@article{HirschfeldKawarnura2006,
  author    = {Hirschfeld, Robert and Kawarnura, Katsuya},
  title     = {Dynamic service adaptation},
  series = {Software : practice \& experience},
  volume    = {36},
  journal   = {Software : practice \& experience},
  number    = {11-12},
  publisher = {Wiley},
  address   = {Chichester},
  issn      = {0038-0644},
  doi       = {10.1002/spe.766},
  pages     = {1115 -- 1131},
  year      = {2006},
  abstract  = {Change can be observed in our environment and in the technology we build. While changes in the environment happen continuously and implicitly, our technology has to be kept in sync with the changing world around it. Although we can prepare for some of the changes for most of them we cannot. This is especially true for next-generation mobile communication systems that are expected to support the creation of a ubiquitous society where virtually everything is connected and made available within an organic information network. Resources will frequently join or leave the network, new types of media or new combinations of existing types will be used to interact and cooperate, and services will be tailored to preferences and needs of individual customers to better meet their needs. This paper outlines our research in the area of dynamic service adaptation to provide concepts and technologies allowing for such environments. Copyright (C) 2006 John Wiley \& Sons, Ltd.},
  language  = {en}
}
@article{HauptAdamsTimbermontetal.2009,
  author    = {Haupt, Michael and Adams, Bram and Timbermont, Stijn and Gibbs, Celina and Coady, Yvonne and Hirschfeld, Robert},
  title     = {Disentangling virtual machine architecture},
  issn      = {1751-8806},
  doi       = {10.1049/iet-sen.2007.0121},
  year      = {2009},
  abstract  = {Virtual machine (VM) implementations are made of intricately intertwined subsystems, interacting largely through implicit dependencies. As the degree of crosscutting present in VMs is very high, VM implementations exhibit significant internal complexity. This study proposes an architecture approach for VMs that regards a VM as a composite of service modules coordinated through explicit bidirectional interfaces. Aspect-oriented programming techniques are used to establish these interfaces, to coordinate module interaction, and to declaratively express concrete VM architectures. A VM architecture description language is presented in a case study, illustrating the application of the proposed architectural principles.},
  language  = {en}
}
@article{HirschfeldSteinertLincke2011,
  author    = {Hirschfeld, Robert and Steinert, Bastian and Lincke, Jens},
  title     = {Agile software development in virtual collaboration environments},
  isbn      = {978-3-642-13756-3},
  year      = {2011},
  language  = {en}
}
@article{LinckeAppeltauerSteinertetal.2011,
  author    = {Lincke, Jens and Appeltauer, Malte and Steinert, Bastian and Hirschfeld, Robert},
  title     = {An open implementation for context-oriented layer composition in ContextJS},
  series = {Science of computer programming},
  volume    = {76},
  journal   = {Science of computer programming},
  number    = {12},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0167-6423},
  doi       = {10.1016/j.scico.2010.11.013},
  pages     = {1194 -- 1209},
  year      = {2011},
  abstract  = {Context-oriented programming (COP) provides dedicated support for defining and composing variations to a basic program behavior. A variation, which is defined within a layer, can be de-/activated for the dynamic extent of a code block. While this mechanism allows for control flow-specific scoping, expressing behavior adaptations can demand alternative scopes. For instance, adaptations can depend on dynamic object structure rather than control flow. We present scenarios for behavior adaptation and identify the need for new scoping mechanisms. The increasing number of scoping mechanisms calls for new language abstractions representing them. We suggest to open the implementation of scoping mechanisms so that developers can extend the COP language core according to their specific needs. Our open implementation moves layer composition into objects to be affected and with that closer to the method dispatch to be changed. We discuss the implementation of established COP scoping mechanisms using our approach and present new scoping mechanisms developed for our enhancements to Lively Kernel.},
  language  = {en}
}
@article{SteinertHirschfeld2012,
  author    = {Steinert, Bastian and Hirschfeld, Robert},
  title     = {Applying design knowledge to programming},
  year      = {2012},
  language  = {en}
}
@article{HirschfeldPerscheidHaupt2012,
  author    = {Hirschfeld, Robert and Perscheid, Michael and Haupt, Michael},
  title     = {Explicit use-case representation in object-oriented programming languages},
  series = {ACM SIGPLAN notices},
  volume    = {47},
  journal   = {ACM SIGPLAN notices},
  number    = {2},
  publisher = {Association for Computing Machinery},
  address   = {New York},
  issn      = {0362-1340},
  doi       = {10.1145/2168696.2047856},
  pages     = {51 -- 60},
  year      = {2012},
  abstract  = {Use-cases are considered an integral part of most contemporary development processes since they describe a software system's expected behavior from the perspective of its prospective users. However, the presence of and traceability to use-cases is increasingly lost in later more code-centric development activities. Use-cases, being well-encapsulated at the level of requirements descriptions, eventually lead to crosscutting concerns in system design and source code. Tracing which parts of the system contribute to which use-cases is therefore hard and so limits understandability. In this paper, we propose an approach to making use-cases first-class entities in both the programming language and the runtime environment. Having use-cases present in the code and the running system will allow developers, maintainers, and operators to easily associate their units of work with what matters to the users. We suggest the combination of use-cases, acceptance tests, and dynamic analysis to automatically associate source code with use-cases. We present UseCasePy, an implementation of our approach to use-case-centered development in Python, and its application to the Django Web framework.},
  language  = {en}
}
@article{SteinertCassouHirschfeld2013,
  author    = {Steinert, Bastian and Cassou, Damien and Hirschfeld, Robert},
  title     = {CoExist overcoming aversion to change preserving immediate access to source code and run-time information of previous development states},
  series = {ACM SIGPLAN notices},
  volume    = {48},
  journal   = {ACM SIGPLAN notices},
  number    = {2},
  publisher = {Association for Computing Machinery},
  address   = {New York},
  issn      = {0362-1340},
  doi       = {10.1145/2480360.2384591},
  pages     = {107 -- 117},
  year      = {2013},
  abstract  = {Programmers make many changes to the program to eventually find a good solution for a given task. In this course of change, every intermediate development state can of value, when, for example, a promising ideas suddenly turn out inappropriate or the interplay of objects turns out more complex than initially expected before making changes. Programmers would benefit from tool support that provides immediate access to source code and run-time of previous development states of interest. We present IDE extensions, implemented for Squeak/Smalltalk, to preserve, retrieve, and work with this information. With such tool support, programmers can work without worries because they can rely on tools that help them with whatever their explorations will reveal. They no longer have to follow certain best practices only to avoid undesired consequences of changing code.},
  language  = {en}
}
@article{WeiherHirschfeld2014,
  author    = {Weiher, Marcel and Hirschfeld, Robert},
  title     = {Polymorphic identifiers: uniform resource access in objective-smalltalk},
  series = {ACM SIGPLAN notices},
  volume    = {49},
  journal   = {ACM SIGPLAN notices},
  number    = {2},
  publisher = {Association for Computing Machinery},
  address   = {New York},
  issn      = {0362-1340},
  doi       = {10.1145/2508168.2508169},
  pages     = {61 -- 71},
  year      = {2014},
  abstract  = {In object-oriented programming, polymorphic dispatch of operations decouples clients from specific providers of services and allows implementations to be modified or substituted without affecting clients. The Uniform Access Principle (UAP) tries to extend these qualities to resource access by demanding that access to state be indistinguishable from access to operations. Despite language features supporting the UAP, the overall goal of substitutability has not been achieved for either alternative resources such as keyed storage, files or web pages, or for alternate access mechanisms: specific kinds of resources are bound to specific access mechanisms and vice versa. Changing storage or access patterns either requires changes to both clients and service providers and trying to maintain the UAP imposes significant penalties in terms of code-duplication and/or performance overhead. We propose introducing first class identifiers as polymorphic names for storage locations to solve these problems. With these Polymorphic Identifiers, we show that we can provide uniform access to a wide variety of resource types as well as storage and access mechanisms, whether parametrized or direct, without affecting client code, without causing code duplication or significant performance penalties.},
  language  = {en}
}
@article{BaumanBolzHirschfeldetal.2015,
  author    = {Bauman, Spenser and Bolz, Carl Friedrich and Hirschfeld, Robert and Kirilichev, Vasily and Pape, Tobias and Siek, Jeremy G. and Tobin-Hochstadt, Sam},
  title     = {Pycket: A Tracing JIT for a Functional Language},
  series = {ACM SIGPLAN notices},
  volume    = {50},
  journal   = {ACM SIGPLAN notices},
  number    = {9},
  publisher = {Association for Computing Machinery},
  address   = {New York},
  issn      = {0362-1340},
  doi       = {10.1145/2784731.2784740},
  pages     = {22 -- 34},
  year      = {2015},
  abstract  = {We present Pycket, a high-performance tracing JIT compiler for Racket. Pycket supports a wide variety of the sophisticated features in Racket such as contracts, continuations, classes, structures, dynamic binding, and more. On average, over a standard suite of benchmarks, Pycket outperforms existing compilers, both Racket's JIT and other highly-optimizing Scheme compilers. Further, Pycket provides much better performance for Racket proxies than existing systems, dramatically reducing the overhead of contracts and gradual typing. We validate this claim with performance evaluation on multiple existing benchmark suites. The Pycket implementation is of independent interest as an application of the RPython meta-tracing framework (originally created for PyPy), which automatically generates tracing JIT compilers from interpreters. Prior work on meta-tracing focuses on bytecode interpreters, whereas Pycket is a high-level interpreter based on the CEK abstract machine and operates directly on abstract syntax trees. Pycket supports proper tail calls and first-class continuations. In the setting of a functional language, where recursion and higher-order functions are more prevalent than explicit loops, the most significant performance challenge for a tracing JIT is identifying which control flows constitute a loop-we discuss two strategies for identifying loops and measure their impact.},
  language  = {en}
}
@article{FreudenbergIngallsFelgentreffetal.2015,
  author    = {Freudenberg, Bert and Ingalls, Dan and Felgentreff, Tim and Pape, Tobias and Hirschfeld, Robert},
  title     = {SqueakJS A Modern and Practical Smalltalk that Runs in Any Browser},
  series = {ACM SIGPLAN notices},
  volume    = {50},
  journal   = {ACM SIGPLAN notices},
  number    = {2},
  publisher = {Association for Computing Machinery},
  address   = {New York},
  issn      = {0362-1340},
  doi       = {10.1145/10.1145/2661088.2661100},
  pages     = {57 -- 66},
  year      = {2015},
  abstract  = {We report our experience in implementing SqueakJS, a bitcompatible implementation of Squeak/Smalltalk written in pure JavaScript. SqueakJS runs entirely in theWeb browser with a virtual file system that can be directed to a server or client-side storage. Our implementation is notable for simplicity and performance gained through adaptation to the host object memory and deployment leverage gained through the Lively Web development environment. We present several novel techniques as well as performance measurements for the resulting virtual machine. Much of this experience is potentially relevant to preserving other dynamic language systems and making them available in a browser-based environment.},
  language  = {en}
}