No matching global declaration for the validation root (cvc-elt.1.a)

The message

libxml2 (Python lxml, PHP, xmllint, this site):

Element 'Q': No matching global declaration available for the validation root.

Java / Xerces:

cvc-elt.1.a: Cannot find the declaration of element 'Q'.

What it means

The root element of the document is not declared as a global element in the schema you validate against — usually because document and schema do not belong together, or their namespaces differ.

Typical causes

• Validating against the wrong schema (another message type or version).
• Namespace mismatch: the root element has xmlns="…" but the schema's targetNamespace is different or missing — or the other way round.
• The schema is a module that only defines types; the root element is declared in another file that imports it.
• A prefix on the root element that is bound to a different URI.

Example

Schema:

<xs:schema targetNamespace="urn:example:v2" …>
  <xs:element name="Document"/>
</xs:schema>

Document:

<Document xmlns="urn:example:v1">…</Document>   <!-- v1 vs v2 -->

How to fix it

Compare the namespace of the root element with the schema's targetNamespace, and load the main schema file (the one that declares the root element). The viewer can detect the schema from xsi:schemaLocation automatically.

Find every occurrence at once

Load your XML file and its schema in the XML Online Viewer: it lists all validation errors with line, path and the surrounding lines, jumps to each one in the tree, and exports the list to Excel to hand to whoever produces the file. The schema is detected from xsi:schemaLocation when the document names it.

Other errors: all XML validation errors explained.

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