what are the differences between RDBMS and OODBMS

It seems for complex applications, OODBMS simplifies the "encoding" a real-world entity, in a similar way that as OOP has actually simplified the thinking process of a programmer. It seems OODBMS is an implementation of the so-called hierarchial database, by using objects, and that was usually referred to as a 2nd type of database. The 1st type being relational, I think. It seems a simple example of RDB and OOBD for a same simple application is a man-hour tracking DB. RDB could have 5 fields: DATE, MAN_NO, PROJECT_CODE, TIME_START, TIME_END while OODB could have 4 major fields: DATE, MAN_NO, PROJECT_CODE, TIME(START,END) For instance it becomes a lot quicker for the programmer to relate that TIME_START and TIME_END are closely related. What do you think?