Platform as a service model has certain obstacles, including data lock-in. It is expensive and time-consuming to move data to the alternative providers. This paper presents data storage options in platform as a service offers and identifies the most common data portability problems between various commercial providers of platform as a service. There are differences among their storage models, data types, remote APIs for data manipulation and query languages. Representing data models of platform as a service and data mappings by means of ontology can provide a common layer to achieve data portability among different cloud providers.
The scientific knowledge is disseminated by research papers. Most of the research literature is copyrighted by publishers and avail- able only through paywalls. Recently, some websites offer most of the recent content for free. One of them is the controversial website Sci-Hub that enables access to more than 47 million pirated research papers. In April 2016, Science Magazine published an article on Sci-Hub activity over the period of six months and publicly released the Sci-Hub’s server log data. The mentioned paper aggregates the view that relies on all downloads and for all fields of study, but these findings might be hiding interesting patterns within computer science. The mentioned Sci-Hub log data was used in this paper to analyse downloads of computer science papers based on DBLP’s list of computer science publications. The top downloads of computer science papers were analysed, together with the geographical location of Sci-Hub users, the most downloaded publishers, types of papers downloaded, and downloads of computer science papers per publication year. The results of this research can be used to improve legal access to the most relevant scientific repositories or journals for the computer science field.
Ontologies can be used to describe common cloud functionalities and enable common terminology to assist in cloud interoperability. In this work, we have developed the ontology for resources and operations and the ontology of interoperability problems. The aim is to clearly describe and categorize the existing functionalities, features and specificities of commercial platform asaservice offers. The first ontology also provides data type mappings among different Paa Sstorages and cross-Paa Sdata types used in inputs and outputs of the remote APIoperations to provideacommon layer for information exchange and data migration among different Paa Sproviders. The ontologies were evaluated by tools and by human experts. Furthermore, the ontologies were used in cloud interoperability prototype to show their practical applicability.