SPARQL queries are a great way to explore Linked Data sets - be it our STW with it's links to other vocabularies, the papers of our repository EconStor, or persons or institutions in economics as authority data. ZBW therefore offers since a long time public endpoints. Yet, it is often not so easy to figure out the right queries. The classes and properties used in the data sets are unknown, and the overall structure requires some exploration. Therefore, we have started collecting queries in our new SPARQL Lab, which are in use at ZBW, and which could serve as examples to deal with our datasets for others.
A major challenge was to publish queries in a way that allows not only their execution, but also their modification by users. The first approach to this was pre-filled HTML forms (e.g. http://zbw.eu/beta/sparql/stw.html). Yet that couples the query code with that of the HTML page, and with a hard-coded endpoint address. It does not scale to multiple queries on a diversity of endpoints, and it is difficult to test and to keep in sync with changes in the data sets. Besides, offering a simple text area without any editing support makes it quite hard for users to adapt a query to their needs.
- SPARQL syntax highlighting and error checking
- Extremely customizable: All functions and handlers from the CodeMirror library are accessible
- Persistent values (optional): your query is stored for easier reuse between browser sessions
- Prefix autocompletion (using prefix.cc)
- Property and class autocompletion (using the Linked Open Vocabularies API)
- Can handle any valid SPARQL resultset format
- Integration of preflabel.org for fetching URI labels
With a few lines of custom clue code, and with the friendly support of Laurens Rietveld, author of the YASGUI suite, it is now possible to load any query stored on GitHub into an instance on our beta site and execute it. Check it out - the URI
loads, views and executes the query stored at https://github.com/jneubert/sparql-queries/blob/master/class_overview.rq on the endpoint
http://data.nobelprize.org/sparql (which is CORS enabled - a requirement for queryRef to work).
Links like this, with descriptions of query's purpose, grouped according to tasks and datasets, and ordered in a sensible way, may provide a much more accessible repository and starting point for explorations than just a directory listing of query files. For ongoing or finished research projects, such a repository - together with versioned data sets deployed on SPARQL endpoints - may offer a easy-to-follow and traceable way to verify presented results. GitHub provides an infrastructure for publicly sharing the version history, and makes contributions easy: Changes and improvements to the published queries can be proposed and integrated via pull requests, an issue queue can handle bugs and suggestions. Links to queries authored by contributors, which may be saved in different repositories and project contexts, can be added straightaway. We would be very happy to include such contributions - please let us know.