We present results of a thorough analysis of the OpenPGP Web of Trust. We conducted our analysis on a recent data set with a focus on determining properties like usefulness and robustness. To this end, we analyzed graph topology, identified the strongly connected components and derived properties like verifiability of keys, signature chain lengths and redundant signature paths for nodes. Contrary to earlier works, our analysis revealed the Web of Trust to be only similar to a scale-free network, with different properties regarding the hub structure and its influence on overall connectivity. We also analyzed the community structure of the Web of Trust and mapped it to social relationships. Finally, we present statistics which cryptographic algorithms are in use and give recommendations.

We demonstrate the insides and outs of a query compiler based on the flattening transformation, a translation technique designed by the programming language community to derive efficient data-parallel implementations from iterative programs. Flattening admits the straightforward formulation of intricate query logic-including deeply nested loops over (possibly ordered) data or the construction of rich data structures. To demonstrate the level of expressiveness that can be achieved, we will bring a compiler frontend that accepts queries embedded into the Haskell programming language. Compilation via flattening takes places in a series of simple steps all of which will be made tangible by the demonstration. The final output is a program of lifted primitive operations which existing query engines can efficiently implement. We provide backends based on PostgreSQL and VectorWise to make this point-however, most set-oriented or data-parallel engines could benefit from a flattening-based query compiler.

The seamless integration of relational databases and programming languages remains a major challenge. Mapping rich data types featured in general-purpose programming languages to the relational data model is one aspect of this challenge. We present a novel technique for mapping arbitrary (nonrecursive) algebraic data types to a relational data model, based on previous work on the relational representation of nested tables. Algebraic data types may be freely constructed and deconstructed in queries and may show up in the result type. The number of relational queries generated is small and statically determined by the type of the query. We have implemented the mapping in the Database Supported Haskell (DSH) library.

Eckehard Schnieder zum 60. Geburtstag gewidmet Der Beitrag zeigt, wie mit Hilfe der formalisierten Prozessbeschreibung, der VDI/VDERichtlinie 3682 entsprechend, verfahrenstechnische und fertigungstechnische Prozesse abgebildet werden können, bis hinunter auf die Ebene einzelner Stelleingriffe. Dabei wurde ,,Information" explizit graphisch dargestellt. Eine entsprechende Ergänzung der formalisierten Prozessbeschreibungen um dieses zusätzliche Element wird zur Diskussion gestellt.In this paper, the formal process description according to ''VDI/VDE-Richtlinie 3682" is applied to both process automation and factory automation. Following a top-down methodology, the description of the technical procsss is refined to the level of detail of single control actions. The explicit graphical representation of ''information", in addition to material and energy flow, is useful for this purpose, as it can help to describe parallel and alternative sub-processes, and synchronisation between them.

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