Change URI to IRI after finding validation pattern

category.go

@@ -10,7 +10,7 @@ type Category struct {
 	*CommonAttributes
 	Content Content `xml:"content"` // undefinedContent in RFC4287
 	Term    string  `xml:"term,attr"`
-	Scheme  URI     `xml:"scheme,attr,omitempty"`
+	Scheme  IRI     `xml:"scheme,attr,omitempty"`
 	Label   string  `xml:"label,attr,omitempty"`
 }
 
@@ -33,7 +33,7 @@ func (c *Category) Check() error {
 	}
 
 	if c.Scheme != "" {
-		if !isValidURI(c.Scheme) {
+		if !isValidIRI(c.Scheme) {
 			return fmt.Errorf("scheme attribute %v of category not correctly formatted", c.Scheme)
 		}
 	}