id	author	title	date	pages	extension	mime	words	sentence	flesch	summary	cache	txt
ajis02-144	Vrazalic, Lejla	Evaluating Distributed Usability: the role of user interfaces in an activity system	2003	14	.pdf	application/pdf	8555	395	45	A hierarchical system of contradictions is inherent to activity systems and it is these contradictions that cause an activity to develop over time. Engeström (1987) states that contradictions emerge as a result of conflicts within and between activity systems.	cache/ajis02-144.pdf	txt/ajis02-144.txt