The place of metadata
I am entering this picture into the blog mainly so I can refer to it if I need to.
The problem is that people often get confused about these relationships. Maybe I am confused and it’s catching, but I have no evidence of this.
Some people like to talk about “the metadata for a bridge”. That really bothers me. Metadata in common usage (outside of circles of confused informatics weenies) means information about information. Look it up. So what’s really meant is “a description of a bridge” or “data about a bridge”.
Some people like to say that all information resources (document-like things) are descriptions. They aren’t. A symphony isn’t a description, nor is a word list.
The main message is the center axis but the side classes are added to document what another subclass choice would be in each case.
I don’t know much UML but I have picked up one habit, which is to use this kind of arrow (the one whose head looks like a triangle) to mean “is a subclass of” or “is a”. If it were a relation like others you see in diagrams like this where the nodes are classes, the relation would be “equals” where some of the things in the target are not equal to anything in the source. Using a different kind of arrowhead emphasizes the difference in kind. Relation links to me mean “some of these are [label]-related to some of those.” I could use UML or ER detailing (double-arrow and so on) to say whether it’s some or all in each case and whether the relationship is functional or inverse functional, but I don’t because I can never member what those funny annotations mean.
To relate to the FRBR discussion, a BR (bibliographic record) would be one kind of metadata record.