Atom 1.0

<feed>

The root element of an Atom document, and the one place the specification names three children as required rather than recommended.

Atom is stricter than RSS in almost every way, and it starts here: a <feed> must carry <id>, <title> and <updated>, and an author at either the feed or the entry level. Unlike RSS there is no version attribute — the namespace URI is the version.

That namespace is also what makes Atom awkward to query. Every element is in it, so an XPath expression written without a prefix bound to http://www.w3.org/2005/Atom matches nothing at all.

Format: Atom 1.0
Namespace: Atom Syndication Format 1.0
Parent: None — this is the document element
How many: Exactly one, as the document element.

What it contains

Cardinality and constraints

Exactly one, as the document element.

Must declare xmlns="http://www.w3.org/2005/Atom". There is no version attribute.
<id>, <title> and <updated> are all required.
An <author> is required on the feed, or on every entry individually.

What our validator does

All three required children are checked, and each missing one is reported as an error citing RFC 4287.

Broken and fixed

Both documents below are well-formed XML — that is the point of this corpus — and both are run through the validator on every test run. The verdicts here are what it returned, not what we expect it to.

broken

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
  <title>Example</title>
  <updated>2026-08-10T09:00:00Z</updated>
  <author><name>Ada Lovelace</name></author>
  <entry>
    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
    <title>Hen lays egg</title>
    <updated>2026-08-10T09:00:00Z</updated>
  </entry>
</feed>

<feed> is missing the required <id>. RFC 4287 requires all three.

fixed

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
  <id>urn:uuid:60a76c80-d399-11d9-b93c-0003939e0af6</id>
  <title>Example</title>
  <updated>2026-08-10T09:00:00Z</updated>
  <link rel="self" href="https://example.com/feed.xml"/>
  <author><name>Ada Lovelace</name></author>
  <entry>
    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
    <title>Hen lays egg</title>
    <updated>2026-08-10T09:00:00Z</updated>
  </entry>
</feed>

No errors. Warnings may remain — a conforming feed can still be missing a self link — but nothing here is wrong.

Where it reaches

Related elements

All 34 elements

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