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Lawall A.,Hof University of Applied Sciences
Communications in Computer and Information Science | Year: 2016

In all organizations, access assignments are essential in order to ensure data privacy, permission levels and the correct assignment of tasks. Traditionally, such assignments are based on total enumeration, with the consequence that constant effort has to be put into maintaining the assignments. This problem still persists when using abstraction layers, such as group and role concepts, e.g. Access Control Matrix and Role-Based Access Control. Role and group memberships are statically defined and members have to be added and removed constantly. This paper describes a novel approach – Hypergraph-Based Access Control HGAC – to assign human and automatic subjects to access rights in a declarative manner. The approach is based on an organizational metamodel and a declarative language. The language is used to express queries and formulate predicates. Queries define sets of subjects based on their properties and their position in the organizational model. They also contain additional information that causes organization-specific and userdefined relations to be active or inactive depending on predicates. In HGAC, the subjects that have a specific permission are determined by such a query. The query itself is not defined statically but created by traversing a hypergraph path. This allows a structured aggregation of permissions on resources. Consequently, multiple resources can share parts of their queries. © Springer International Publishing Switzerland 2016. Source


Niemann R.,Hof University of Applied Sciences
ICPE 2016 Companion - Companion Publication for 7th ACM/SPEC International Conference on Performance Engineering | Year: 2016

The ability to accurately simulate and predict the metrics (e.g. performance and energy consumption) of data management systems offers several benefits. It can save investments in both time and hardware. A prominent example is the resource planning. Given a specific use case, a datacenter operator is able to find the most performant or most energy efficient configuration without performing benchmarks or aquiring the necessary hardware. Another possibility would be to study the effects of architectural changes without having them implemented. In this paper, Queued Petri Nets were used to predict and to study the performance and energy consumption of a distributed data management system like Cassandra. The prediction accuracy was evaluated and compared to actual experimental results. On average, the predicted and experimental results differ only by 8 percent for the performance and 16 percent for the energy efficiency, respectively. In addition to this, the experimental results of the used Cassandra cluster revealed a super-linear behavior for the performance and a sub-linear one for the energy consumption. © 2016 ACM. Source


Lawall A.,Hof University of Applied Sciences
DATA 2015 - 4th International Conference on Data Management Technologies and Applications, Proceedings | Year: 2015

In all organizations, access assignments are essential in order to ensure data privacy, permission levels and the correct assignment of tasks. Traditionally, such assignments are based on total enumeration, with the consequence that constant effort has to be put into maintaining the assignments. This problem still persists when using abstraction layers, such as group and role concepts, e.g. Access Control Matrix and Role-Based Access Control. Role and group memberships are statically defined and members have to be added and removed constantly. This paper describes a novel approach - Hypergraph-Based Access Control H GAC- to assign human and automatic subjects to access rights in a declarative manner. The approach is based on an organizational (meta-) model and a declarative language. The language is used to express queries and formulate predicates. Queries define sets of subjects based on their properties and their position in the organizational model. They also contain additional information that causes organizational relations to be active or inactive depending on predicates. In H GAC, the subjects that have a specific permission are determined by such a query. The query itself is not defined statically but created by traversing a hypergraph path. This allows a structured aggregation of permissions on resources. Consequently, multiple resources can share parts of their queries. Source


Peinl R.,Hof University of Applied Sciences
Proceedings of the Annual Hawaii International Conference on System Sciences | Year: 2016

In the present mobile climate, both companies as well as their consumers are able to execute various processes at any time in any location using a myriad of wireless technologies. Organizational trends demonstrate that mobile devices are being utilized exponentially more to solve problems from the strategic planning level to the operational level through various departments. This propensity was recently confirmed for Germany in a neoteric IDC study [1]. Utilizing that analysis, this article will evaluate and inspect the scope of such modeling. We will endeavor to define the term "mobile modeling", and our final desideratum will be to present results from an empirical investigation of its requirements and benefits. Finally, we will discuss the future technical implications and conclusions of the model. © 2016 IEEE. Source


Niemann R.,Hof University of Applied Sciences
Proceedings - 2015 IEEE 10th International Conference on Global Software Engineering Workshops, ICGSEW 2015 | Year: 2015

In the last couple of years it became more difficult for end users of data management system to optimize existing systems for performance and energy consumption. The reasons are the big number of data management systems to chose from, extensive use cases and a variety of hardware configurations. The number of factors that influence the performance and energy efficiency rises even more when it comes to distributed data management systems. For instance, in addition to vertical scale-out effects the horizontal scale-out ones have to be considered. This paper introduces an enhanced version of a Queued Petri Nets model whose simulation runs allow to predict and to study the performance and energy consumption of a distributed data management system. In contrast to traditional ways, the simulation runs can reduce both investments in time and hardware. The model's prediction in terms of performance and energy consumption were evaluated and compared with the actual experimental results. The predicted and experimental results for the response times differ by nearly 20 percent on average. © 2015 IEEE. Source

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