MashQL: A Query-by-Diagram Language Technical Article Mustafa Jarrar University of Cyprus mjarrar@cs.ucy.ac.cy Marios D. Dikaiakos University of Cyprus mdd@cs.ucy.ac.cy ABSTRACT This article is motivated by the massively increasing structured data on the web (data web), and the need for novel methods to expose this data to its full potential. Building on the remarkable success of Web 2.0 mashups, and specially Yahoo Pipes, we generalize the idea of mashups and regard the Internet as a database. Each internet data source is seen as a table, and a mashup is seen as a query on these tables. We assume that web data sources are represented in RDF, and SPARQL is the query language. We propose a mashup language, called MashQL, which allows people to mash up data intuitively. In the background, MashQL queries are translated into and executed as SPARQL queries. The novelty of MashQL is that it allows one to query (and navigate) an RDF graph without any prior knowledge about its structure or technical details; as well as it supports pipelines and materialized queries as built-in concepts. Users also do not need any knowledge about RDF/SPARQL to get started. Although we focus on RDF/SPARQL mashups, but our approach can be easily reused for other data formats and query languages. Keywords Query-by-diagram, Query Formulation, Data Mashup, Semantic Mashup, Semantic Web, Data Web, Linked Data, Web 2.0 Table of Contents 1. Background and Motivation ........................ 1 2. Related Work and Contributions ................. 3 3. The Basics of MashQL.................................. 4 4. Formal Definition of MashQL ...................... 5 5. Query Pipelines ........................................... 8 6. Implementation........................................... 8 7. Use Cases................................................... 11 8. Discussion .................................................. 13 9. Evaluation.................................................. 14 Appendices ...................................................... 16 Remark: This is a live report, updated regularly (every week/month) to include our latest developments on all aspects related to MashQL (its formal syntax and semantics, implementation, use cases, evaluation, etc.). The content of this article is not published yet, thus if you wish to cite this work, please use the reference below. Any publication stemming from this report will be listed here. Reference: Jarrar M, Dikaiakos M: MashQL: A query-by-diagram. Technical Article TAR200805. University of Cyprus, 2008 Download from: http://www.jarrar.info/mashql/TA/