Perplexity breakdown of your reply. (objective is a wiki article)
The “update the namespace” caveat Nick mentioned refers to the importance of ensuring that the XML document’s declared namespace matches the namespace declared in the schema (such as the RelaxNG schema file) used for validation.
Namespaces in XML serve as unique identifiers to distinguish elements and attributes that may have the same name but different meanings across vocabularies. When validating an XML file against a schema, the validator checks that elements and attributes correctly belong to the namespace defined in the schema.
If the XML document uses an outdated or incorrect namespace prefix or URI that does not correspond exactly to the one expected by the schema, validation will fail even if the XML elements structurally conform to the schema’s rules. Thus, updating the namespace in the XML to align it with the schema’s target namespace is essential for successful validation.
In the case of the Gramps example, even if the schema version 1.7.1 is updated, the XML instance document must also have its namespace declarations updated accordingly. Without this, xmllint or any validator will report errors, as the elements in the XML are not recognized as belonging to the schema’s namespace “space” and thus appear invalid.
In summary:
- XML namespaces act like “addresses” for elements/attributes.
- Validation requires the XML instance’s namespaces to match the schema’s namespaces.
- Updating namespaces in the XML to reflect changes in the schema namespace URI or prefix is necessary when schemas evolve.
- Ignoring this step results in validation failure despite correct structural conformity.
- This ensures that both schema and instance document share a common “language” for element names, enabling meaningful validation.
The parameters in the command xmllint --noout --relaxng grampsxml.rng example.gramps mean the following:
--noout: This option tells xmllint not to output the XML content to the standard output after parsing or validation. It suppresses printing the XML document itself and only reports validation errors or messages.--relaxng grampsxml.rng: This specifies that xmllint should validate the XML file against a Relax NG schema instead of a DTD or XML Schema. The grampsxml.rng is the path to the Relax NG schema file used for validation. --relaxng instructs xmllint which schema file to use.example.gramps: This is the input XML file to be parsed and validated. xmllint reads this file to check its conformance with the schema specified via --relaxng.
In summary, the command runs the xmllint XML tool to validate the XML file example.gramps against the Relax NG schema in grampsxml.rng and only outputs validation errors, suppressing the full XML output.
xmllint DTD validation alternative to the Relax NG schema
Nick notes that this currently gives errors even if the namespace is updated.
To validate an XML file against a DTD using xmllint (instead of a Relax NG schema), you would typically use the --valid or --dtdvalid options.
Given the XML snippet specifying the DTD in the DOCTYPE declaration:
xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE database PUBLIC "-//Gramps//DTD Gramps XML 1.7.2//EN"
"http://gramps-project.org/xml/1.7.2/grampsxml.dtd">
<database xmlns="http://gramps-project.org/xml/1.7.2/">
<header>...
You can validate it with xmllint as:
bash
xmllint --noout --valid example.gramps
Here:
--valid tells xmllint to validate the XML file against the DTD referenced inside the file itself (in this case, in the DOCTYPE declaration).--noout suppresses output of the XML content, showing only errors or validation messages.example.gramps is the XML file to validate.
If the XML file did not include a DOCTYPE or you want to specify a DTD file explicitly, you can use:
bash
xmllint --noout --dtdvalid grampsxml.dtd example.gramps
Where --dtdvalid grampsxml.dtd points to the external DTD file explicitly for validation.
In summary, to do the equivalent of validating with a Relax NG schema using a DTD, replace:
--relaxng grampsxml.rng with either --valid if DTD is included internally, or--dtdvalid grampsxml.dtd if referencing an external DTD file explicitly.
This will validate example.gramps against the defined DTD and report any non-compliance errors.