The problem of object-relational mapping occurs when we try to build an application using an object-oriented programming language and using a relational database for data storage. The source of the problem is the theoretical difference between the data representation in object-oriented context and in RDBMS systems. In a nutshell OO systems consider any kind of data as a network or graph of connected object, and on the other hand the database handles the data in tables and represents connections using key columns (the exact, in-depth explanation of the problem will be included in the first part of the thesis). Application developers often use ORM frameworks (or libraries) for enterprise application development.