Limitations of E-R Model

Before in the assignment for my class (ISYS 464 Enterprise Data Management), my group saw how the asset could be a support contract, software, and hardware, which all have unique characteristics and many similar characteristics.  Each asset is assigned to a user (operator), supported by some IT staff, and purchased (owned) by some manager.  To represent this in traditional ER model, it would have to look like this.

The ER Model cannot distinguish between different types of objects that share qualities, but differ slightly. We decided there must be a better way...