This special issue of TPLP commemorates the 25th edition of the annual conference organized by GULP (Gruppo Ricercatori e Utenti Logic Programming), the Italian group of researchers and users of logic programming. The first event in this series was held at Genoa in 1986, one year after the foundation of the user group, continuing annually ever since. In 1994, the conference joined forces with the Spanish conference PRODE (on Declarative Programming), and in 1996 with the Portuguese APPIA (on Artificial Intelligence). This collaboration continued until 2003. Starting from 2004, the event became known as CILC (Convegno Italiano di Logica Computazionale, Italian Conference on Computational Logic), thereby broadening its topics to general computational logic, while becoming a national Italian event again. Being one of the oldest and largest national events of its kind, over the years the conference has been an important networking opportunity and catalyst for persons with different backgrounds, coming from theory and practice, and from research and industry, for exchanging their visions, achievements, and challenges in logic programming. For a more detailed historical account on GULP and its annual conferences, we refer to Rossi (2010).