Codelists from the Metadata with Schema Extensions (mex) Namespace Codelists from the Metadata with Schema Extensions (mex) Namespace ISO TC211 Metadata Standards 1.1 2017-09-10 eng UTF-8 MD_DatatypeCode MD_DatatypeCode datatype of element or entity datatype of element or entity class class descriptor of a set of objects that share the same attributes, operations, methods, relationships, and behaviour descriptor of a set of objects that share the same attributes, operations, methods, relationships, and behaviour codelist codelist flexible enumeration useful for expressing a long list of values, can be extended flexible enumeration useful for expressing a long list of values, can be extended enumeration enumeration data type whose instances form a list of named literal values, not extendable data type whose instances form a list of named literal values, not extendable codelistElement codelistElement permissible value for a codelist or enumeration permissible value for a codelist or enumeration abstractClass abstractClass class that cannot be directly instantiated class that cannot be directly instantiated aggregateClass aggregateClass class that is composed of classes it is connected to by an aggregate relationship class that is composed of classes it is connected to by an aggregate relationship specifiedClass specifiedClass subclass that may be substituted for its superclass subclass that may be substituted for its superclass datatypeClass datatypeClass class with few or no operations whose primary purpose is to hold the abstract state of another class for transmittal, storage, encoding or persistent storage class with few or no operations whose primary purpose is to hold the abstract state of another class for transmittal, storage, encoding or persistent storage interfaceClass interfaceClass named set of operations that characterize the behaviour of an element named set of operations that characterize the behaviour of an element unionClass unionClass class describing a selection of one of the specified types class describing a selection of one of the specified types metaClass metaClass class whose instances are classes class whose instances are classes typeClass typeClass class used for specification of a domain of instances (objects), together with the operations applicable to the objects. A type may have attributes and associations class used for specification of a domain of instances (objects), together with the operations applicable to the objects. A type may have attributes and associations characterString characterString textual information textual information integer integer numerical field numerical field association association semantic relationship between two classes that involves connections among their instances semantic relationship between two classes that involves connections among their instances MD_ObligationCode MD_ObligationCode obligation of the element or entity obligation of the element or entity mandatory mandatory element is always required element is always required optional optional element is not required element is not required conditional conditional element is required when a specific condition is met element is required when a specific condition is met