Scenario $1$: Digital Music Store

Acts $($bands or individual performers$)$ perform on music tracks.

Each act may perform more than onetrack.

Even for collaborative works we only keep track of one performer per one piece of music.

Each act in our database has to perform at least one track.

We do not have any tracks by anonymous or unknown acts.

Track belongs to a genre.

Each track belongs to only one genre.

Each genre may have more than one track.

We do not have any tracks that are not defined by a genre.

Each genre in our database has to have at least one track.

Albums have between $4$ and $20$ tracks.

A music track may appear on more than one album but not all tracks have to appear on an album

Acts can have more than one album.

Each album may be made by more than one act.

Not all acts have to have an album.

Albums have to have at least one act.