Flexible querying of semi-structured information

In order to inquiry semistructured information the need of flexible query languages has soon emerged. In the context of semistructured databases, by flexible query languages it is substantially meant languages that take into account the lack of a rigid schema of the database, thus allowing to enquiry both data and the type/schema. We consider the problem of defining flexible query languages for inquiring XML documents. In particular, the use of fuzzy set theory to define flexible query languages to the aim of expressing soft selection conditions on both the documents' structure and contents is presented.