The Semantic Web offers access to a vast Web of interlinked information accessible via SPARQL endpoints. Such endpoints offer a well-defined interface to retrieve results for complex SPARQL queries. The computational load for processing such queries, however, lies entirely with the server hosting the SPARQL endpoint, which can easily become overloaded and in the worst case not only become slow in responding but even crash so that the data becomes temporarily unavailable. Recently proposed interfaces, such as Triple Pattern Fragments, have therefore shifted the query processing load from the server to the client. For queries involving triple patterns with low selectivity, this can easily result in high network traffic and slow execution times. In this paper, we therefore present a novel interface, Star Pattern Fragments (SPF), which decomposes SPARQL queries into star-shaped subqueries and can combine a lower network load with a higher query throughput and a comparatively low server load. Our experimental results show that our approach does not only significantly reduce network traffic but is also at least an order of magnitude faster in comparison to the state-of-the-art interfaces under high query processing load.
In recent years, using cell phone log data to model human mobility patterns became an active research area. This problem is a challenging data mining problem due to huge size and the non-uniformity of the log data, which introduces several granularity levels for the specification of temporal and spatial dimensions. This paper focuses on the prediction of the location of the next activity of the mobile phone users. There are several versions of this problem. In this work, we have concentrated on the following three problems: Predicting the location and the time of the next user activity, predicting the location of the next activity of the user when the location of the user changes, and predicting both the location and the time of the activity of the user when the user's location changes. We have developed sequential pattern mining based techniques for these three problems and validated the success of these methods with real data obtained from one of the largest mobile phone operators in Turkey. Our results are very encouraging, since we were able to obtain quite high accuracy results under a small prediction sets.
With the continuously growing amount of data offered in the form of knowledge graphs, users are often overwhelmed by the amount of potentially relevant information and entities. Hence, helping users find relevant data is a problem that becomes more and more important. Skyline queries are typically used in multi-criteria decision making applications to find a set of objects that are of interest to a user. This type of queries has been extensively studied over relational data in the database community. But only little attention has yet been paid to investigating if and how the skyline principle can help identifying sets of interesting entities in knowledge graphs. In this paper, we therefore show how the skyline principle can be applied to RDF knowledge graphs and help the user find interesting entities. In particular, we present algorithms using commonly used standard interfaces for accessing RDF data and a lightweight extension of existing interfaces (SkyTPF) to process skyline queries. Our experiments show that the proposed algorithms enable efficient and scalable skyline query processing over knowledge graphs.
Predicting the location of people from their mobile phone logs is becoming an attractive research area. Due to two main reasons this problem is very challenging: the log data is very large and there is a variety of granularity levels both for specifying the location and the time, especially with low granularity level it becomes much more complicated to define common user behaviour patterns. In this work, rather than determining the next location of a person, we focus on the predicting the location of a person when it changes. We employed a two phase method; which first clusters the data to obtain a higher granularity level, and then extracts frequent sequential patterns corresponding to location changes. We have validated our results with real data obtained from one of the largest mobile phone operators in Turkey. Our results are very encouraging, and we have obtained very high accuracy results in predicting the change of location of mobile phone users.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.