Browsing by Author "Ikkala, Tapio"
Now showing items 1-2 of 2
-
Ikkala, Tapio (2020)This thesis presents a scalable method for identifying anomalous periods of non-activity in short periodic event sequences. The method is tested with real world point-of-sale (POS) data from grocery retail setting. However, the method can be applied also to other problem domains which produce similar sequential data. The proposed method models the underlying event sequence as a non-homogeneous Poisson process with a piecewise constant rate function. The rate function for the piecewise homogeneous Poisson process can be estimated with a change point detection algorithm that minimises a cost function consisting of the negative Poisson log-likelihood and a penalty term that is linear to the number of change points. The resulting model can be queried for anomalously long periods of time with no events, i.e., waiting times, by defining a threshold below which the waiting time observations are deemed anomalies. The first experimental part of the thesis focuses on model selection, i.e., in finding a penalty value that results in the change point detection algorithm detecting the true changes in the intensity of the arrivals of the events while not reacting to random fluctuations in the data. In the second experimental part the performance of the anomaly detection methodology is measured against stock-out data, which gives an approximate ground truth for the termination of a POS event sequence. The performance of the anomaly detector is found to be subpar in terms of precision and recall, i.e., the true positive rate and the positive predictive value. The number of false positives remains high even with small threshold values. This needs to be taken into account when considering applying the anomaly detection procedure in practice. Nevertheless, the methodology may have practical value in the retail setting, e.g., in guiding the store personnel where to focus their resources in ensuring the availability of the products.
-
Ikkala, Tapio (2014)The widespread diffusion and utilization of ICTs affords new forms of interaction and exchange to emerge between people on a global level. One such social form becoming increasingly popular is network hospitality, which refers visiting or accommodating someone, usually a person you do not know in advance, through hospitality exchange networks such as Couchsurfing. In this study I present a qualitative study on hospitality exchange in the context of Airbnb form the perspective of the users participating in the network as hosts, that is, by offering accommodation for other users of the network for a fee. Airbnb differs from reciprocal type of hospitality exchange that Couchsurfing and most of the other existing hospitality exchange networks foster in that the hosts determine a price for the accommodation they are offering. I refer to this kind of commodified form of network hospitality as monetary network hospitality. My theoretical framework is drawn on Simmels theory of social forms, recent sociological literature on the changing modes of sociality in the current networked era, prior discussions about hospitality from historical, sociological and anthropological sources, and the emerging body of literature on network hospitality. The aim of my study is to increase our understanding of network hospitality as a social form and to shed light to the role of money in mediating and structuring the hospitality exchange and the social interaction it spurs. In my analysis I will deploy Simmel’s notion of sociability, a play form of sociality that gains its value from the interaction itself, as well as his theorization of the effects of money on social relations between individuals, to make sense of the sociality monetary network hospitality brings between the parties of the hospitality exchange. My empirical material consists of eleven semi-structured interviews with Airbnb host. The material was gathered during the summer 2013 in Greater Helsinki area. At this time, there was in total around 400 Airbnb hosts in the area. Participants’ age varied from 22 to 58. Seven of them were male and five female. The interview material is analyzed with theory-bound qualitative content analysis. My analysis shows that engaging in social interaction with people from around the world is an important motive for participating in network hospitality by hosting, also when it offers possibilities for financial gains. My analysis also shows that the hosts want to be in control of whom they accept as guests and often try to select guests that are in some way similar to them. My central finding is that the inclusion money in the hospitality exchange contributes to the hosts’ sense of control and ease in the exchange. The inclusion of money renders to hospitality exchange more structured and formal. However, this does not exclude the possibility for sociable interaction between the host and the guest to occur, but, on the contrary, it may in some cases even contribute for conditions for sociable interaction to occur.
Now showing items 1-2 of 2