Section 20: refer to rules in OData ABNF Construction Rules that define the necessary literals, add ABNF rules if necessary

The stand-in subsections PathString, xsBoolean, xsDateTime, xsDecimal, xsDouble, xsGuid, xsHexBinary, xsInteger, and xsString are only referred once, so defining the terms in-place increases readability. The xsXxx terms can be defined by referring to the corresponding xs:xxx sections in XML Schema, Part 2, which is a normative reference anyway. xsTime needs further discussion, see ODATA-70 Proposed new content of section 20: 20 Attribute Values 20.1 Namespace A Namespace is a character sequence conforming to the rule namespace in [OData-ABNF] .Non-normatively speaking it is a dot-separated sequence of SimpleIdentifiers. 20.2 SimpleIdentifier A SimpleIdentifier is a character sequence conforming to rule odataIdentifier in [OData-ABNF] . Non-normatively speaking it starts with a letter or underscore, followed by at most 478 letters, underscores or digits. 20.3 QualifiedName For model elements that are direct children of a schema: the namespace or alias of the schema that defines the model element, followed by a dot and the name of the model element, see rule XXX in [OData-ABNF] . For model elements that are direct children of an entity container: the simple or qualified name of the entity container, followed by a dot and the name of the model element, see rule XXX in [OData-ABNF] . 20.4 AnyTypeName The simple or qualified name of a primitive type, complex type, enumeration type, or entity type, or a collection of one of these types, see rule qualifiedTypeName in [OData-ABNF] . The type must be in scope, i.e. if a SimpleIdentifier is used, the type MUST be defined in the same schema, and if a QualifiedName is used, the type MUST be defined in the schema identified by the namespace or alias portion of the qualified name, and the identified schema MUST have been imported with edm:Using. 20.5 AnySingleTypeName The simple or qualified name of a primitive type, complex type, enumeration type, or entity type in scope. 20.6 AnyKeylessTypeName The simple or qualified name of a primitive type, complex type, or enumeration type in scope, or a collection of one of these types. 20.7 SingleEntityTypeName The simple or qualified name of an entity type in scope. 20.8 Boolean One of the literals true and false.