Many people doubt the value of XML Schemas (in the general sense, W3C XML Schemas, RELAX schemas, DTDs, DAML, OIL). It may be true that they are not useful for your problem domains, but that is not the same as saying that they are not useful. So I'm going to list some reasons that some form of schema is potentially useful to you. Before I start, I'm going to address a common complaint about schemas: "Schemas only validate the syntax and you still have to validate the semantics." The first problem with this argument is that it isn't really a logical complaint. Schemas only solve part of the problem. But solving part of the problem is better than solving none of it, isn't it? The argument also implies a shared definition of what is "syntactic" and what is "semantic." But there is no such definition. Arguably the key constrants in XML Schema are "semantic" checks. Schematron constraints are all expressions, even mathematical expressions: that sounds semantic. And then there are the schema languages that are explicitly designed to constrain the semantics: DAML and OWL. Schemas make dispute resolution easier Schemas lower the barrier to entry in standards validation Schemas simplify your code Schemas encourage best practices and data-type interoperability Schemas can drive software Schemas can drive authoring interfaces Schemas enhance security Schemas can check syntax and semantics