The state of digital comic book metadata is a mess. There is not really a standard format if the metadata even exists at all. All digital comic books consist of is a zip or rar with ordered images and potentially some type of file to store metadata. The closest thing to a standard is the Comic Rack format of metadata and even that is not very widespread. There exists a project called comictagger(on github) that attempts to assign metadata in Comic Rack format but it is somewhat unpolished yet provides a solid feature set.

I am planning on making a program to organize comics based on metadata attributes and am frustrated with the lack of consistency in this department. This isn't really a problem because of any developers but I would argue more so due to the organization of comic books themselves. For example, the term volume can have a different meaning based on who is asked or what context is used. The redundancy between issues and trade paperbacks can also lead to confusion and logistical problems. I just wish we already had a widespread schema in place for comic books metadata already.