Web applications frequently leverage resources made available by remote web servers. As resources are created, updated, deleted, or moved, these applications face challenges to remain in lockstep with the server's change dynamics. Several approaches exist to help meet this challenge for use cases where "good enough" synchronization is acceptable. But when strict resource coverage or low synchronization latency is required, commonly accepted Web-based solutions remain elusive. This paper details characteristics of an approach that aims at decreasing synchronization latency while maintaining desired levels of accuracy. The approach builds on pushing change notifications and pulling changed resources and it is explored with an experiment based on a DBpedia Live instance.
The Event Notification Protocol @cite_6 specifies requirements for change notifications in relation to WebDAV implementations. introduced by Popitsch and Haslhofer @cite_2 is a change detection and notification framework for Linked Datasets. @cite_20 introduced , a linking framework based on the Web of Data Link Maintenance Protocol http: www4.wiwiss.fu-berlin.de bizer silk wodlmp . Ping the Semantic Web http: pingthesemanticweb.com offers change notification as a web service. All three systems are geared towards Linked Datasets and are not designed as generic resource synchronization frameworks. They further rely on aggregated baseline data to be available in a central service, raising scalability concerns in light of an ever expanding Linked Data cloud. and its extension @cite_17 both provide a lightweight notification approach. However, the approaches are based on subscriptions to individual resources, making them problematic for large resource collections. The HTTP-based Simple Update Protocol (SUP) http: code.google.com p simpleupdateprotocol and the UDP-based Simple Lightweight Announcement Protocol (SLAP) http: joecascio.net joecblog 2009 05 18 announcing-slap provide conceptual mechanisms to notify about change events. However, they both suffer from the lack of acceptance and reference implementations.
@cite_20 @cite_17 @cite_6 @cite_2
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The Web of Data is built upon two simple ideas: Employ the RDF data model to publish structured data on the Web and to create explicit data links between entities within different data sources. This paper presents the Silk --- Linking Framework, a toolkit for discovering and maintaining data links between Web data sources. Silk consists of three components: 1. A link discovery engine, which computes links between data sources based on a declarative specification of the conditions that entities must fulfill in order to be interlinked; 2. A tool for evaluating the generated data links in order to fine-tune the linking specification; 3. A protocol for maintaining data links between continuously changing data sources. The protocol allows data sources to exchange both linksets as well as detailed change information and enables continuous link recomputation. The interplay of all the components is demonstrated within a life science use case. In this paper we tackle some pressing obstacles of the emerging Linked Data Web, namely the quality, timeliness and coherence of data, which are prerequisites in order to provide direct end user benefits. We present an approach for complementing the Linked Data Web with a social dimension by extending the well-known Pingback mechanism, which is a technological cornerstone of the blogosphere, towards a Semantic Pingback. It is based on the advertising of an RPC service for propagating typed RDF links between Data Web resources. Semantic Pingback is downwards compatible with conventional Pingback implementations, thus allowing to connect and interlink resources on the Social Web with resources on the Data Web. We demonstrate its usefulness by showcasing use cases of the Semantic Pingback implementations in the semantic wiki OntoWiki and the Linked Data interface for database-backed Web applications Triplify. The Web of Data has emerged as a way of exposing structured linked data on the Web. It builds on the central building blocks of the Web (URIs, HTTP) and benefits from its simplicity and wide-spread adoption. It does, however, also inherit the unresolved issues such as the broken link problem. Broken links constitute a major challenge for actors consuming Linked Data as they require them to deal with reduced accessibility of data. We believe that the broken link problem is a major threat to the whole Web of Data idea and that both Linked Data consumers and providers will require solutions that deal with this problem. Since no general solutions for fixing such links in the Web of Data have emerged, we make three contributions into this direction: first, we provide a concise definition of the broken link problem and a comprehensive analysis of existing approaches. Second, we present DSNotify, a generic framework able to assist human and machine actors in fixing broken links. It uses heuristic feature comparison and employs a time-interval-based blocking technique for the underlying instance matching problem. Third, we derived benchmark datasets from knowledge bases such as DBpedia and evaluated the effectiveness of our approach with respect to the broken link problem. Our results show the feasibility of a time-interval-based blocking approach for systems that aim at detecting and fixing broken links in the Web of Data.