X-TEC: TECHNO-DIDACTICAL EXTENSION FOR INSTRUCTION/LEARNING BASED ON COMPUTER - A New Development Model for Educational Software Topics: Designing Learning Activities; Learning Materials Development; Software Tools for E-Learning; Web-Based Education; Web-Based Teaching and Learning Technologies In Proceedings of WEBIST 2006 - Second International Conference on Web Information Systems and Technologies - Volume 2: WEBIST, 325-331, 2006 , Setúbal, Portugal