If structural schema describes a page, alignment schema describes a relationship — specifically, the relationship between what's on your page and an entity that exists independently of your page, in an external knowledge base. A small number of structured data properties do most of this work, and understanding what they're for (without needing to be a developer) clarifies what alignment actually accomplishes.

The "same as" relationship

At its core, alignment schema lets you state, in machine-readable terms: "the entity described on this page is the same entity as the one identified at this external reference." This is the most direct possible connection between your site and an external knowledge base record — it doesn't describe a relationship like "related to" or "mentioned in," it asserts identity: these are the same thing.

The "main subject" relationship

A related but distinct concept identifies what the primary subject of a page actually is — as opposed to everything else the page might mention in passing. A page might reference dozens of related concepts, people, or places, but have one specific entity as its true subject. Structured data can make that distinction explicit, rather than leaving it to be inferred from context.

Why these need to be correct, not just present

It's possible to add this kind of structured data without it pointing anywhere meaningful — a reference to an entity record that doesn't exist, is incorrect, or doesn't actually correspond to your entity. Markup like this needs to be accurate to function as alignment at all; incorrect references don't just fail to help, they can actively create the kind of inconsistency that undermines corroboration elsewhere.

The plain-language version: alignment schema is your website raising its hand and saying, correctly and verifiably, "the thing I'm describing is this specific, externally-defined entity — here's exactly which one." Everything else in entity engineering builds toward making that statement true and accurate.

Where this fits with everything else

Alignment schema is often the last piece implemented, because it depends on the other layers existing first — there needs to be a correct entity record to reference, and ideally a consistent evidence layer corroborating it. Implemented correctly, on top of those foundations, it's the piece that closes the loop and connects your website into the broader entity infrastructure.