The design of mashup tools combines elements from enduser development and software composition in the context of the Web. The challenge for mashup tool designers is to provide end-users with suitable abstractions, programming models and tool support for easily composing mashups out of existing Web services and Web data sources. In this paper we describe the design of a natural mashup composition environment based on the EnglishMash controlled natural language. The environment proactively

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... s users as they are learning the syntax of the EnglishMash language with features such as auto-completion, immediate feedback, live preview of the mashup execution and component discovery and selection based on natural language descriptions.