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Atom 1.0

<entry>

One item in an Atom feed, with the same three required children as the feed itself and an author requirement it can inherit.

Every entry needs <id>, <title> and <updated>. It also needs an author, but that one may come from the feed: an entry with no <author> is valid as long as the feed has one, and invalid otherwise. That inheritance rule is the most commonly missed requirement in Atom.

An entry should also carry content or a summary — the specification requires a <summary> in the cases where <content> is absent or is a remote reference, which is a rule almost nobody implements deliberately.

Cardinality and constraints

Any number per <feed>, including none.

  • <id>, <title> and <updated> are all required on every entry.
  • An author is required at the entry level unless the feed supplies one.
  • A feed with no entries is valid, and reports as a warning rather than an error.

What our validator does

Each entry is checked for the three required children by position, and the feed-or-entry author rule is applied across the whole document.

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">
  <id>urn:uuid:60a76c80-d399-11d9-b93c-0003939e0af6</id>
  <title>Example</title>
  <updated>2026-08-10T09:00:00Z</updated>
  <author><name>Ada Lovelace</name></author>
  <entry>
    <title>Hen lays egg</title>
    <updated>2026-08-10T09:00:00Z</updated>
  </entry>
</feed>
entry 1 is missing the required <id>.
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.

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