What's up LOD Cloud? Observing The State of Linked Open Data Cloud Metadata

Linked Open Data (LOD) has emerged as one of the largest collections of interlinked datasets on the web. In order to benefit from this mine of data, one needs to access descriptive information about each dataset (or metadata). However, the heterogeneous nature of data sources reflects directly on the data quality as these sources often contain inconsistent as well as misinterpreted and incomplete metadata information. Considering the significant variation in size, the languages used and the freshness of the data, one realizes that finding useful datasets without prior knowledge is increasingly complicated. We have developed Roomba, a tool that enables to validate, correct and generate dataset metadata. In this paper, we present the results of running this tool on parts of the LOD cloud accessible via the datahub.io API. The results demonstrate that the general state of the datasets needs more attention as most of them suffers from bad quality metadata and lacking some informative metrics that are needed to facilitate dataset search. We also show that the automatic corrections done by Roomba increase the overall quality of the datasets metadata and we highlight the need for manual efforts to correct some important missing information.