Dereferencing a URI returns a representation of the current state of the resource identified by that URI. But, on the Web representations of prior states of a resource are also available, for example, as resource versions in Content Management Systems or archival resources in Web Archives such as the Internet Archive. This paper introduces a resource versioning mechanism that is fully based on HTTP and uses datetime as a global version indicator. The approach allows "follow your nose" style navigation both from the current time-generic resource to associated time-specific version resources as well as among version resources. The proposed versioning mechanism is congruent with the Architecture of the World Wide Web, and is based on the Memento framework that extends HTTP with transparent content negotiation in the datetime dimension. The paper shows how the versioning approach applies to Linked Data, and by means of a demonstrator built for DBpedia, it also illustrates how it can be used to conduct a time-series analysis across versions of Linked Data descriptions.
There is a relationship between the described work and efforts that research the problem of provenance of Linked Data, specifically those provenance aspects concerned with the time intervals in which specific data is valid. For example, @cite_7 , is concerned with provenance graphs that allow expressing such validity information, whereas @cite_8 focuses on applications to support preserving link integrity over time. Our proposal introduces a native HTTP approach that allows leveraging the results of these efforts at Web scale.
@cite_7 @cite_8
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The openness of the Web and the ease to combine linked data from dierent sources creates new challenges. Systems that consume linked data must evaluate quality and trustworthiness of the data. A common approach for data quality assessment is the analysis of provenance information. For this reason, this paper discusses provenance of data on the Web and proposes a suitable provenance model. While traditional provenance research usually addresses the creation of data, our provenance model also represents data access, a dimension of provenance that is particularly relevant in the context of Web data. Based on our model we identify options to obtain provenance information and we raise open questions concerning the publication of provenance-related metadata for linked data on the Web. The Linking Open Data (LOD) initiative has motivated numerous institutions to publish their data on the Web and to interlink them with those of other data sources. But since LOD sources are subject to change, links between resources can break and lead to processing errors in applications that consume linked data. The current practice is to ignore this problem and leave it to the applications what to do when broken links are detected. We believe, however, that LOD data sources should provide the highest possible degree of link integrity in order to relieve applications from this issue, similar to databases that provide mechanisms to preserve referential integrity in their data. As a possible solution, we propose DSNotify, an add-on for LOD sources that detects broken links and assists the data source in fixing them, e.g., when resources were moved to other Web locations.