Model-driven software product lines (MD-SPLs) are created from domain models which are transformed, merged and composed with reusable core assets, until software products are produced. Model transformation chains (MTCs) must be specified to generate such MD-SPLs. This paper presents a framework for creating platform-independent MD-SPLs; such framework includes a domain specific language (DSL) for platform-independent MTC specification and facilities platform-specific MTC generation of several of the most used model transformation frameworks. The DSL also allows product line architects to compose generation taking the need for model transformation strategy and technology interoperability into account and specifying several types of variability involved in such generation.