We would like to welcome you to Valencia, to attend The 4th International Conference on Software Defined Systems (SDS 2017) in Valencia, Spain from May 8 to May 11, 2017. SDS 2017 is becoming one of most well-known international technical conferences in the area of Software Defined Systems. We are much honored to serve this year as the general chairs of this conference. We are also very proud of this year's program which includes an exceptional line-up of workshops and keynote speeches in addition to an outstanding collection of technical papers.