It is my pleasure to announce the third regular issue of 2013. In retrospect of the first three months of the year, we have received even more papers submissions and special issue proposals as well as increasing content access. Open access publications and research become increasingly popular. Following our long-lasting policy which supports not only open access but also no fees for authors, we are very proud to offer this service our community for more than 15 years. At this point, I'd like to gratefully thank all institutions and individuals which make this happen, including the consortium members, editorial board members and the authors.

In this issue, I am very honored to present 5 high quality papers on different aspects in computer science. Loïc Colson and Vincent Demange from France discuss in their work investigations on a pedagogical calculus of constructions. In a collaborative work between Tahereh Jafarikhah from Iran and Klaus Weihrauch from Germany focus their paper on the the Riesz representation theorem. Kazuhiro Ogata und Kokichi Futatsugi from Japan introduce the compositionally writing proof scores of invariants in the OTS/CafeOBJ method. Following the three theoretical papers, a method for the computational representation of the learning flow and data flow in collaborative learning is discussed the international research group of Luis Palomino-Ramírez from Mexico, Miguel L. Bote-Lorenzo and Juan I. Asensio-Pérez from Spain, Laurence Vignollet from France, and Yannis A. Dimitriadis from Spain. Finally, in their paper, Antonio Peñalver, José Júan López, Federico Botella and Jose Antonio Gallud from Spain, propose a new schema-based definition of Distributed User Interfaces (DUIs) allowing the specification and defining constraints of the elements to be distributed.

Enjoy reading!

Cordially,

Christian Gütl, Managing Editor
Graz University of Technology, Graz, Austria
Email: cguetl@iicm.edu