1,721,050 research outputs found
SWOWS and dynamic queries to build browsing applications: On linked data
No full textThe linked data initiative is pushing dataset maintainers to publish data online in a highly reusable way through a set of open standards, such as RDF and SPARQL. The variety and amount of structured data available on the Web are increasing, but their consumption is still quite limited. In particular, applications that are used to explore linked data are usually generic linked data browsers or applications with hard-coded logic tailored for specific needs. SWOWS is a platform for declarative specification of applications con-suming linked data. In this paper, we describe the use of the platform for creating browsing applications tailored to specific contexts, and show how the declarative paradigm supports the development of flexible applications. To this end, the platform has been extended to support the dynamic generation of SPARQL queries. An example of a linked data browser created with the platform is given
Transactions and contracts based on reaction systems
No full textSmart contracts are currently en vogue, thanks to the infrastructure provided by the blockchain technology. However, their effective use requires that the textual (legalese) specification of the contract be accompanied by a precise computational definition of the actions leading to its satisfaction or breach, as well as of their admissible sequences. Insofar as contracts can be viewed as prescribing transactional exchanges of well-specified resources among well-specified actors, contract execution can be modelled as following some protocol in a closed world. This suggests a modelling of such executions as interactive processes in reaction systems, where the entities in the background set represent possible allocations of resources to actors and reactions describe changes in such allocations. We use this type of reaction systems and interactive processes as a basis for the modelling of transactions and contracts and explore properties of such processes, highlighting their peculiarities with respect to the original notion of interactive processes in reaction systems. We also discuss several constructions for composition and decomposition of processes, which guarantee equivalence of effects: two interactive processes are equivalent if, starting from the same initial set of allocations, they produce the same final set of allocations. (C) 2021 Elsevier B.V. All rights reserved
A dataflow platform for applications based on Linked Data
No full textModern software applications increasingly benefit from accessing the multifarious and heterogeneous Web of Data, thanks to the use of web APIs and Linked Data principles. In previous work, the authors proposed a platform to develop applications consuming Linked Data in a declarative and modular way. This paper describes in detail the functional language the platform gives access to, which is based on SPARQL (the standard query language for Linked Data) and on the dataflow paradigm. The language features interactive and meta-programming capabilities so that complex modules/applications can be developed. By adopting a declarative style, it favours the development of modules that can be reused in various specific execution contexts
A compositional view of derivations as interactive processes with applications to regulated and distributed rewriting
No full textThe derivation process in rewriting systems, especially in Chomskyan grammars, can be seen as consisting of four stages: (1) selection of the production to apply from a supply of productions available at that step, (2) check of applicability of the production, possibly on different matches, (3) selection of the match at which to apply the production, (4) actual application. In this paper, we explore the different ways in which models of regulated and distributed rewriting have extended these four basic mechanisms and we propose a unifying perspective on them in terms of interaction between two agents, expressed through a particular form of conditional rewriting systems. This introduces a compositional view of derivation processes, where different components, playing specific roles and exhibiting specific behaviours, can be made to communicate and combined into different models of derivation. Existing models of regulated and distributed rewriting can thus be reformulated in this new framework, and new ones can be obtained
Analyzing, Modelling, and Specifying Visual Interaction
No full textThis paper discusses the processes underlying human-computer visual interaction, thereby analysing the characteristics of visual interaction; a model and a theory of visual interaction, from which a formal specification of visual interactive systems that are trustable by their users can be derived, are also illustrated. Such a theory is called theory of visual sentences, since each message on the computer screen is described as a visual sentence, i.e., an element of a visual language that specifies the interaction. The concept of relational structure is introduced to take into account different kinds of relations which can exist among the characteristic patterns present in a visual sen- tence. A formal model of the dynamics of visual interac- tion is presented, which is specified as transformations of visual sentences, modelled through visual rewriting systems, and transformations of relational structures. Particular attention is given to usability issues so as to satisfy relevant features needed to allow non-ambiguity of interpretation, adequate communication, determinism and system viability. An example of visual interaction is given where an immunologist interacts with a simulation of the human immune system
Modular language product lines: concept, tool and analysis
No full textModelling languages are intensively used in paradigms like model-driven engineering to automate all tasks of the development process. These languages may have variants, in which case the need arises to deal with language families rather than with individual languages. However, specifying the syntax and semantics of each language variant separately in an enumerative way is costly, hinders reuse across variants, and may yield inconsistent semantics between variants. Hence, we propose a novel, modular and compositional approach to describing product lines of modelling languages. It enables the incremental definition of language families by means of modules comprising meta-model fragments, graph transformation rules, and rule extensions. Language variants are configured by selecting the desired modules, which entails the composition of a language meta-model and a set of rules defining its semantics. This paper describes: a theory for checking well-formedness, instantiability, and consistent semantics of all languages within the family; an implementation as an Eclipse plugin; and an evaluation reporting drastic specification size and analysis time reduction in comparison to an enumerative approach
Metareasoning as a tool for pattern recognition
No full textThe paper introduces the concepts of image interpretation by form feature and interpretation strategy as a fall out of observing human interpreters at work. It discusses the need for flexible control in an automatic interpreter, outlining an automatic interpretation process and the required meta (or reflective) mechanisms
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