A query can be assembled from one or more fragments called modules. [Definition: A module is a fragment of XQuery code that conforms to the Module grammar and can independently undergo the static analysis phase described in 2.3.3 Expression Processing. Each module is either a main module or a library module.]
[Definition: A main module consists of a Prolog followed by a Query Body.] A query has exactly one main module. In a main module, the Query Body is evaluated with respect to the static and dynamic contexts of the main module in which it is found, and its value is the result of the query.
[Definition: A module that does not contain a Query Body is called a library module. A library module consists of a module declaration followed by a Prolog.] A library module cannot be evaluated directly; instead, it provides function and variable declarations that can be imported into other modules.
The XQuery syntax does not allow a module to contain both a module declaration and a Query Body.
[Definition: A Prolog is a series of declarations and imports that define the processing environment for the module that contains the Prolog.] Each declaration or import is followed by a semicolon. A Prolog is organized into two parts.
The first part of the Prolog consists of setters, imports, namespace declarations, and default namespace declarations. [Definition: Setters are declarations that set the value of some property that affects query processing, such as construction mode or default collation.] Namespace declarations and default namespace declarations affect the interpretation of lexical QNames within the query. Imports are used to import definitions from schemas and modules. [Definition: The target namespace of a module is the namespace of the objects (such as elements or functions) that it defines. ]
The second part of the Prolog consists of declarations of variables, functions, and options. These declarations appear at the end of the Prolog because they may be affected by declarations and imports in the first part of the Prolog.
[Definition: The Query Body, if present, consists of an expression that defines the result of the query.] Evaluation of expressions is described in 4 Expressions. A module can be evaluated only if it has a Query Body.
Although item type declarations, as described in 5.19 Item Type Declarations, can be used to give names to record types as well as any other item type, named record types as described in this section provide a more concise syntax, plus additional functionality. In particular:
Named record types can be recursive.
Named record types implicitly create a constructor function that can be used to create instances of the record type.
A field in a named record type can be a function that has implicit access to the record on which it is defined, rather like methods in object-oriented languages.
The syntax is as follows:
A named record declaration serves as both a named item type and as a function definition, and it therefore inherits rules from both these roles. In particular:
Its name must not be the same as the name of any other named item type, or any generalized atomic type, that is present in the same static context [err:XQST0048].
If the declaration appearsis public and is within a library module, then its name must be in the target namespace of the library module [err:XQST0048].
As a function, it must not have an arity range that overlaps the arity range of any other function declaration having the same name in the same static context.
The order of field declarations is significant, because it determines the order of arguments in a call to the constructor function.
The fields must have distinct names. [err:XPST0021]
In order to work as both a record type and a function declaration, the names of the fields must be simple NCNames in no namespace; the names must not be written as string literals [err:XPST0003].
Note:
This is described here as a semantic constraint, but an implementation might choose to impose it at the level of the grammar.
If an initializing expression is present in an ExtendedFieldDeclaration, it must follow the rules for the initializing expression of a parameter in a function declaration, given in 5.18.3 Function Parameters. In particular, if any field has an initializing expression then all following fields must have an initializing expression.
Any annotations that are present, such as %public or %private, apply both to the item type declaration and to the function declaration.