589 research outputs found
Extracting partition statistics from semistructured data
The effective grouping, or partitioning, of semistructured data is of fundamental importance when providing support for queries. Partitions allow items within the data set that share common structural properties to be identified efficiently. This allows queries that make use of these properties, such as branching path expressions, to be accelerated. Here, we evaluate the effectiveness of several partitioning techniques by establishing the number of partitions that each scheme can identify over a given data set. In particular, we explore the use of parameterised indexes, based upon the notion of forward and backward bisimilarity, as a means of partitioning semistructured data; demonstrating that even restricted instances of such indexes can be used to identify the majority of relevant partitions in the data
Dynamic Choreographies: Theory And Implementation
Programming distributed applications free from communication deadlocks and
race conditions is complex. Preserving these properties when applications are
updated at runtime is even harder. We present a choreographic approach for
programming updatable, distributed applications. We define a choreography
language, called Dynamic Interaction-Oriented Choreography (AIOC), that allows
the programmer to specify, from a global viewpoint, which parts of the
application can be updated. At runtime, these parts may be replaced by new AIOC
fragments from outside the application. AIOC programs are compiled, generating
code for each participant in a process-level language called Dynamic
Process-Oriented Choreographies (APOC). We prove that APOC distributed
applications generated from AIOC specifications are deadlock free and race free
and that these properties hold also after any runtime update. We instantiate
the theoretical model above into a programming framework called Adaptable
Interaction-Oriented Choreographies in Jolie (AIOCJ) that comprises an
integrated development environment, a compiler from an extension of AIOCs to
distributed Jolie programs, and a runtime environment to support their
execution.Comment: arXiv admin note: text overlap with arXiv:1407.097
Dynamic Choreographies - Safe Runtime Updates of Distributed Applications
Programming distributed applications free from communication deadlocks and
races is complex. Preserving these properties when applications are updated at
runtime is even harder. We present DIOC, a language for programming distributed
applications that are free from deadlocks and races by construction. A DIOC
program describes a whole distributed application as a unique entity
(choreography). DIOC allows the programmer to specify which parts of the
application can be updated. At runtime, these parts may be replaced by new DIOC
fragments from outside the application. DIOC programs are compiled, generating
code for each site, in a lower-level language called DPOC. We formalise both
DIOC and DPOC semantics as labelled transition systems and prove the
correctness of the compilation as a trace equivalence result. As corollaries,
DPOC applications are free from communication deadlocks and races, even in
presence of runtime updates.Comment: Technical Repor
Compressed materialised views of semi-structured data
Query performance issues over semi-structured data have led to the emergence of materialised XML views as a means of restricting the data structure processed by a query. However preserving the conventional representation of such views remains a significant limiting factor especially in the context of mobile devices where processing power, memory usage and bandwidth are significant factors. To explore the concept of a compressed materialised view, we extend our earlier work on structural XML compression to produce a combination of structural summarisation and data compression techniques. These techniques provide a basis for efficiently dealing with both structural queries and valuebased predicates. We evaluate the effectiveness of such a scheme, presenting results and performance measures that show advantages of using such structures
Topology, randomness and noise in process calculus
Formal models of communicating and concurrent systems are one of the most important topics in formal methods, and process calculus is one of the most successful formal models of communicating and concurrent systems. In the previous works, the author systematically studied topology in process calculus, probabilistic process calculus and pi-calculus with noisy channels in order to describe approximate behaviors of communicating and concurrent systems as well as randomness and noise in them. This article is a brief survey of these works. © Higher Education Press 2007
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