The language has changed significantly over time. Originally, Factor programs centered on manipulating Java objects with Java's reflection capabilities. From the beginning, the design philosophy has been to modify the language to suit programs written in it. As the Factor implementation and standard libraries grew more detailed, the need for certain language features became clear, and they were added. JFactor did not have an object system where you could define your own classes, and early versions of native Factor were the same; the language was similar to Scheme in this way. Today, the object system is a central part of Factor. Other important language features such as tuple classes, combinator inlining, macros, user-defined parsing words and the modern vocabulary system were only added in a piecemeal fashion as their utility became clear.