SSONDE: Semantic Similarity On liNked Data Entities

Linked data offers a promising setting to encode, publish and share metadata of resources. As the matter of fact, it is already adopted by data producers such as European Environment Agency, US and some EU Governs, whose first ambition is to share (meta)data making their processes more effective and transparent. Such as an increasing interest and involvement of data providers surely represents a genuine witness of the web of data success, but in a longer perspective, frameworks supporting linked data consumers in their decision making processes will be a compelling need. In this respect, the talk is introducing SSONDE, a framework enabling in detailed comparison, ranking and selection of linked data resources through the analysis of their RDF ontology driven metadata. SSONDE implements an instance similarity especially designed to support in resource selection, namely the process stakeholders engage to choose a set of resources suitable for a given analysis purpose: (i) it deploys an asymmetric similarity assessment to emphasize information about gains and losses the stakeholders get adopting a resource in place of another; (ii) it relies on an explicit formalization of contexts to tailor the similarity assessment with respect to specific user-defined selection goals. The talk aims at providing an insight on SSONDE instance similarity and it will briefly describe some examples of SSONDE deployment in the context of linked data consumption

Cathode Processes in MPD Thrusters

Magnetoplasmadynamic (MPD) thrusters have demonstrated performance and power handling capabilities which make them attractive for use on thrust-intensive and high energy missions, such as Earth to Mars transfer of a cargo vehicle or a crewed Mars mission. However, the performance and lifetime demonstrated so far with gaseous propellants are at best marginal for these missions. Thermionic cathodes have been long identified as the run-time limiting components in both steady-state and pulsed devices making them a priority in the development of future high power MPD thrusters. In this dissertation, an experimental and theoretical investigation of high-current hollow cathodes performance is carried out to provide guidelines for scaling and increasing MPDT lifetime. It is found that, whether the cathode technology, quasi-steady application results in erosion rates not compatible with any real mission duration. As a consequence, a theoretical model is derived for the performance evaluation of steady-state thermionic cathodes and verified by comparison with experimental data available in the literature. The model includes the effect of non-equilibrium multi-step ionization and allows for estimation of the plasma penetration length. It is shown that the cathode operative temperature can be effectively reduced by using low-work function refractory ceramics or by seeding the gaseous propellant with alkali metal vapours. However, since the seed neutral number densities required for an effective covering of the surface are in the order of the propellant density or higher, an emitting layer can be maintained only at very high seed mass flow rates. It is thus concluded that the use of non-diffusing low-work function insert is preferred. The physical insights obtained from this study can aid in defining design criteria and general guidelines for high-current hollow cathode design and performance evaluation

D-CaseLP: un ambiente distribuito per l\u27integrazione di Agenti Eterogenei.

It concerns the design of a rapid prototyping environment to ease the development of Multi-Agent Systems taking into account the declarative properties of logic programming paradigm and FIPA specification

Semantic and Visual Analysis of Metadata to Search and Select Heterogeneous Information Resources

An increasing number of activities in several disciplinary and industrial fields such as the scientific research, the industrial design and the environmental management, rely on the production and employment of informative resources representing objects, information and knowledge. The vast availability of digitalized information resources (documents, images, maps, videos, 3D model) highlights the need for appropriate methods to effectively share and employ all these resources. In particular, tools to search and select information resources produced by third parties are required to successfully achieve our daily work activities. Headway in this direction is made adopting the metadata, a description of the most relevant features characterizing the information resources. However, a plenty of features have to be considered to fully describe the information resources in sophisticated fields as those mentioned. This brings to a complexity of metadata and to a growing need for tools which face with this complexity. The thesis aims at developing methods to analyze metadata easing the search and comparison of information resources. The goal is to select the resources which best fit the user\u27s needs in specific activities. In particular, the thesis faces with the problem of metadata complexity and supports in the discovery of selection criteria which are unknown to the user. The metadata analysis consists of two approaches: visual and semantic analysis. The visual analysis involves the user as much as possible to let him discover the most suitable selection criteria. The semantic analysis supports in the browsing and selection of information resources taking into account the user\u27s knowledge which is properly formalized

Semantic Similarity Tailored on the Application Context

The paper proposes an approach to assess the semantic similarity among instances of an ontology. It aims to define a sensitive measurement of semantic similarity, which takes into account different hints hidden in the ontology definition and explicitly considers the application context. The similarity measurement is computed by analyzing, combining and extending some of the existing similarity measures and tailoring them according to the criteria induced by specific application context

Visualization and ontology to analyse categorical attributes in geographic metadata

No abstract availabl

Visualization of semantic similarity

No abstract availabl