Joan Angelina Widians
1) Department of Computer Science and Electronics, Faculty of Mathematics and Natural Science, Gadjah Mada University, Yogyakarta 55281, Indonesia. 2) Department of Informatics, Faculty of Engineering, Mulawarman University, Samarinda 75123 , Indonesia.

Retantyo Wardoyo
Department of Computer Science and Electronics, Faculty of Mathematics and Natural Science, Gadjah Mada University, Yogyakarta 55281,
Indonesia

Sri Hartati
Department of Computer Science and Electronics, Faculty of Mathematics and Natural Science, Gadjah Mada University, Yogyakarta 55281,
Indonesia