XML's flexible yet reliable structures have attracted a large number of data-oriented developers in addition to the document-oriented developers for whom XML was created. Database developers and programmers are using XML as a common medium for data interchange, using XML document structures to bridge different data storage and processing environments. While they share the foundations of XML with developers creating documents, the two groups often have different needs. Fortunately, XML is flexible enough to accommodate multiple uses, and extensions (like data typing) that strengthen its data handling capabilities are under development. In effect, XML provides a bridge between these two communities, letting them share information that used to be kept in completely different worlds.
Data-oriented schemas often represent internal data structures, like tables from relational databases and properties of objects. XML Instance can import data-oriented XML schemas. In some cases, data-oriented schemas provide a convenient middle ground between different applications, using a common format that all applications can read, but which may not actually reflect the internal structures of any of the applications using it.
Schemas representing data often overlap with content-oriented schemas, while schemas representing documents are more typically structure-oriented or presentation-oriented. One important capability of XML, supported by XML Instance, is that both types of information can be accommodated in a single schema, integrating documents and data. A document may contain tables filled with meaningful data; similarly, a document schema may contain areas that otherwise seem data-oriented. For document developers, a large part of XML's promise is its ability to store meaningful data inside of documents that can be reused by other applications. For developers working with data, a large part of XML's promise is that all kinds of data can be stored within these structures that were originally created for documents.
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