which are interpreted as arguments. The element is a generic extension element that means whatever is specified in the content dictionary referred to in the attribute (this document can be found at the URI specified in the innermost attribute dominating the respective element. In the example above, all symbols come from the content dictionary for arithmetics (, see below), except for the , which comes from a non-standard place, hence the attribute here. OpenMath Content Dictionaries Content Dictionaries are structured XML documents that define mathematical symbols that can be referred to by OMS elements in OpenMath Objects. The OpenMath 2 standard does not prescribe a canonical encoding for content dictionaries, but only requires an infrastructure sufficient for unique referencing in OMS elements. OpenMath provides a very basic XML encoding that meets these requirements, and a set of specific content dictionaries for some areas of mathematics, in particular covering the K-14 fragment covered by content MathML. For more richly structured content dictionaries (and generally for arbitrary mathematical documents) the OMDoc format extends OpenMath by a “statement level” (including structures like definitions, theorems, proofs and examples, as well as means for interrelating them) and a “theory level”, where a theory is a collection of several contextually related statements. OMDoc's theories are designed to be compatible to OpenMath content dictionaries, but they can also be set into inheritance and import relations. Criticism OpenMath is criticised for being inadequate for general mathematics, exposing not enough formal precision to capture the intricacies of numerics, lacking a proof-of-concept and as an inferior technology to already established approaches of encoding mathematical semantics, amongst other presumed shortcomings. See also List of document markup languages Comparison of document markup languages MathML OMDoc TeX References External links Standard definition Content Dictionaries Markup languages Mathematical markup languages XML-based standards