BlockDefinition

Whether this block may take the greeting slot. Check it here — you cannot work it out from the block itself. Put any other block in the slot and the diagram breaks welcome_block_not_allowed.

The block's semantic name. It is what the block-level operations address a block by.

A diagram node names the same block by its template, and the catalog does not publish the template yet, so a client holding a diagram cannot tell from here which definition describes a node it already has.

Display name.

One entry when the block behaves the same way regardless of its params. More than one when a param changes what the block is: the selector says which.