Status of this Document
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.
This document is governed by the 1 March 2017 W3C Process Document.
This is a Recommendation of the W3C. It was jointly developed by the W3C XML Query Working Group and the W3C XSLT Working Group, each of which is part of the XML Activity.
This Editor's Draft specifies the XQuery and XPath Data Model (XDM) version 4.0, a fully compatible extension of XDM version 3.1.
This specification is designed to be referenced normatively from other specifications defining a host language for it; it is not intended to be implemented outside a host language. The implementability of this specification has been tested in the context of its normative inclusion in host languages defined by the XQuery 3.1 and XSLT 3.0 specifications; see the XQuery 3.1 implementation report (and, in the future, the WGs expect that there will also be an XSLT 3.0 implementation report) for details.
No substantive changes have been made to this specification since its publication as a Proposed Recommendation.
Please report errors in this document using W3C's public Bugzilla system (instructions can be found at https://www.w3.org/XML/2005/04/qt-bugzilla). If access to that system is not feasible, you may send your comments to the W3C XSLT/XPath/XQuery public comments mailing list, public-qt-comments@w3.org. It will be very helpful if you include the string “[XDM31]” in the subject line of your report, whether made in Bugzilla or in email. Please use multiple Bugzilla entries (or, if necessary, multiple email messages) if you have more than one comment to make. Archives of the comments and responses are available at https://lists.w3.org/Archives/Public/public-qt-comments/.
This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.
This document was produced by groups operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures (W3C XML Query Working Group) and a public list of any patent disclosures (W3C XSLT Working Group) made in connection with the deliverables of each group; these pages also include instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
Dedication
The publications of this community group are dedicated to our co-chair, Michael Sperberg-McQueen (1954–2024).
This section outlines a number of general concepts that apply throughout this specification.
In this document, examples and material labeled as “Note” are provided for explanatory purposes and are not normative.
An important characteristic of the data model is that there is no distinction between an item (a node, function, or atomic item) and a singleton sequence containing that item. An item is equivalent to a singleton sequence containing that item and vice versa.
A sequence may contain any mixture of nodes, functions, and atomic items. When a node is added to a sequence its identity remains the same. Consequently a node may occur in more than one sequence and a sequence may contain duplicate items.
Sequences never contain other sequences; if sequences are combined, the result is always a “flattened” sequence. In other words, appending “(d e)” to “(a b c)” produces a sequence of length 5: “(a b c d e)”. It does not produce a sequence of length 4: “(a b c (d e))”; such a nested sequence never occurs.
Note:
Sequences replace node-sets from XPath 1.0. In XPath 1.0, node-sets do not contain duplicates. In generalizing node-sets to sequences, duplicate removal is provided by functions on node sequences.
Note:
Arrays and maps are function items and therefore can also be contained within sequences.
The following constructor and accessor functions are defined for sequences; these provide a formal underpinning for user-visible functions, operators, and language constructs.
2.6.4 iterate-sequence Accessor
dm:iterate-sequence( | $input | as array(*), |
$action | as function(item(), xs:integer) as item()*) as item()* |
The dm:iterate-sequence accessor calls the supplied $action function once for each item in $input, in order, and returns the sequence concenation of the results. The $action function is called with two arguments. The first argument is an item in $input, and the second is the 1-based ordinal position of the item within $input.The dm:iterate-sequence accessor calls the supplied $action function once for each item in $input, in order, and returns the sequence concatenation of the results. The $action function is called with two arguments. The first argument is an item in $input, and the second is the 1-based ordinal position of the item within $input.The dm:iterate-sequence accessor calls the supplied $action function once for each item in $input, in order, and returns the sequence concenationconcatenation of the results. The $action function is called with two arguments. The first argument is an item in $input, and the second is the 1-based ordinal position of the item within $input.
The function is exposed in XPath most directly through the function for-each, as well as for expressions in XPath, for clauses in FLWOR expressions in XQuery, and the xsl:for-each instruction in XSLT. It also underpins all other functions that manipulate sequences, such as fn:count and fn:filter.