Tobias Rho

A comparison of logic-based infrastructures for concern detection and extraction

In this paper we evaluate logic code analysis and transformation frameworks for their suitability as basic infrastructures for fast detection and extraction of (crosscutting) concerns. Using design patterns as example concerns, we identify desirable properties that an infrastructure should fulfill. We then report our initial results of evaluating candidate systems with respect to these properties. We show how high precision design pattern detectors can be easily formulated as predicates that are evaluated in mere seconds even on the sources of large software systems, such as the Eclipse IDE. Although details still remain to be analyzed further, our current results suggest that the pair JTransformer & CTC is a good candidate for a general infrastructure, combining very good querying performance, scalability and short turn-around times with a seamless integration of querying and transformation capabilities.

Dedicated Programming Support for Context-Aware Ubiquitous Applications

Ubiquitous mobile applications often require dynamic context information for user-specific computation. However, state-of-the-art platforms, frameworks, and programming languages used for developing such applications do not directly support context-dependent behavior with first class entities. Instead, context-aware functionality is tangled with the applications core concerns, which increases complexity, and hinders separation of concerns and further software evolution. This paper motivates Context-oriented Programming (COP) for ubiquitous computing. It presents an overview of our COP extension to the Java programming language and a scenario of a context-oriented mobile application.

A Definition, Overview and Taxonomy of Generic Aspect Languages

Many aspect languages do not provide the degree of aspect reusability initially hoped for. In this paper, we show that the problem stems from lacking support for genericity. Aspect genericity is the ability to express aspect effects that vary depending on the context of a join point, without falling back to run-time reflection. We identify the ability to parameterize aspect effects with meta-variables ranging over base language elements as the technical prerequisite for achieving genericity and describe the design space for generic aspect languages in terms of five basic questions that a language designer should consider. Within this space we review existing proposals for generic aspect languages, and discuss which part of the possible design space they explore. Finally, we identify open problems they are specific to aspect genericity or aggravated in the presence of genericity.

A context management infrastructure with language integration support

A range of context-management systems in the past have motivated the need for development support of context-aware applications. They typically provide APIs and query languages for context analysis. Reacting to context changes, however, is either not at all or only to a limited extend supported by adhering to constraints of a framework. In this paper, we present a context-management system that combines context reasoning with context-dependent behavior by taking advantage of language approaches to dynamic adaptation, such as aspect- and context-oriented programming. Our framework is open for different levels of integration with programming language extensions and offers a dynamic, strategy-based aggregation of local and distributed context sources. As a first step, we implemented a query library for the JCop language. We present its API and show the implementation of an example application.

Integrating aspect-orientation and structural annotations to support adaptive middleware

To anticipate or not to anticipate --- that is the question, regarding adaptive middleware in the area of ubiquitous computing. Anticipation can guarantee that both the adapted and the adapting component work together safely, but it limits the scenario space to some predictable well-known cases. This holds even more when statically typed languages are used, as we assume here. A second problem is a semantic gap between the business logic that triggers the adaptation and the technological demands of the adaptation that must be solved on the implementation level. We discuss current approaches and describe a new approach combining aspect-oriented programming with structural metadata to cope with both problems. An example illustrates how our approach will work in practice.

Towards context-sensitive intelligence

Even modern component architectures do not provide for easily manageable context-sensitive adaptability, a key requirement for ambient intelligence. The reason is that components are too large – providing black boxes with adaptation points only at their boundaries – and to small – lacking good means for expressing concerns beyond the scope of single components – at the same time. We present a framework that makes components more fine-grained so that adaptation points inside of them become accessible, and more coarse-grained so that changes of single components result in the necessary update of structurally constrained dependants. This will lead to higher quality applications that fit better into personalized and context-aware usage scenarios.

Performance-optimized indexes for inequality searches on encrypted data in practice

For information systems in which the server must operate on encrypted data (which may be necessary because the service provider cannot be trusted) solutions need to be found that enable fast searches on that data. In this paper we present an approach for encrypted database indexes that enable fast inequality, i.e., range searches, such that also prefix searches on lexicographically ordered but encrypted data are possible. Unlike common techniques that address this issue as well, like hardware-based solutions or order-preserving encryption schemes, our indexes do not require specialized, expensive hardware and use only well-accredited software components; they also do not reveal any information about the encrypted data besides their order. Moreover, when implementing the indexing approach in a commercial software product, multiple application-centric optimization opportunities of the indexs performance did emerge, which are also presented in this paper. They include basic performance-increasing measures, pipelined index scans and updates and caching strategies. We further present performance test results proving that our indexing approach shows good performance on substantial amounts of data.