RDF syntax type
@@ -1564,6 +1565,21 @@ SerdStatus
 serd_model_erase_range(SerdModel* model, SerdRange* range);
 
 /**
+   Validate model.
+
+   This performs validation based on the RDFS and OWL vocabularies.  All
+   necessary data, including those vocabularies and any property/class
+   definitions that use them, are assumed to be in `model`.
+
+   Validation errors are reported to the world's error sink.
+
+   @return 0 on success.
+*/
+SERD_API
+SerdStatus
+serd_validate(const SerdModel* model);
+
+/**
    @}
    @name Inserter
    @{
diff --git a/src/string.c b/src/string.c
index a914e869..9f82efb1 100644
--- a/src/string.c
+++ b/src/string.c
@@ -44,6 +44,7 @@ serd_strerror(SerdStatus status)
 	case SERD_ERR_BAD_CURIE:  return "Invalid CURIE";
 	case SERD_ERR_INTERNAL:   return "Internal error";
 	case SERD_ERR_OVERFLOW:   return "Stack overflow";
+	case SERD_ERR_INVALID:    return "Invalid data";
 	}
 	return "Unknown error";  // never reached
 }
diff --git a/src/validate.c b/src/validate.c
new file mode 100644
index 00000000..99e22eaf
--- /dev/null
+++ b/src/validate.c
@@ -0,0 +1,880 @@
+/*
+  Copyright 2012-2019 David Robillard <http://drobilla.net>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include "serd_config.h"
+
+#include "model.h"
+#include "serd/serd.h"
+#include "world.h"
+
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef HAVE_PCRE
+#include <pcre.h>
+#endif
+
+#define NS_owl  "http://www.w3.org/2002/07/owl#"
+#define NS_rdf  "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+#define NS_rdfs "http://www.w3.org/2000/01/rdf-schema#"
+#define NS_xsd  "http://www.w3.org/2001/XMLSchema#"
+
+#define VERRORF(ctx, statement, fmt, ...)                                      \
+	report(ctx, statement, SERD_LOG_LEVEL_ERR, fmt, __VA_ARGS__);
+
+#define VERROR(ctx, statement, fmt)                                            \
+	report(ctx, statement, SERD_LOG_LEVEL_ERR, fmt);
+
+#define VWARNF(ctx, statement, fmt, ...)                                       \
+	report(ctx, statement, SERD_LOG_LEVEL_WARNING, fmt, __VA_ARGS__);
+
+#define VNOTEF(ctx, statement, fmt, ...)                                       \
+	report(ctx, statement, SERD_LOG_LEVEL_NOTICE, fmt, __VA_ARGS__);
+
+#define VNOTE(ctx, statement, fmt)                                             \
+	report(ctx, statement, SERD_LOG_LEVEL_NOTICE, fmt);
+
+#define SERD_FOREACH(name, range)                                              \
+	for (const SerdStatement* (name) = NULL;                                   \
+	     !serd_range_empty(range) && ((name) = serd_range_front(range));       \
+	     serd_range_next(range))
+
+typedef struct
+{
+	SerdNode* owl_Class;
+	SerdNode* owl_DatatypeProperty;
+	SerdNode* owl_FunctionalProperty;
+	SerdNode* owl_InverseFunctionalProperty;
+	SerdNode* owl_ObjectProperty;
+	SerdNode* owl_Restriction;
+	SerdNode* owl_Thing;
+	SerdNode* owl_allValuesFrom;
+	SerdNode* owl_cardinality;
+	SerdNode* owl_equivalentClass;
+	SerdNode* owl_maxCardinality;
+	SerdNode* owl_minCardinality;
+	SerdNode* owl_onDatatype;
+	SerdNode* owl_onProperty;
+	SerdNode* owl_someValuesFrom;
+	SerdNode* owl_withRestrictions;
+	SerdNode* rdf_PlainLiteral;
+	SerdNode* rdf_Property;
+	SerdNode* rdf_first;
+	SerdNode* rdf_rest;
+	SerdNode* rdf_type;
+	SerdNode* rdfs_Class;
+	SerdNode* rdfs_Datatype;
+	SerdNode* rdfs_Literal;
+	SerdNode* rdfs_Resource;
+	SerdNode* rdfs_domain;
+	SerdNode* rdfs_label;
+	SerdNode* rdfs_range;
+	SerdNode* rdfs_subClassOf;
+	SerdNode* xsd_anyURI;
+	SerdNode* xsd_float;
+	SerdNode* xsd_decimal;
+	SerdNode* xsd_double;
+	SerdNode* xsd_maxExclusive;
+	SerdNode* xsd_maxInclusive;
+	SerdNode* xsd_minExclusive;
+	SerdNode* xsd_minInclusive;
+	SerdNode* xsd_pattern;
+	SerdNode* xsd_string;
+	SerdNode* sentinel;
+} URIs;
+
+typedef struct
+{
+	URIs             uris;
+	const SerdModel* model;
+	unsigned         n_errors;
+	unsigned         n_restrictions;
+	bool             quiet;
+} ValidationContext;
+
+static int
+check_class_restriction(ValidationContext*   ctx,
+                        const SerdNode*      restriction,
+                        const SerdStatement* statement,
+                        const SerdNode*      instance);
+
+static int
+report(ValidationContext*   ctx,
+       const SerdStatement* statement,
+       const SerdLogLevel   level,
+       const char*          fmt,
+       ...)
+{
+	if (ctx->quiet) {
+		return 0;
+	}
+
+	va_list args;
+	va_start(args, fmt);
+	serd_world_vlogf_internal(ctx->model->world, SERD_ERR_INVALID,
+	                          level,
+	                          serd_statement_get_cursor(statement),
+	                          fmt,
+	                          args);
+	va_end(args);
+
+	++ctx->n_errors;
+	return 1;
+}
+
+static bool
+check(ValidationContext* ctx, const bool value)
+{
+	++ctx->n_restrictions;
+	return value;
+}
+
+/** Return true iff `child` is a descendant of `parent` by `pred` arcs.
+ *
+ * That is, returns true if there is a path from `child` to `parent` by
+ * following `pred` arcs starting from child.
+ */
+static bool
+is_descendant(ValidationContext* ctx,
+              const SerdNode*    child,
+              const SerdNode*    parent,
+              const SerdNode*    pred)
+{
+	if (serd_node_equals(child, parent) ||
+	    serd_model_ask(
+	        ctx->model, child, ctx->uris.owl_equivalentClass, parent, NULL)) {
+		return true;
+	}
+
+	SerdRange* i = serd_model_range(ctx->model, child, pred, NULL, NULL);
+	SERD_FOREACH (s, i) {
+		const SerdNode* o = serd_statement_get_object(s);
+		if (!serd_node_equals(child, o) &&
+		    is_descendant(ctx, o, parent, pred)) {
+			serd_range_free(i);
+			return true;
+		}
+	}
+	serd_range_free(i);
+
+	return false;
+}
+
+/** Return true iff `child` is a subclass of `parent`. */
+static bool
+is_subclass(ValidationContext* ctx,
+            const SerdNode*    child,
+            const SerdNode*    parent)
+{
+	return is_descendant(ctx, child, parent, ctx->uris.rdfs_subClassOf);
+}
+
+/** Return true iff `child` is a sub-datatype of `parent`. */
+static bool
+is_subdatatype(ValidationContext* ctx,
+               const SerdNode*    child,
+               const SerdNode*    parent)
+{
+	return is_descendant(ctx, child, parent, ctx->uris.owl_onDatatype);
+}
+
+static bool
+regexp_match(ValidationContext*   ctx,
+             const SerdStatement* pat_statement,
+             const char*          pat,
+             const char*          str)
+{
+#ifdef HAVE_PCRE
+	// Append a $ to the pattern so we only match if the entire string matches
+	const size_t len  = strlen(pat);
+	char* const  regx = (char*)malloc(len + 2);
+	memcpy(regx, pat, len);
+	regx[len]     = '$';
+	regx[len + 1] = '\0';
+
+	const char* err;
+	int         erroffset;
+	pcre*       re = pcre_compile(regx, PCRE_ANCHORED, &err, &erroffset, NULL);
+	free(regx);
+	if (!re) {
+		VERRORF(ctx,
+		        pat_statement,
+		        "Error in pattern \"%s\" at offset %d (%s)\n",
+		        pat,
+		        erroffset,
+		        err);
+		return false;
+	}
+
+	const bool ret =
+		pcre_exec(re, NULL, str, (int)strlen(str), 0, 0, NULL, 0) >= 0;
+
+	pcre_free(re);
+	return ret;
+#else
+	(void)ctx;
+	(void)pat_statement;
+	(void)pat;
+	(void)str;
+#endif // HAVE_PCRE
+	return true;
+}
+
+static int
+bound_cmp(ValidationContext* ctx,
+          const SerdNode*    literal,
+          const SerdNode*    type,
+          const SerdNode*    bound)
+{
+	const char* str       = serd_node_get_string(literal);
+	const char* bound_str = serd_node_get_string(bound);
+	const bool is_numeric = (is_subdatatype(ctx, type, ctx->uris.xsd_decimal) ||
+	                         is_subdatatype(ctx, type, ctx->uris.xsd_double));
+
+	if (is_numeric) {
+		const double fbound   = serd_strtod(bound_str, NULL);
+		const double fliteral = serd_strtod(str, NULL);
+		return ((fliteral < fbound) ? -1 : (fliteral > fbound) ? 1 : 0);
+	} else {
+		return strcmp(str, bound_str);
+	}
+}
+
+static bool
+check_literal_restriction(ValidationContext*   ctx,
+                          const SerdStatement* statement,
+                          const SerdNode*      literal,
+                          const SerdNode*      type,
+                          const SerdNode*      restriction)
+{
+	const char* str = serd_node_get_string(literal);
+
+	// Check xsd:pattern
+	const SerdStatement* pat_statement = serd_model_get_statement(
+	    ctx->model, restriction, ctx->uris.xsd_pattern, 0, 0);
+	if (pat_statement) {
+		const SerdNode* pat_node = serd_statement_get_object(pat_statement);
+		const char*     pat      = serd_node_get_string(pat_node);
+		if (check(ctx, !regexp_match(ctx, pat_statement, pat, str))) {
+			VERRORF(ctx,
+			        statement,
+			        "Value \"%s\" does not match pattern \"%s\"\n",
+			        serd_node_get_string(literal),
+			        pat);
+			return false;
+		}
+	}
+
+	// Check xsd:minInclusive
+	const SerdNode* lower = serd_model_get(
+	    ctx->model, restriction, ctx->uris.xsd_minInclusive, 0, 0);
+	if (lower) {
+		if (check(ctx, bound_cmp(ctx, literal, type, lower) < 0)) {
+			VERRORF(ctx,
+			        statement,
+			        "Value \"%s\" < minimum \"%s\"\n",
+			        serd_node_get_string(literal),
+			        serd_node_get_string(lower));
+			return false;
+		}
+	}
+
+	// Check xsd:maxInclusive
+	const SerdNode* upper = serd_model_get(
+	    ctx->model, restriction, ctx->uris.xsd_maxInclusive, 0, 0);
+	if (upper) {
+		if (check(ctx, bound_cmp(ctx, literal, type, upper) > 0)) {
+			VERRORF(ctx,
+			        statement,
+			        "Value \"%s\" > than maximum \"%s\"\n",
+			        serd_node_get_string(literal),
+			        serd_node_get_string(upper));
+			return false;
+		}
+	}
+
+	// Check xsd:minExclusive
+	const SerdNode* elower = serd_model_get(
+	    ctx->model, restriction, ctx->uris.xsd_minExclusive, 0, 0);
+	if (elower) {
+		if (check(ctx, bound_cmp(ctx, literal, type, elower) <= 0)) {
+			VERRORF(ctx,
+			        statement,
+			        "Value \"%s\" <= exclusive minimum \"%s\"\n",
+			        serd_node_get_string(literal),
+			        serd_node_get_string(elower));
+			return false;
+		}
+	}
+
+	// Check xsd:maxExclusive
+	const SerdNode* eupper = serd_model_get(
+	    ctx->model, restriction, ctx->uris.xsd_maxExclusive, 0, 0);
+	if (eupper) {
+		if (check(ctx, bound_cmp(ctx, literal, type, eupper) >= 0)) {
+			VERRORF(ctx,
+			        statement,
+			        "Value \"%s\" >= exclusive maximum \"%s\"\n",
+			        serd_node_get_string(literal),
+			        serd_node_get_string(eupper));
+			return false;
+		}
+		++ctx->n_restrictions;
+	}
+
+	return true; // Unknown restriction, be quietly tolerant
+}
+
+static bool
+is_datatype(ValidationContext* ctx, const SerdNode* dtype)
+{
+	SerdRange* t =
+	    serd_model_range(ctx->model, dtype, ctx->uris.rdf_type, NULL, NULL);
+	SERD_FOREACH (s, t) {
+		const SerdNode* type = serd_statement_get_object(s);
+		if (is_subdatatype(ctx, type, ctx->uris.rdfs_Datatype)) {
+			serd_range_free(t);
+			return true; // Subdatatype of rdfs:Datatype
+		}
+	}
+	serd_range_free(t);
+
+	return false;
+}
+
+static bool
+literal_is_valid(ValidationContext*   ctx,
+                 const SerdStatement* statement,
+                 const SerdNode*      literal,
+                 const SerdNode*      type)
+{
+	if (!type) {
+		return true;
+	}
+
+	// Check that datatype is defined
+	const SerdNode* datatype = serd_node_get_datatype(literal);
+	if (datatype && !is_datatype(ctx, datatype)) {
+		VERRORF(ctx,
+		        statement,
+		        "Datatype <%s> is not defined\n",
+		        serd_node_get_string(datatype));
+		return false;
+	}
+
+	// Find restrictions list
+	const SerdNode* head =
+	    serd_model_get(ctx->model, type, ctx->uris.owl_withRestrictions, 0, 0);
+
+	// Walk list, checking each restriction
+	while (head) {
+		SerdIter* f =
+		    serd_model_find(ctx->model, head, ctx->uris.rdf_first, 0, 0);
+		if (!f) {
+			break;
+		}
+
+		const SerdNode* first = serd_statement_get_object(serd_iter_get(f));
+
+		// Check this restriction
+		if (!check_literal_restriction(ctx, statement, literal, type, first)) {
+			VNOTEF(ctx,
+			       serd_iter_get(f),
+			       "Restriction on <%s>\n",
+			       serd_node_get_string(type));
+			serd_iter_free(f);
+			return false;
+		}
+
+		// Seek to next list node
+		head = serd_model_get(ctx->model, head, ctx->uris.rdf_rest, 0, 0);
+		serd_iter_free(f);
+	}
+
+	// Recurse up datatype hierarchy
+	const SerdNode* super =
+	    serd_model_get(ctx->model, type, ctx->uris.owl_onDatatype, 0, 0);
+	return super ? literal_is_valid(ctx, statement, literal, super) : true;
+}
+
+static bool
+is_a(ValidationContext* ctx, const SerdNode* subject, const SerdNode* type)
+{
+	return serd_model_ask(ctx->model, subject, ctx->uris.rdf_type, type, 0);
+}
+
+static bool
+has_explicit_type(ValidationContext* ctx,
+                  const SerdNode*    node,
+                  const SerdNode*    klass)
+{
+	if (is_a(ctx, node, klass)) {
+		return true; // Directly stated to be an instance
+	}
+
+	SerdRange* t =
+	    serd_model_range(ctx->model, node, ctx->uris.rdf_type, NULL, NULL);
+	SERD_FOREACH (s, t) {
+		if (is_subclass(ctx, serd_statement_get_object(s), klass)) {
+			serd_range_free(t);
+			return true; // Explicit instance of a subclass
+		}
+	}
+
+	serd_range_free(t);
+	return false;
+}
+
+static bool
+is_instance_of(ValidationContext* ctx,
+               const SerdNode*    node,
+               const SerdNode*    klass)
+{
+	if (!serd_model_ask(ctx->model, node, NULL, NULL, NULL)) {
+		/* Nothing about this node known in the model at all, assume it is some
+		   external resource we can't validate. */
+		return true;
+	} else if (serd_node_get_type(node) == SERD_BLANK) {
+		/* Be permissive for blank nodes and don't require explicit type
+		   annotation, to avoid countless errors with things like lists. */
+		return true;
+	}
+
+	return (has_explicit_type(ctx, node, klass) ||
+	        serd_node_equals(klass, ctx->uris.rdfs_Resource) ||
+	        serd_node_equals(klass, ctx->uris.owl_Thing));
+}
+
+static bool
+check_instance_type(ValidationContext*   ctx,
+                    const SerdStatement* statement,
+                    const SerdNode*      node,
+                    const SerdNode*      klass)
+{
+	if (is_subclass(ctx, klass, ctx->uris.rdfs_Literal) ||
+	    is_a(ctx, klass, ctx->uris.rdfs_Datatype)) {
+		VERROR(ctx, statement, "Class instance found where literal expected\n");
+		return false;
+	}
+
+	if (is_a(ctx, klass, ctx->uris.owl_Restriction)) {
+		if (check_class_restriction(ctx, klass, statement, node)) {
+			return false;
+		}
+	}
+
+	SerdRange* r = serd_model_range(
+		ctx->model, klass, ctx->uris.rdfs_subClassOf, NULL, NULL);
+	SERD_FOREACH (s, r) {
+		const SerdNode* super = serd_statement_get_object(s);
+		if (!serd_node_equals(super, klass) &&
+		    !check_instance_type(ctx, statement, node, super)) {
+			serd_range_free(r);
+			return false;
+		}
+	}
+	serd_range_free(r);
+
+	if (!is_instance_of(ctx, node, klass)) {
+		VERRORF(ctx,
+		        statement,
+		        "Node %s is not an instance of %s\n",
+		        serd_node_get_string(node),
+		        serd_node_get_string(klass));
+		return false;
+	}
+
+	return true;
+}
+
+static bool
+check_type(ValidationContext*   ctx,
+           const SerdStatement* statement,
+           const SerdNode*      node,
+           const SerdNode*      type)
+{
+	if (serd_node_equals(type, ctx->uris.rdfs_Resource) ||
+	    serd_node_equals(type, ctx->uris.owl_Thing)) {
+		return true; // Trivially true for everything (more or less)
+	}
+
+	if (serd_node_get_type(node) == SERD_LITERAL) {
+		if (serd_node_equals(type, ctx->uris.rdfs_Literal)) {
+			return true; // Trivially true for a literal
+		} else if (serd_node_equals(type, ctx->uris.rdf_PlainLiteral)) {
+			if (serd_node_get_datatype(node)) {
+				VERRORF(ctx,
+				        statement,
+				        "Literal \"%s\" should be plain, but has datatype "
+				        "<%s>\n",
+				        serd_node_get_string(node),
+				        serd_node_get_string(serd_node_get_datatype(node)));
+				return false;
+			}
+		} else if (!is_a(ctx, type, ctx->uris.rdfs_Datatype)) {
+			VERRORF(ctx,
+			        statement,
+			        "Literal \"%s\" where instance of <%s> expected\n",
+			        serd_node_get_string(node),
+			        serd_node_get_string(type));
+			return false;
+		} else {
+			return literal_is_valid(ctx, statement, node, type);
+		}
+	} else if (serd_node_get_type(node) == SERD_URI) {
+		if (!is_subdatatype(ctx, type, ctx->uris.xsd_anyURI)) {
+			// Only check if type is not anyURI, since node is a URI
+			return check_instance_type(ctx, statement, node, type);
+		}
+	} else {
+		return check_instance_type(ctx, statement, node, type);
+	}
+
+	return true;
+}
+
+static uint64_t
+count_non_blanks(SerdRange* i, SerdField field)
+{
+	uint64_t n = 0;
+	SERD_FOREACH (s, i) {
+		const SerdNode* node = serd_statement_get_node(s, field);
+		if (serd_node_get_type(node) != SERD_BLANK) {
+			++n;
+		}
+	}
+	return n;
+}
+
+static int
+check_statement(ValidationContext* ctx, const SerdStatement* statement)
+{
+	int             st   = 0;
+	const URIs*     uris = &ctx->uris;
+	const SerdNode* subj = serd_statement_get_subject(statement);
+	const SerdNode* pred = serd_statement_get_predicate(statement);
+	const SerdNode* obj  = serd_statement_get_object(statement);
+
+	if (serd_node_equals(pred, uris->rdf_type)) {
+		// Type statement, check that object is a valid instance of type
+		check_type(ctx, statement, subj, obj);
+	}
+
+	if (!serd_model_ask(ctx->model, pred, uris->rdfs_label, 0, 0)) {
+		// Warn if property has no label
+		st = VWARNF(ctx,
+		            statement,
+		            "Property <%s> has no label\n",
+		            serd_node_get_string(pred));
+	}
+
+	if (serd_node_get_type(obj) == SERD_LITERAL &&
+	    !literal_is_valid(ctx, statement, obj, serd_node_get_datatype(obj))) {
+		st = SERD_ERR_INVALID;
+	}
+
+	// Check restrictions based on property type
+	if (is_a(ctx, pred, uris->owl_DatatypeProperty)) {
+		if (serd_node_get_type(obj) != SERD_LITERAL) {
+			st = VERROR(ctx, statement,
+			            "Datatype property with non-literal value\n");
+		}
+	} else if (is_a(ctx, pred, uris->owl_ObjectProperty)) {
+		if (serd_node_get_type(obj) == SERD_LITERAL) {
+			st = VERROR(ctx, statement, "Object property with literal value\n");
+		}
+	} else if (is_a(ctx, pred, uris->owl_FunctionalProperty)) {
+		SerdRange*     o = serd_model_range(ctx->model, subj, pred, NULL, NULL);
+		const uint64_t n = count_non_blanks(o, SERD_OBJECT);
+		if (n > 1) {
+			st = VERRORF(ctx, statement,
+			             "Functional property with %u objects\n", n);
+		}
+		serd_range_free(o);
+	} else if (is_a(ctx, pred, uris->owl_InverseFunctionalProperty)) {
+		SerdRange*     s = serd_model_range(ctx->model, NULL, pred, obj, NULL);
+		const uint64_t n = count_non_blanks(s, SERD_SUBJECT);
+		if (n > 1) {
+			st = VERRORF(ctx, statement,
+			             "Inverse functional property with %u subjects\n", n);
+		}
+		serd_range_free(s);
+	} else {
+		SerdRange* t = serd_model_range(ctx->model, pred, uris->rdf_type, 0, 0);
+
+		bool is_property = false;
+		SERD_FOREACH (s, t) {
+			const SerdNode* type = serd_statement_get_object(s);
+			if (is_subclass(ctx, type, uris->rdf_Property)) {
+				is_property = true;
+				break;
+			}
+		}
+
+		if (!is_property) {
+			st = VERROR(ctx, statement, "Use of undefined property\n");
+		}
+
+		serd_range_free(t);
+	}
+
+	// Check range
+	SerdRange* r = serd_model_range(ctx->model, pred, uris->rdfs_range, 0, 0);
+	SERD_FOREACH (s, r) {
+		const SerdNode* range = serd_statement_get_object(s);
+		if (!has_explicit_type(ctx, obj, range) &&
+		    !check_type(ctx, statement, obj, range)) {
+			VNOTEF(ctx, serd_range_front(r),
+			       "In range of <%s>\n", serd_node_get_string(pred));
+		}
+	}
+	serd_range_free(r);
+
+	// Check domain
+	SerdRange* d = serd_model_range(ctx->model, pred, uris->rdfs_domain, 0, 0);
+	SERD_FOREACH (s, d) {
+		const SerdNode* domain = serd_statement_get_object(s);
+		if (!has_explicit_type(ctx, subj, domain) &&
+		    !check_type(ctx, statement, subj, domain)) {
+			VNOTEF(ctx, serd_range_front(d),
+			       "In domain of <%s>\n", serd_node_get_string(pred));
+		}
+	}
+	serd_range_free(d);
+
+	return st;
+}
+
+static int
+cardinality_error(ValidationContext*   ctx,
+                  const SerdStatement* statement,
+                  const SerdStatement* restriction_statement,
+                  const SerdNode*      property,
+                  const size_t         actual_values,
+                  const char*          comparison,
+                  const size_t         expected_values)
+{
+	const int st = VERRORF(ctx,
+	                       statement,
+	                       "Property <%s> has %zu %s %zu values\n",
+	                       serd_node_get_string(property),
+	                       actual_values,
+	                       comparison,
+	                       expected_values);
+	VNOTE(ctx, restriction_statement, "Restriction here\n");
+	return st;
+}
+
+static int
+check_property_restriction(ValidationContext*   ctx,
+                           const SerdNode*      restriction,
+                           const SerdNode*      prop,
+                           const SerdStatement* statement,
+                           const SerdNode*      instance)
+{
+	typedef size_t Count;
+
+	int          st = 0;
+	const size_t values =
+		serd_model_count(ctx->model, instance, prop, NULL, NULL);
+
+	// Check exact cardinality
+	const SerdStatement* c = serd_model_get_statement(
+	    ctx->model, restriction, ctx->uris.owl_cardinality, NULL, NULL);
+	if (c) {
+		const SerdNode* card  = serd_statement_get_object(c);
+		const Count     count = strtoul(serd_node_get_string(card), NULL, 10);
+		if (check(ctx, values != count)) {
+			st = cardinality_error(
+				ctx, statement, c, prop, values, "!=", count);
+		}
+	}
+
+	// Check minimum cardinality
+	const SerdStatement* l = serd_model_get_statement(
+	    ctx->model, restriction, ctx->uris.owl_minCardinality, NULL, NULL);
+	if (l) {
+		const SerdNode* card  = serd_statement_get_object(l);
+		const Count     count = strtoul(serd_node_get_string(card), NULL, 10);
+		if (check(ctx, values < count)) {
+			st = cardinality_error(ctx, statement, l, prop, values, "<", count);
+		}
+	}
+
+	// Check maximum cardinality
+	const SerdStatement* u = serd_model_get_statement(
+	    ctx->model, restriction, ctx->uris.owl_maxCardinality, NULL, NULL);
+	if (u) {
+		const SerdNode* card  = serd_statement_get_object(u);
+		const Count     count = strtoul(serd_node_get_string(card), NULL, 10);
+		if (check(ctx, values > count)) {
+			st = cardinality_error(ctx, statement, u, prop, values, ">", count);
+		}
+	}
+
+	// Check someValuesFrom
+	const SerdStatement* s = serd_model_get_statement(
+	    ctx->model, restriction, ctx->uris.owl_someValuesFrom, 0, 0);
+	if (s) {
+		const SerdNode* some = serd_statement_get_object(s);
+
+		ctx->quiet = true;
+		SerdRange* v = serd_model_range(ctx->model, instance, prop, NULL, NULL);
+		bool       found = false;
+		SERD_FOREACH (i, v) {
+			const SerdNode* value = serd_statement_get_object(i);
+			if (check_type(ctx, statement, value, some)) {
+				found = true;
+				break;
+			}
+		}
+		ctx->quiet = false;
+
+		if (check(ctx, !found)) {
+			st = VERRORF(ctx,
+			             statement,
+			             "%s has no <%s> values of type <%s>\n",
+			             serd_node_get_string(instance),
+			             serd_node_get_string(prop),
+			             serd_node_get_string(some));
+			VNOTE(ctx, s, "Restriction here\n");
+		}
+		serd_range_free(v);
+	}
+
+	// Check allValuesFrom
+	const SerdStatement* a = serd_model_get_statement(
+	    ctx->model, restriction, ctx->uris.owl_allValuesFrom, 0, 0);
+	if (a) {
+		++ctx->n_restrictions;
+		const SerdNode* all = serd_statement_get_object(a);
+
+		SerdRange* v = serd_model_range(ctx->model, instance, prop, NULL, NULL);
+		SERD_FOREACH (i, v) {
+			const SerdNode* value = serd_statement_get_object(i);
+			if (!check_type(ctx, statement, value, all)) {
+				st = VERRORF(ctx,
+				             i,
+				             "<%s> value not of type <%s>\n",
+				             serd_node_get_string(prop),
+				             serd_node_get_string(all));
+				VNOTE(ctx, a, "Restriction here\n");
+				break;
+			}
+		}
+		serd_range_free(v);
+	}
+
+	return st;
+}
+
+static int
+check_class_restriction(ValidationContext*   ctx,
+                        const SerdNode*      restriction,
+                        const SerdStatement* statement,
+                        const SerdNode*      instance)
+{
+	const SerdNode* prop = serd_model_get(
+	    ctx->model, restriction, ctx->uris.owl_onProperty, NULL, NULL);
+
+	return prop ? check_property_restriction(
+	                      ctx, restriction, prop, statement, instance)
+	            : 0;
+}
+
+static void
+init_uris(URIs* uris)
+{
+#define URI(prefix, suffix)                                                    \
+	uris->prefix##_##suffix = serd_new_uri(NS_##prefix #suffix)
+
+	URI(owl, Class);
+	URI(owl, DatatypeProperty);
+	URI(owl, FunctionalProperty);
+	URI(owl, InverseFunctionalProperty);
+	URI(owl, ObjectProperty);
+	URI(owl, Restriction);
+	URI(owl, Thing);
+	URI(owl, allValuesFrom);
+	URI(owl, cardinality);
+	URI(owl, equivalentClass);
+	URI(owl, maxCardinality);
+	URI(owl, minCardinality);
+	URI(owl, onDatatype);
+	URI(owl, onProperty);
+	URI(owl, someValuesFrom);
+	URI(owl, withRestrictions);
+	URI(rdf, PlainLiteral);
+	URI(rdf, Property);
+	URI(rdf, first);
+	URI(rdf, rest);
+	URI(rdf, type);
+	URI(rdfs, Class);
+	URI(rdfs, Datatype);
+	URI(rdfs, Literal);
+	URI(rdfs, Resource);
+	URI(rdfs, domain);
+	URI(rdfs, label);
+	URI(rdfs, range);
+	URI(rdfs, subClassOf);
+	URI(xsd, anyURI);
+	URI(xsd, float);
+	URI(xsd, decimal);
+	URI(xsd, double);
+	URI(xsd, maxExclusive);
+	URI(xsd, maxInclusive);
+	URI(xsd, minExclusive);
+	URI(xsd, minInclusive);
+	URI(xsd, pattern);
+	URI(xsd, string);
+}
+
+SerdStatus
+serd_validate(const SerdModel* model)
+{
+	ValidationContext ctx;
+	memset(&ctx, 0, sizeof(ValidationContext));
+	init_uris(&ctx.uris);
+
+	ctx.model          = model;
+	ctx.n_errors       = 0;
+	ctx.n_restrictions = 0;
+
+#ifndef HAVE_PCRE
+	fprintf(stderr, "warning: Built without PCRE, datatypes not checked.\n");
+#endif
+
+	int        st = 0;
+	SerdRange* i  = serd_model_all(ctx.model);
+	SERD_FOREACH (statement, i) {
+		st = check_statement(&ctx, statement) || st;
+	}
+	serd_range_free(i);
+
+	printf("Found %d errors (checked %d restrictions)\n",
+	       ctx.n_errors,
+	       ctx.n_restrictions);
+
+	for (SerdNode** n = (SerdNode**)&ctx.uris; *n; ++n) {
+		serd_node_free(*n);
+	}
+
+	return !st && ctx.n_errors == 0 ? SERD_SUCCESS : SERD_ERR_INVALID;
+}
diff --git a/tests/serd_test.c b/tests/serd_test.c
index 80e5b926..041cd9ea 100644
--- a/tests/serd_test.c
+++ b/tests/serd_test.c
@@ -318,7 +318,7 @@ test_strerror(void)
 {
 	const char* msg = NULL;
 	assert(!strcmp((msg = serd_strerror(SERD_SUCCESS)), "Success"));
-	for (int i = SERD_FAILURE; i <= SERD_ERR_OVERFLOW; ++i) {
+	for (int i = SERD_FAILURE; i <= SERD_ERR_INVALID; ++i) {
 		msg = serd_strerror((SerdStatus)i);
 		assert(strcmp(msg, "Success"));
 	}
diff --git a/wscript b/wscript
index ae4fe61b..c2d602db 100644
--- a/wscript
+++ b/wscript
@@ -37,6 +37,7 @@ def options(ctx):
          'no-shared':    'do not build shared library',
          'static-progs': 'build programs as static binaries',
          'largefile':    'build with large file support on 32-bit systems',
+         'no-pcre':      'do not use PCRE, even if present',
          'no-posix':     'do not use POSIX functions, even if present'})
 
 def configure(conf):
@@ -69,6 +70,21 @@ def configure(conf):
                                 defines     = ['_POSIX_C_SOURCE=200809L'],
                                 mandatory   = False)
 
+    if not Options.options.no_pcre:
+        autowaf.check_pkg(conf, 'libpcre', uselib_store='PCRE', mandatory=False)
+
+    if conf.env.HAVE_PCRE:
+        if conf.check(cflags=['-pthread'], mandatory=False):
+            conf.env.PTHREAD_CFLAGS = ['-pthread']
+            if conf.env.CC_NAME != 'clang':
+                conf.env.PTHREAD_LINKFLAGS = ['-pthread']
+        elif conf.check(linkflags=['-lpthread'], mandatory=False):
+            conf.env.PTHREAD_CFLAGS    = []
+            conf.env.PTHREAD_LINKFLAGS = ['-lpthread']
+        else:
+            conf.env.PTHREAD_CFLAGS    = []
+            conf.env.PTHREAD_LINKFLAGS = []
+
     autowaf.set_lib_env(conf, 'serd', SERD_VERSION)
     conf.write_config_header('serd_config.h', remove=False)
 
@@ -100,6 +116,7 @@ lib_source = ['src/base64.c',
               'src/syntax.c',
               'src/system.c',
               'src/uri.c',
+              'src/validate.c',
               'src/world.c',
               'src/writer.c',
               'src/zix/btree.c',
@@ -120,6 +137,7 @@ def build(bld):
                 'includes':        ['.', './src'],
                 'cflags':          ['-fvisibility=hidden'],
                 'lib':             ['m'],
+                'use':             ['PCRE'],
                 'vnum':            SERD_VERSION,
                 'install_path':    '${LIBDIR}'}
     if bld.env.MSVC_COMPILER:
@@ -133,6 +151,7 @@ def build(bld):
             source          = lib_source,
             name            = 'libserd',
             target          = 'serd-%s' % SERD_MAJOR_VERSION,
+            uselib          = 'PCRE',
             defines         = defines + ['SERD_SHARED', 'SERD_INTERNAL'],
             **lib_args)
 
@@ -142,6 +161,7 @@ def build(bld):
             source          = lib_source,
             name            = 'libserd_static',
             target          = 'serd-%s' % SERD_MAJOR_VERSION,
+            uselib          = 'PCRE',
             defines         = defines + ['SERD_INTERNAL'],
             **lib_args)
 
@@ -157,6 +177,7 @@ def build(bld):
             source       = lib_source,
             name         = 'libserd_profiled',
             target       = 'serd_profiled',
+            uselib       = 'PCRE',
             defines      = defines + ['SERD_INTERNAL'],
             **test_args)
 
@@ -185,13 +206,16 @@ def build(bld):
                   target       = 'serdi',
                   includes     = ['.', './src'],
                   use          = 'libserd',
+                  uselib       = 'PCRE',
                   lib          = lib_args['lib'],
+                  cflags       = bld.env.PTHREAD_CFLAGS,
+                  linkflags    = bld.env.PTHREAD_LINKFLAGS,
                   install_path = '${BINDIR}')
         if not bld.env.BUILD_SHARED or bld.env.STATIC_PROGS:
             obj.use = 'libserd_static'
         if bld.env.STATIC_PROGS:
-            obj.env.SHLIB_MARKER = obj.env.STLIB_MARKER
-            obj.linkflags        = ['-static']
+            obj.env.SHLIB_MARKER  = obj.env.STLIB_MARKER
+            obj.linkflags        += ['-static']
 
     # Documentation
     if bld.env.DOCS: