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A Distributed Infrastructure for Metadata about Metadata: The HDMM Architectural Style and PORTAL-DOORS System

by Carl Taswell

Future Internet 2010, 2(2), 156-189; https://doi.org/10.3390/fi2020156 - 1 Jun 2010

Cited by 19 | Viewed by 14969

Abstract

Both the IRIS-DNS System and the PORTAL-DOORS System share a common architectural style for pervasive metadata networks that operate as distributed metadata management systems with hierarchical authorities for entity registering and attribute publishing. Hierarchical control of metadata redistribution throughout the registry-directory networks constitutes an essential characteristic of this architectural style called Hierarchically Distributed Mobile Metadata (HDMM) with its focus on moving the metadata for who what where as fast as possible from servers in response to requests from clients. The novel concept of multilevel metadata about metadata has also been defined for the PORTAL-DOORS System with the use of entity, record, infoset, representation and message metadata. Other new features implemented include the use of aliases, priorities and metaresources. Full article

(This article belongs to the Special Issue Metadata and Markup)

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Figure 1

Figure 1
Beacons of Gondor dramatize a metaphor for the advantages of hierarchical communication networks that enable search and discovery of a small item in a very large world. If everybody remains trapped under the clouds in isolated valleys everywhere and unable to see elsewhere, then how will we (or software agents) communicate with each other fast enough to find and reach unknown destinations, persons (or agents), and small pieces of information in a large world that grows ever larger all the time? Full article ">Figure 2
PORTAL-DOORS System Data Records: Resource metadata is registered and published by agents for search by users in the PORTAL-DOORS server networks. Semantic services here are defined as those using the RDF/OWL/SPARQL stack of technologies, whereas lexical services are defined as those using only character string processing, terminologies, or those XML technologies that do not require use of RDF triples. Fields within data records are considered required or permitted with respect to the schemas maintained by the root servers. The figure displays only the most important fields; for all fields, see the reference model implemented with XML Schemas. Full article ">Figure 3
PORTAL-DOORS System Server Network: PDS server networks with interacting clouds of NEXUS registrars, PORTAL registries, and DOORS directories. NEXUS servers may expose either the NEXUS registrar service for the separate design or the integrated set of NEXUS registrar, PORTAL registry, and DOORS directory services for the combined design. These resource metadata server networks for PORTAL registering of labels and tags and DOORS publishing of locations and descriptions are analogous to domain metadata server networks for IRIS registering of names and DNS publishing of addresses. Primary PORTAL registries may be established by an organization or person who maintains any local policies governing registration of resources at that particular primary PORTAL registry. Examples shown here (GeneScene, BrainWatch, ManRay) implement policies with a problem-oriented focus on their respective specialty domains. Specific criteria for registration are determined by the local schema of the PORTAL primary which must nevertheless comply with the global requirements of the PORTAL root in order to assure interoperability between different PORTAL primaries. Full article ">Figure 4
Resource representation: entity metadata is primary or Level 1 metadata about the entity itself, record metadata is secondary or Level 2 metadata about the Level 1 metadata, and infoset metadata is tertiary or Level 3 metadata about the Level 1 and Level 2 metadata; see also <a href="#sec5dot2-futureinternet-02-00156" class="html-sec">Section 5.2</a>. Full article ">Figure 5
Relational database model for NEXUS combined design server with integrated storage of both PORTAL and DOORS data record fields as a NEXUS data record. See <a href="#futureinternet-02-00156-f006" class="html-fig">Figure 6</a> for the administrative content of a NEXUS record. Full article ">Figure 6
Relational database model for the auxiliary and administrative support tables for system and agent management in relation to the main table for the NEXUS combined design server. See <a href="#futureinternet-02-00156-f005" class="html-fig">Figure 5</a> for the non-administrative content of a NEXUS record. Full article ">

Abstract

A plethora of enabling optical and wireless access-metro network technologies have been emerging that can be used to build future-proof bimodal fiber-wireless (FiWi) networks. Hybrid FiWi networks aim at providing wired and wireless quad-play services over the same infrastructure simultaneously and hold great promise to mitigate the digital divide and change the way we live and work by replacing commuting with teleworking. After overviewing enabling optical and wireless network technologies and their QoS provisioning techniques, we elaborate on enabling radio-over-fiber (RoF) and radio-and-fiber (R&F) technologies. We describe and investigate new QoS provisioning techniques for future FiWi networks, ranging from traffic class mapping, scheduling, and resource management to advanced aggregation techniques, congestion control, and layer-2 path selection algorithms. Full article

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Future Internet, Volume 2, Issue 2 (June 2010) – 3 articles , Pages 96-189

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