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Bug 29963 - [FO31] Relation item type vs list types
Summary: [FO31] Relation item type vs list types
Alias: None
Product: XPath / XQuery / XSLT
Classification: Unclassified
Component: Functions and Operators 3.1 (show other bugs)
Version: Candidate Recommendation
Hardware: PC Windows NT
: P2 normal
Target Milestone: ---
Assignee: Michael Kay
QA Contact: Mailing list for public feedback on specs from XSL and XML Query WGs
Depends on:
Reported: 2016-10-30 15:40 UTC by Abel Braaksma
Modified: 2016-12-16 19:55 UTC (History)
1 user (show)

See Also:


Description Abel Braaksma 2016-10-30 15:40:25 UTC
(part of the series of issues on FO31 review)

The section 1.6 on the type system does not make clear what the relation is between item and list types. In particular, the first diagram starts with item, and has xs:anyAtomicType as a descendant. The second diagram also has xs:anyAtomicType in it, with xs:anySimpleType as parent.

You may deduce from this that item == xs:anySimpleType, or more indirectly, item is a parent (and therefore an instance of) list types, but I doubt that is the intent.

I have to admit I am not sure how this could be drawn differently, perhaps a note that explains the relation between diagram 1 and 2 better?
Comment 1 Michael Kay 2016-10-30 18:19:03 UTC
F+O merely copies these diagrams from the Data Model spec.

There is no relation between item types and list types, other than the fact that both (unfortunately) use the same word "type" in their names. Item types fit into the hierarchy rooted at item(), which is defined in XDM, while list types fit into the hierarchy rooted at xs:anyType, which is defined in XSD. Comparing the two is a category error.

We've made good progress in separating the concepts since XDM 1.0, which attempted to show both hierarchies on a single diagram.
Comment 2 Michael Kay 2016-10-31 23:30:26 UTC
Reclassified as F+O 3.1.
Comment 3 Josh Spiegel 2016-11-01 15:35:05 UTC
The introduction sentence calls out that the type system comprises two distinct subsystems that both include primitive atomic types.  Mike will try to restructure the section to help clarify this.  I am closing the bug but feel free to reopen with suggestions on further clarifications that you think would be helpful.
Comment 4 Abel Braaksma 2016-11-01 16:11:15 UTC
Seems reasonable, tx.