| Class | TimeoutError | A low-level SQL operation timed out. |
| Class | BadCredentials | Undocumented |
| Class | NoSuchUser | Undocumented |
| Class | MissingDomainPart | Raised when a login is attempted with a username which consists of only |
| Class | DuplicateUser | Undocumented |
| Class | CannotOpenStore | There is a problem such that the store cannot be opened. |
| Class | NoUpgradePathAvailable | No upgrade path is available, so the store cannot be opened. |
| Class | NoCrossStoreReferences | References are not allowed between items within different Stores. |
| Class | SQLError | Axiom internally generated some bad SQL. |
| Class | TableAlreadyExists | Axiom internally created a table at the same time as another database. |
| Class | UnknownItemType | Can't load an item: it's of a type that I don't see anywhere in Python. |
| Class | SQLWarning | Axiom internally generated some CREATE TABLE SQL that ... probably wasn't bad |
| Class | TableCreationConcurrencyError | Woah, this is really bad. If you can get this please tell us how. |
| Class | DuplicateUniqueItem | Found 2 or more of an item which is supposed to be unique. |
| Class | ItemNotFound | Did not find even 1 of an item which was supposed to exist. |
| Class | ItemClassesOnly | An object was passed to a method that wasn't a subclass of Item. |
| Class | ChangeRejected | Raised when an attempt is made to change the database at a time when |
| Class | DependencyError | Raised when an item can't be installed or uninstalled. |
| Class | DeletionDisallowed | Raised when an attempt is made to delete an item that is referred to by |
| Class | DataIntegrityError | Data integrity seems to have been lost. |
| Class | BrokenReference | A reference to a nonexistent item was detected when this should be |