The Callimachus project: RDFa as a web template language

Abstract

Abstract. The uptake of semantic technology depends on the availability of simple tools that enable Web developers to build complete applications, with particular emphasis on the last mile, the user interface. RDFa is a vocabulary for adding semantic annotations to standard XHTML and HTML5 documents. This allows the page to contain machine-readable content that is easier to find and mashable with other content. This paper describes Callimachus, an Open Source project that turns this idea around, using RDFa as a template language for the bulk generation of human-readable Web pages from machine-readable RDF data. Most existing template engines generate Web pages by combining the template with query results from a relational database. In the Callimachus template engine, XHTML+RDFa templates pass through an RDFa parser and are then compiled into SPARQL for evaluation against an RDF database. The result set is combined with the template to produce a Web page populated with RDF data, retaining the embedded RDFa. This paper evaluates the benefits and shortcomings of RDFa as a template language, and examines the relationship between Callimachus and the adoption of Web standards such as RDFa.