XQuery Streaming by Forest Transducers

Streaming of XML transformations is a challenging task and only very few systems support streaming. Research approaches generally define custom fragments of XQuery and XPath that are amenable to streaming, and then design custom algorithms for each fragment. These languages have several shortcomings. Here we take a more principles approach to the problem of streaming XQuery-based transformations. We start with an elegant transducer model for which many static analysis problems are well-understood: the Macro Forest Transducer (MFT). We show that a large fragment of XQuery can be translated into MFTs --- indeed, a fragment of XQuery, that can express important features that are missing from other XQuery stream engines, such as GCX: our fragment of XQuery supports XPath predicates and let-statements. We then rely on a streaming execution engine for MFTs, one which uses a well-founded set of optimizations from functional programming, such as strictness analysis and deforestation. Our prototype achieves time and memory efficiency comparable to the fastest known engine for XQuery streaming, GCX. This is surprising because our engine relies on the OCaml built in garbage collector and does not use any specialized buffer management, while GCX's efficiency is due to clever and explicit buffer management.Comment: Full version of the paper in the Proceedings of the 30th IEEE International Conference on Data Engineering (ICDE 2014

XCSL: XML constraint specification language

After being able to mark-up text and validate its structure according to a document type specification, we may start thinking it would be natural to be able to validate some nonstructural issues in the documents. This paper is to formally discuss semantic-related aspects. In that context, we introduce a domain specific language developed for such a purpose: XCSL. XCSL is not just a language, it is also a processing model. Furthermore, we discuss the general philosophy underlying the proposed approach, presenting the architecture of our semantic validation system, and we detail the respective processor. To illustrate the use of XCSL language and the subsequent processing, we present two case-studies. Nowadays, we can find some other languages to restrict XML documents to those semantically valid - namely Schematron and XML-Schema. So, before concluding the paper, we compare XCSL to those approaches

CAIN-21: Automatic adaptation decisions and extensibility in an MPEG-21 adaptation engine

This paper presents the progress and final state of CAIN-21, an extensible and metadata driven multimedia adaptation in the MPEG-21 framework. CAIN-21 facilitates the integration of pluggable multimedia adaptation tools, automatically chooses the chain of adaptations to perform and manages its execution. To drive the adaptation, it uses the description tools and implied ontology established by MPEG-21. The paper not only describes the evolution and latest version of CAIN-21, but also identifies limitations and ambiguities in the description capabilities of MPEG-21. Therefore, it proposes some extensions to the MPEG-21 description schema for removing these problems. Finally, the pros and cons of CAIN-21 with respect to other multimedia adaptation engines are discussed