We present an intelligent NLI interface, namely Quelo NLI, for querying and exploring semantic data. Its intelligence lies in the use of reasoning services over an ontology. These support the intentional navigation of the underlying datasource and the formulation of queries that are consistent with respect to it. Its Natural Language Generation (NLG) module masks the formulation of queries as the composition of English text and generates descriptions of query answers. An important feature of Quelo NLI is that it is portable as it is not bound to an ontology of a specific domain. We describe Quelo NLI functionality and present a grammar-based natural language generation approach that better supports the domain-independent generation of fluent queries and naturally extends for the generation of answers descriptions. We concentrate on describing the generation resources, namely a domain-independent hand-written grammar and a lexicon that is automatically extracted from concepts and relations of the underlying ontology.