Structure Standards According to the Encyclopedia of Computer Science (see References), a data structure is a collection of data values, the relationships among them, and the functions or operations that can be applied to the data. A data structure standard defines such a collection in general terms, so that it is possible to determine whether a particular collection of data values is an instance. (There are differing definitions of structured data, semi-structured data, and unstructured data, and the industry has not yet reached consensus on them. Arguably, any collection of data values has some structure. How non-trivial that structure must be for the collection to qualify as structured or semi-structured is for debate.) There are generic data structure standards that can apply to any application domain, and domain-specific data structure standards that define data structures appropriate to specific application domains.