Markus L. Noga

Lazy XML processing

This paper formalizes the domain of tree-based XML processing and classifies several implementation approaches. The lazy approach, an original contribution, is presented in depth. Proceeding from experimental measurements, we derive a selection strategy for implementation approaches to maximize performance.

Foundations of Fast Communication via XML

Communication with XML often involves pre-agreed document types. In this paper, we propose an offline parser generation approach to enhance online processing performance for documents conforming to a given DTD. Our examination of DTDs and the languages they define demonstrates the existence of ambiguities. We present an algorithm that maps DTDs to deterministic context-free grammars defining the same languages. We prove the grammars to be LL(1) and LALR(1), making them suitable for standard parser generators. Our experiments show the superior performance of generated optimized parsers. Our results generalize from DTDs to XML schema specifications with certain restrictions, most notably the absence of namespaces, which exceed the scope of context-free grammars.

Lazy XSL transformations

We introduce a lazy XSLT interpreter that provides random access to the transformation result. This allows efficient pipelining of transformation sequences. Nodes of the result tree are computed only upon initial access. As these computations have limited fan-in, sparse output coverage propagates backwards through the pipeline.In comparative measurements with traditional eager implementations, our approach is on par for complete coverage and excels as coverage becomes sparser. In contrast to eager evaluation, lazy evaluation also admits infinite intermediate results, thus extending the design space for transformation sequences.To demonstrate that lazy evaluation preserves the semantics of XSLT, we reduce XSLT to the lambda calculus via a functional language. While this is possible for all languages, most imperative languages cannot profit from the confluence of lambda as only one reduction applies at a time.

Metaprogramming Applied to Web Component Deployment

Metaprogramming is a generic approach described in many articles. Surprisingly, examples of successful applications are scarce. This paper gives such an example. With a metaprogram of less than 2500 lines, we deploy components on the web by adding specific XML-based communication facilities. This underlines the expressiveness of the metaprogramming approach.

Optimizing Content Management System Pipelines Separation and Merging of Concerns

Content management systems support the dissemination and maintenance of documents. In software engineering terms, they separate the concerns of content, application logic and visual styling. Current systems largely maintain this separation of concerns after document deployment. Their runtime processing pipeline is a composition of generators, or document transformations. We exploit commutativity to enable new static evaluations of the composite during document deployment. Unlike traditional caching, we arrive at closed-form composites even for styled, database-driven documents. This eliminates the runtime penalties of a separation of concerns while preserving their software engineering benefits.

Scenario-Based Connector Optimization An XML Approach

Software components can be connected by XML processing pipelines, which may perform adaptations. In our model, individual pipeline stages serialize source data structures to XML, perform one or multiple XSL transformations, transport the message to its destination and finally deserialize it to target data structures. Implementation of this model is open to optimizations. The present paper discusses two such optimizations: symbolic execution and lazy evaluation.

Specification in a large industry consortium-the MOST approach

The MOST Cooperation (media-oriented systems transport) is an industry group of automotive and supplier companies that specifies interfaces of multimedia components. Many members are competitors: they collaborate on standards while preserving their competitive advantages. Moreover, development processes differ for each member, but the MOST standard must be concise and consistent. We develop an XML based architecture to support individual workflows and the specification process as a whole.

Manchmal ist der wichtigste Baustein kein Baustein

Italian LEGO Users Group am 26. März ihre vierte Vollversammlung abhielt.