We observe that context-aware systems currently developed in one domain or another are mostly technology-driven, and not so much user-centric. They are often not based on a thorough analysis of the effects they produce when interacting with their context, especially regarding the contribution of these effects to user needs. We argue that a conceptual framework is needed to support such analyses. In this paper we identify the concepts necessary to define important structural aspects of a context-aware system and its context, and to formulate generalizations about effects of the interaction of the context-aware system and its context related to user needs. Using this conceptual framework, we classify context-aware systems in terms of the kinds of context assumptions that we can make at design time, and we discuss several threats to validity of a context-aware system. We believe that the proposed conceptual framework can help to better assess the utility concerning a context-aware system design. We use various examples of context-aware applications to illustrate our ideas.

Drone technology can potentially be useful for land-borer security - unmanned drone missions could be performed in the sky, supported by embedded sensors and data processing. Algorithmic rules can be incorporated in the drone software to make instant decisions, whereas other decisions might be made on the ground on the basis of monitoring data received from the drone. This allows for achieving context-awareness: the operation of the drone depends on the situation at hand. The mix of algorithmic and human decision-making distributed over many components raises questions that concern accountability - who would be responsible in case of an accident or a 'wrong doing': the hardware or software developers, the ground station managers, the law (regulations) makers, or the ones who have decided to use drones in the particular situation? In the current work we analyze the usability of drones with regard to land border security, featuring benefits and corresponding accountability concerns. To achieve this, we have studied drone technology and in particular: the technical features as well as the corresponding actor-roles and relationships, considering a land-border-security-related application scenario. On that basis we have carried out an analysis from an accountability perspective.