A Statically Typed Logic Context Query Language With Parametric Polymorphism and Subtyping

The objective of this thesis is programming language support for context-sensitive program adaptations. Driven by the requirements for context-aware adaptation languages, a statically typed Object-oriented logic Context Query Language  (OCQL) was developed, which is suitable for integration with adaptation languages based on the Java type system. The ambient information considered in context-aware applications often originates from several, potentially distributed sources. OCQL employs the Semantic Web-language RDF Schema to structure and combine distributed context information. OCQL offers parametric polymorphism, subtyping, and a fixed set of meta-predicates. Its type system is based on mode analysis and a subset of Java Generics. For this reason a mode-inference approach for normal logic programs that considers variable aliasing and sharing was extended to cover all-solution predicates. OCQL is complemented by a service-oriented context-management infrastructure that supports the integration of OCQL with runtime adaptation approaches. The applicability of the language and its infrastructure were demonstrated with the context-aware aspect language CSLogicAJ. CSLogicAJ aspects encapsulate context-aware behavior and define in which contextual situation and program execution state the behavior is woven into the running program. The thesis concludes with a case study analyzing how runtime adaptation of mobile applications can be supported by pure object-, service- and context-aware aspect-orientation. Our study has shown that CSLogicAJ can improve the modularization of context-aware applications and reduce anticipation of runtime adaptations when compared to other approaches

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

A Definition, Overview and Taxonomy of Generic Aspect Languages

ABSTRACT. Aspect-orientation promises better modularity than pure object-oriented decomposition. A typical benefit of increased modularity is ease of maintenance, evolution and reuse. However, it has been noted by various researchers that many of the first generation aspect languages do not provide the degree of reusability initially hoped for. In this paper, we argue that the problem of insufficient reusability is due to a lack of support for aspect genericity. We analyze various problems of traditional aspect languages and define aspect genericity to be the ability to concisely express aspect effects that vary depending on the context of a join point known at weave-time, without falling back to runtime 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 the different proposals for generic aspect languages made so far and compare them by showing which part of the possible design space is explored within these languages. Among the reviewed design options we identify predicate-based binding of logic metavariables, uniform genericity and fine-grained genericity as optimal answers to three of the discussed questions. Last but not least, we identify open research problems that are specific to aspect genericity or aggravated in the presence of genericity. We expect that genericity will be a key ingredient of a second generation of aspect languages. It will significantly reduce the dependency of aspects on base programs and will automatically select behavior depending on the weave-time context of a join point in the same way as dynamic binding does depending on the type of a message receiver

Uniform genericity for aspect languages

Abstract. Aspect-oriented programming languages promise to provide better modularity than pure object-oriented decomposition. A typical benefit of increased modularity is ease of maintenance, evolution and reuse. However, it has been noted by various researchers that many of the first generation aspect languages do not provide the degree of reusability initially hoped for. In this paper, we argue that the problem is due to a lack of support for aspect genericity, respectively to a lack of support for a sufficiently powerful kind of genericity. We introduce the concept of uniform genericity for aspect languages and discuss in which ways it goes beyond previous approaches to generic aspects. Then we present LogicAJ, a uniformly generic aspect language. Using LogicAJ as an example, we show how uniform aspect genericity recommends itself for implementing reusable solutions of various problems discussed in literature, ranging from the generic replacement of object instantiation, over verification of constraints and conventions, to the generic implementation of design pattern variants. We believe uniform genericity to be an important ingredient for second generation aspect languages whose aspects are only loosely coupled to base programs, thus easing aspect reuse and independent evolution of aspects and base programs.

newsgroup data set. http://www.ai.mit.edu/ jrennie/20 newsgroups

ABSTRACT. Aspect-oriented programming languages promise to provide better modularity than pure object-oriented decomposition. A typical benefit of increased modularity is ease of maintenance, evolution and reuse. However, it has been noted by various researchers that many of the first generation aspect languages do not provide the degree of reusability initially hoped for. In this paper, we argue that the problem is due to a lack of support for aspect genericity, respectively to a lack of support for a sufficiently powerful kind of genericity. We analyze various problems of non-generic aspect languages and define genericity to be the ability to concisely express aspect effects that vary depending on the context of a join point known at weave-time. We 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 the different proposals for generic aspect languages made so far and compare them by showing which part of the possible design space is explored within these languages. We identify the orthogonal needs for uniform and fine grained genericity in aspect languages and discuss in which ways these concepts go beyond previous approaches to generic aspects. Last but not least, we identify open research problems that are specific to aspect genericity or aggravated in the presence of genericity

Integrating aspect-orientation and structural annotations to support adaptive middleware

To anticipate or not to anticipate — that is the question, re-garding adaptive middleware in the area of ubiquitous com-puting. Anticipation can guarantee that both the adapted and the adapting component work together safely, but it lim-its 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 seman-tic gap between the business logic that triggers the adapta-tion 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

Evolvable Pattern Implementations Need Generic Aspects

Design patterns are a standard means to create large software systems. However, with standard object-oriented techniques, typical implementations of such patterns are not themselves reusable software entities. Evolution of a program into a ‘patterned ’ form (also known as ‘refactoring to patterns’) and subsequent evolution of a ‘patterned ’ design is largely left to the programmer. Due to their ability to encapsulate elements that crosscut different modules, aspect languages have the potential to change this situation. For many interesting patterns, a large part of the process of refactoring to patterns can already be implemented modularly in aspects. Still, existing aspect languages can only express a small number of typical patterns implementations in a generally reusable way. In many cases, evolution of an application that uses one pattern variant into one that uses another one cannot be achieved at all. In others, it requires duplicating parts of the aspect implementation, thus creating scattered code in the aspects and hindering their further evolution. In this paper, we argue that aspect languages need to provide genericity in order to support reusable pattern implementations. We sketch the main features of the generic aspect language LogicAJ, and show how it supports software evolution. In particular, we demonstrate how LogicAJ enables evolution of a non-patterned implementation to a patterned one and easy transition from one patterned implementation to another. 1