A structural analysis of the A5/1 state transition graph

We describe efficient algorithms to analyze the cycle structure of the graph induced by the state transition function of the A5/1 stream cipher used in GSM mobile phones and report on the results of the implementation. The analysis is performed in five steps utilizing HPC clusters, GPGPU and external memory computation. A great reduction of this huge state transition graph of 2^64 nodes is achieved by focusing on special nodes in the first step and removing leaf nodes that can be detected with limited effort in the second step. This step does not break the overall structure of the graph and keeps at least one node on every cycle. In the third step the nodes of the reduced graph are connected by weighted edges. Since the number of nodes is still huge an efficient bitslice approach is presented that is implemented with NVIDIA's CUDA framework and executed on several GPUs concurrently. An external memory algorithm based on the STXXL library and its parallel pipelining feature further reduces the graph in the fourth step. The result is a graph containing only cycles that can be further analyzed in internal memory to count the number and size of the cycles. This full analysis which previously would take months can now be completed within a few days and allows to present structural results for the full graph for the first time. The structure of the A5/1 graph deviates notably from the theoretical results for random mappings.Comment: In Proceedings GRAPHITE 2012, arXiv:1210.611

What is a good textual representation of activity diagrams in requirements documents?

The use of graphical models has become a widely adopted approach to specify requirements of complex systems. Still, in practice, graphical models are often accompanied by textual descriptions to provide more detail, because of legal considerations, and to enable stakeholders with different backgrounds to understand a requirements document. One of our industry partners (Daimler AG) uses activity diagrams to specify vehicle functions in combination with a textual representation thereof in their requirements documents. Since graphical and textual representations serve different purposes, it is not obvious how textual representations of activity diagrams should be structured. In this paper, we present different textual representations of activity diagrams for use in requirements documents. The representation currently in use is presented as well as four alternatives. For each representation, we discuss advantages and disadvantages. To evaluate the representations, we asked five stakeholders of one system to create a preference ranking of the representations. The resulting ranking showed that the currently used representation is not considered to be the best possible option. The stakeholders’ favorite textual representation emphasizes structural similarity with the activity diagram, which however does not resemble the diagram’s structure exactly

Evaluation of a specification approach for vehicle functions using activity diagrams in requirements documents

Rising complexity of systems has long been a major challenge in requirements engineering. This manifests in more extensive and harder to understand requirements documents. At the Daimler AG, an approach is applied that combines the use of activity diagrams with natural language specifications to specify vehicle functions. The approach starts with an activity diagram that is created to get an early overview. The contained information is then transferred to a textual requirements document, where details are added and the behavior is refined. While the approach aims at reducing efforts needed to understand a function’s behavior, the application of the approach itself causes new challenges on its own. By examining existing specifications at Daimler, we identified nine categories of inconsistencies and deviations between activity diagrams and their textual representations. This paper extends a previous case study on the subject by presenting additional data we acquired. Our analysis indicates that a coexistence of textual and graphical representations of models without proper tool support results in inconsistencies and deviations

Coexisting graphical and structured textual representations of requirements : insights and suggestions

[Context & motivation] Many requirements documents contain graphical and textual representations of requirements side-byside. These representations may be complementary but oftentimes they are strongly related or even express the same content. [Question/problem] Since both representation may be used on their own, we want to nd out why and how a combination of them is used in practice. In consequence, we want to know what advantages such an approach provides and whether challenges arise from the coexistence. [Principal ideas/results] To get more insights into how graphical and textual representations are used in requirements documents, we conducted eight interviews with stakeholders at Daimler. These stakeholders work on a system that is speci ed by tabular textual descriptions and UML activity diagrams. The results indicate that the di erent representations are associated with di erent activities. [Contribution] Our study provides insights into a possible implementation of a speci cation approach using mixed representations of requirements. We use these insights to make suggestions on how to apply the approach in a way that pro ts from its advantages and mitigates potential weaknesses. While we draw our conclusions from a single use case, some aspects might be applicable in general

Information extraction from high-level activity diagrams to support development tasks

As the complexity of systems continues to increase, the use of model-driven development approaches becomes more widely applied. One of our industry partners (Daimler AG) uses UML activity diagrams as the first step in the development of vehicle functions, mainly for the purpose of communication and overview. However, the contained information is also valuable for further development tasks. In this paper, we present an automated approach to extract information from these high-level activities. We put a focus on aspects of activities such as propositional logic relations, sequences of actions, and differentiability of execution paths. The extracted parts are needed for the compilation of requirements and the creation of test cases. Also, this approach supports stakeholders unfamiliar with the notations of activities as implicit information is made explicit and hence more accessible. For this purpose, we provide a formalism for the kind of activities our industry partner uses. Based on that formalism, we define properties that express the contained sequences and execution paths. Furthermore, the formalism is used to derive the underlying propositional logic relations. We show how the approach is applied to eliminate hundreds of existing quality issues in an existing requirements document

A case study on a specification approach using activity diagrams in requirements documents

Rising complexity of systems has long been a major challenge in requirements engineering. This manifests in more extensive and harder to understand requirements documents. At the Daimler AG, an approach is applied that combines the use of activity diagrams with natural language specifications to specify system functions. The approach starts with an activity diagram that is created to get an early overview. The contained information is then transferred to a textual requirements document, where details are added and the behavior is refined. While the approach aims to reduce efforts needed to understand a system’s behavior, the application of the approach itself causes new challenges on its own. By examining existing specifications at Daimler, we identified nine categories of inconsistencies and deviations between activity diagrams and their textual representations. In a case study, we examined one system in detail to assess how often these occur. In a follow-up survey, we presented instances of the categories to different stakeholders of the system and let them asses the categories regarding their severity. Our analysis indicates that a coexistence of textual and graphical representations of models without proper tool support results in inconsistencies and deviations that may cause severe maintenance costs or even provoke faults in subsequent development steps

Traceability Analysis of a High-Level Automotive System Architecture Document

More and more functions in automotive systems are enabled and controlled by software that is distributed over a large number of systems and components. In addition, the systems are more and more interconnected to implement the desired vehicle functions. Creating and maintaining a high-level overview of the relations between vehicle functions, systems, and components in a complete and consistent way requires a lot of effort. On the other hand, such a high-level architecture is beneficial for planning the development, analyzing the architecture, or defining product variants. In this paper, we analyze a real-world document that was manually created to document all vehicle functions, systems, and components of one car series and relations between these. We formalized the content of this model by providing a model of the concepts and a set of consistency rules. By evaluating the consistency rules on the given document, we found 213 contradictory relations and 547 missing relations. Based on these results, we conclude that manually maintaining such high-level architectures is highly error-prone and should thus be supported by automation and appropriate tooling

TeCoMiner: Topic Discovery Through Term Community Detection

This note is a short description of TeCoMiner, an interactive tool for exploring the topic content of text collections. Unlike other topic modeling tools, TeCoMiner is not based on some generative probabilistic model but on topological considerations about co-occurrence networks of terms. We outline the methods used for identifying topics, describe the features of the tool, and sketch an application, using a corpus of policy related scientific news on environmental issues published by the European Commission over the last decade.Comment: 8 pages, 4 figure

Removal of redundant elements within UML activity diagrams

As the complexity of systems continues to rise, the use of model-driven development approaches becomes more widely applied. Still, many created models are mainly used for documentation. As such, they are not designed to be used in following stages of development, but merely as a means of improved overview and communication. In an effort to use existing UML2 activity diagrams of an industry partner (Daimler AG) as a source for automatic generation of software artifacts, we discovered, that the diagrams often contain multiple instances of the same element. These redundant instances might improve the readability of a diagram. However, they complicate further approaches such as automated model analysis or traceability to other artifacts because mostly redundant instances must be handled as one distinctive element. In this paper, we present an approach to automatically remove redundant ExecutableNodes within activity diagrams as they are used by our industry partner. The removal is implemented by merging the redundant instances to a single element and adding additional elements to maintain the original behavior of the activity. We use reachability graphs to argue that our approach preserves the behavior of the activity. Additionally, we applied the approach to a real system described by 36 activity diagrams. As a result 25 redundant instances were removed from 15 affected diagrams

The Top Three Burning Questions in Total Hip Arthroplasty.

Total hip arthroplasty (THA) for end-stage osteoarthritis is one of the most effective surgical treatments in medicine. Impressive outcomes have been well documented in the literature with patients gaining ambulation and recovery of hip joint function. Nevertheless, there are still debatable issues and controversies that the orthopedic community has not been able to provide a definitive answer for. This review is focused on the current three most debatable issues surrounding the THA procedure: (1) new cutting-edge technology, (2) spinopelvic mobility, and (3) fast-track protocols. The scope of the herein narrative review is to analyze the debatable issues surrounding the three aforementioned topics and conclude the best contemporary clinical approaches regarding each issue