Guides
Fix the XML problem in front of you
32 practical guides that begin with the symptom, reduce it to a small reproducible document, and end in a validator or reference page where you can prove the fix.
4 guides
XML
- 6 min readUpdated 2026-08-21
How to fix an invalid XML entity reference
Find the unescaped ampersand, distinguish named entities from character references, and repair the value without hiding malformed input.
Work through the fix - 7 min readUpdated 2026-08-21
XML encoding declaration vs actual bytes
Diagnose XML that declares UTF-8 but arrives in another encoding, then repair the bytes, transport metadata, and declaration as one contract.
Work through the fix - 6 min readUpdated 2026-08-21
How to fix a duplicate XML attribute
Find the repeated expanded attribute name, decide which value owns the field, and fix generators that merge attribute collections unsafely.
Work through the fix - 6 min readUpdated 2026-08-21
How to fix CDATA that contains ]]>
Handle the CDATA terminator without truncating content, understand why CDATA cannot nest, and choose normal escaping when input is arbitrary.
Work through the fix
3 guides
Namespaces
- 7 min readUpdated 2026-08-21
XML namespace prefix vs URI
Understand why prefixes are replaceable aliases, why namespace URIs are compared literally, and how expanded names keep documents interoperable.
Work through the fix - 6 min readUpdated 2026-08-21
How to fix an unbound XML namespace prefix
Find the missing namespace declaration, restore it at the narrowest useful scope, and avoid repairs that silently change the vocabulary URI.
Work through the fix - 7 min readUpdated 2026-08-21
Why the default XML namespace does not apply to attributes
Distinguish unprefixed element and attribute names, qualify attributes deliberately, and prevent namespace-aware lookups from returning nothing.
Work through the fix
5 guides
Sitemaps
- 7 min readUpdated 2026-08-21
How to fix “Sitemap could not be read”
A deterministic checklist for separating fetch failures, HTTP problems, malformed XML, namespace mistakes, and invalid sitemap entries.
Work through the fix - 6 min readUpdated 2026-08-21
How to use sitemap lastmod correctly
What <lastmod> should measure, which date forms are valid, when to omit it, and why stamping every URL on every deploy destroys the signal.
Work through the fix - 7 min readUpdated 2026-08-21
How to split a large XML sitemap
Divide a sitemap before it crosses protocol limits, build a sitemap index, and choose boundaries that make failures and Search Console reports useful.
Work through the fix - 8 min readUpdated 2026-08-21
How to add hreflang to an XML sitemap
Build complete alternate-language clusters with xhtml:link, self-references, reciprocal links, and absolute canonical URLs.
Work through the fix - 7 min readUpdated 2026-08-21
How to debug a failing sitemap-index child
Trace one failing child sitemap from index entry through HTTP retrieval and document validation without rebuilding the entire sitemap set.
Work through the fix
5 guides
Feeds
- 6 min readUpdated 2026-08-21
How to fix an RSS pubDate
Write RSS 2.0 publication dates in the expected RFC 822 family, preserve the real instant, and catch values feed readers silently ignore.
Work through the fix - 7 min readUpdated 2026-08-21
Atom feed required elements checklist
Build the smallest conforming Atom feed, satisfy feed and entry requirements, and handle author and content rules without RSS assumptions.
Work through the fix - 7 min readUpdated 2026-08-21
RSS HTML: CDATA or escaped text?
Publish HTML-shaped RSS descriptions without producing child markup, double-escaping entities, or breaking on an unexpected CDATA terminator.
Work through the fix - 7 min readUpdated 2026-08-21
RSS guid vs link: which one identifies an item?
Keep RSS item identity stable, use isPermaLink correctly, and avoid duplicate entries when article URLs or titles change.
Work through the fix - 7 min readUpdated 2026-08-21
Atom rel=self vs rel=alternate
Publish Atom links with explicit relationships so clients can distinguish the feed document from its human-facing site and entry pages.
Work through the fix
4 guides
XPath
- 7 min readUpdated 2026-08-21
Why XPath matches nothing in a default namespace
The XPath 1.0 namespace rule behind an empty //loc result, with the prefix-bound solution and the local-name fallback.
Work through the fix - 6 min readUpdated 2026-08-21
XPath first match vs first match per parent
Why //item[1] can return several nodes while (//item)[1] returns one, and how predicate context changes the result.
Work through the fix - 7 min readUpdated 2026-08-21
XPath local-name() vs namespace prefixes
Choose explicit namespace bindings for precise XPath, and reserve local-name() fallbacks for deliberate namespace-agnostic inspection.
Work through the fix - 8 min readUpdated 2026-08-21
XPath predicates, position(), and parentheses
Predict which node set an XPath predicate filters, distinguish numeric from boolean predicates, and select the first match at the intended scope.
Work through the fix
8 guides
XSD
- 8 min readUpdated 2026-08-21
XSD minOccurs vs nillable
The difference between an absent element and a present element with xsi:nil, with schemas and instance documents for each case.
Work through the fix - 8 min readUpdated 2026-08-21
XSD sequence vs choice
When child order is fixed, when alternatives are exclusive, and how minOccurs and maxOccurs change the meaning of an XSD compositor.
Work through the fix - 8 min readUpdated 2026-08-21
How to validate XML against an XSD
Separate parsing from schema validation, load the complete schema set, and reduce validation errors to the smallest failing instance.
Work through the fix - 7 min readUpdated 2026-08-21
XSD include vs import
Use xs:include for one namespace and xs:import across namespaces, then make schema resolution deterministic in local and deployed environments.
Work through the fix - 8 min readUpdated 2026-08-21
How to fix “Element is not expected” in XSD
Use the expected-element list to find namespace, order, or occurrence mistakes instead of deleting the child the validator names.
Work through the fix - 8 min readUpdated 2026-08-21
How the XSD pattern facet really matches
Write XSD regular-expression facets without assuming anchors or host-language features, account for normalization, and test boundary literals.
Work through the fix - 9 min readUpdated 2026-08-21
XSD targetNamespace and elementFormDefault
Predict which instance elements must be namespace-qualified, separate schema vocabulary from target vocabulary, and fix no-declaration validation failures.
Work through the fix - 8 min readUpdated 2026-08-21
XSD complex type extension vs restriction
Choose type derivation based on whether the accepted instance set grows or narrows, and avoid restrictions that are not valid subsets of their base type.
Work through the fix
3 guides
SOAP
- 8 min readUpdated 2026-08-21
SOAP 1.1 vs SOAP 1.2
Identify the SOAP version from its envelope namespace, align the HTTP media type and action, and avoid mixing incompatible fault structures.
Work through the fix - 8 min readUpdated 2026-08-21
How to debug a SOAP Fault
Read the standard fault fields before application detail, preserve the HTTP response, and reduce a failing SOAP request without losing context.
Work through the fix - 7 min readUpdated 2026-08-21
SOAPAction in SOAP 1.1 vs SOAP 1.2
Put the action value in the correct HTTP location for each SOAP version and debug dispatch failures without changing a valid envelope blindly.
Work through the fix
What makes these guides different
The symptom comes first
Each guide begins with what you can observe: the parser message, the empty result, or the rejected sitemap.
Examples are executable
XML and XSD snippets are parsed during the test run, and XPath claims link to the evaluator that runs them on libxml2.
The answer has a next action
Every guide ends at a validator, tester, or reference entry rather than at a generic conclusion.
Get started
Bring order to the XML your team can't afford to ignore.
Create a free account and get a private workspace to search, validate, diff, and monitor your XML feeds, sitemaps, schemas, and vendor integrations.