[MarkLogic Dev General] Bug in XCC - lone attributes reporting as elements.

[Danny Sokolsky]

Hi David,

Keep in mind that XML does not have a specified way of serializing an attribute node by itself, so any serialization of a plain attribute node is a little odd.  For example, I don't think any XML parser can deserialize a plain attribute node.

-Danny

From: general-bounces at developer.marklogic.com [mailto:general-bounces at developer.marklogic.com] On Behalf Of Lee, David
Sent: Monday, March 01, 2010 12:09 PM
To: General Mark Logic Developer Discussion
Subject: RE: [MarkLogic Dev General] Bug in XCC - lone attributes reporting as elements.

Thanks, this seems a problem in the XCC binary serialization.  This really needs improvement if XCC cant serialize arbitrary XDM values.

Unfortunately I can't use your suggestion as my use case is to run other-peoples-code ... so I cant require them to add extra stuff to it.
Well ... except that I'm telling them to run  fn:string() on attributes, but I'd like to handle *any XDM Type* returned from an XQuery.

FYI my use case is the marklogic extension to xmlsh

http://www.xmlsh.org/MarkLogic
In particular the query command where I dont have any ability to enforce special xquery code.

Thanks for your reply.

As a side note I'm slowly working on a proposal for XDM serialization which overlaps some of this issue... its a general case that many xquery processors dont actually handle XDM output like they should.

http://xml.calldei.com/XDMSerialize


-David


----------------------------------------
David A. Lee
Senior Principal Software Engineer
Epocrates, Inc.
dlee at epocrates.com<mailto:dlee at epocrates.com>
812-482-5224



From: general-bounces at developer.marklogic.com [mailto:general-bounces at developer.marklogic.com] On Behalf Of Sam Neth
Sent: Monday, March 01, 2010 2:59 PM
To: General Mark Logic Developer Discussion
Subject: Re: [MarkLogic Dev General] Bug in XCC - lone attributesreportingas elements.

Unfortunately the result sequence sent by the server simply doesn't contain this information; you might consider obtaining the type yourself, using the xdmp:node-kind builtin, and including that information in the result, possibly by wrapping a special element around attribute nodes:

xdmp:node-kind($x) = "attribute") then <attribute-node>{ $x }</attribute-node> else $x

This also has the benefit of making the attribute name available on the client.

On Mar 1, 2010, at 11:19 AM, Lee, David wrote:

Thanks !
In my use case, any kind of method to accurately determine the Xdm type of results would be good enough, even if full attribute (XdmAttribute) support wasnt implemented.  I I could only 'know' an item was an attribute then I can serialize it with the current implementation (I've tested
                ResultItem.writeTo( outputStream ) and it writes the value of the attribute just fine).

So just knowing the XDM type would be sufficient for me.

Thanks for noting this issue.

-David Lee




From: general-bounces at developer.marklogic.com<mailto:general-bounces at developer.marklogic.com> [mailto:general-bounces at developer.marklogic.com] On Behalf Of Sam Neth
Sent: Monday, March 01, 2010 1:51 PM
To: General Mark Logic Developer Discussion
Subject: Re: [MarkLogic Dev General] Bug in XCC - lone attributes reportingas elements.

This would be the appropriate place to report a bug or RFE, assuming no support contract is in place.  In this case, the behavior you describe is a known limitation of XCC which we are already tracking as an RFE.  You may consider your interest noted.

On Mar 1, 2010, at 5:46 AM, Lee, David wrote:


Whats the best way to report this bug ?

If I run an ad-hoc query in XCC which returns a single attribute, for example :
       attribute {"foo"} {"bar"}

The resulting item in XCC is reporting itself as an element, but (of course) wont serialize.
I would like to be able to detect lone attributes for special handling but I cant because XCC is incorrectly representing them as Elements

Example code  fragment:

  while (rs.hasNext()) {
     ResultItem rsItem = rs.next();


     ItemType type = rsItem.getItemType();
     XdmItem item = rsItem.getItem();
     if( (type.isNode() && item instanceof XdmAttribute)  )
                                // FAILS TEST ...  item is an ElementImpl not an XdmAttribute


---
item       ElementImpl  (id=62)
   stream               null
   stringVal           "bar" (id=73)
   type                    NodeType  (id=58)





----------------------------------------
David A. Lee
Senior Principal Software Engineer
Epocrates, Inc.
dlee at epocrates.com<mailto:dlee at epocrates.com>
812-482-5224

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