Google updated the requirements for logo structure data for AMP articles.
This update clarifies how publishers display structured data for your logo so that it still qualifies for rich results.
Logo Structured Data
Google uses structured logo data to display the correct logo in its rich search results and “knowledge panel”.
The important thing is to correctly specify the logo through structured data.
Incorrect encoding of structured logo data may prevent Google from displaying the logo correctly in rich results or knowledge panel.
The logo is a structured data attribute. You can think of attributes as things, and you can think of structured data types as attributes of that attribute.
The two types that are expected are:
The logo is used in the structured data for the following types:
However, this change only affects the structure data of the article structure data type and is more likely to be used with the organization structure data type.
Logo Structured Data Update
The developer page update is actually a clarification. After the upgrade, you can more clearly understand the AMP structure data requirements for the Google logo.
There are two ways to encode structured data for the logo.
The editor can use the image object type to describe the logo.
Publishers can also use the Logo attribute to convey what the logo is.
The Difference Between a Structured Data Property and a Type
The type is the attribute of the property. You can think of attributes as things.
You can think of the type as an attribute of the thing.
For example, a car can be an example of an attribute and the color of a car can be an attribute.
Source: Google Developers