Archive for June, 2007

Scanning Slides

Sunday, June 24th, 2007



Scanning Slides

Originally uploaded by abdelazer

I spent most of the weekend (a couple of weekends ago now) scanning my old slides on a rented Nikon 35mm scanner (rented happily from Pro Camera Rental). Working on my photographs (mainly from my digital P+S) in Lightroom during the recent months has reawakened my interest in photography, so I’m hoping that I can find some good images to work on from older slides I’ve taken.

The scanner itself, a Nikon Coolscan IV, produced very high quality TIFFs (64MB/slide) but was quite slow. My final average scanning rate was about 20 slides an hour.

DocBook-XSL Sytlesheets have >600 Parameters

Wednesday, June 13th, 2007

Norm Walsh writes:

Stylesheets can have literally hundreds of parameters. The DocBook XSL Stylesheets have more than six hundred.

All I can say at this point is: wow. Grepping the core of our own customization shows 121 <xsl:param>s (about 20 of which we introduced) and 52 <xsl:attribute-set>s (20, again). Thinking about it now (as I haven’t before), we’ve probably minimized that number by completely overriding 13 of the “regular” fo/ stylesheets directly (rather than using params or smaller, single-template overrides). The DocBook-XSL sytlesheets are a truly impressive, complex project.

Their complexity brings me to the other DocBook-related news item from today, in which Bob DuCharme argues that XHTML 2:

will hit a sweet spot between the richness of DocBook and the simplicity of XHTML 1

I’m certainly hopeful that our work in the DocBook SubCommittee for Publishers will move a subset of DocBook closer to that “sweet spot”.

Partial Updates: A Simpler Strawman?

Sunday, June 10th, 2007

James Snell has been working some interesting things as the work on the Atom Publishing Protocol spec winds down. Most recently, he posted some thoughts on how to effectively communicate partial updates to APP servers using HTTP PATCH.

[UPDATE: James points out the obvious drawback to this approach in his response.]

One of the things that surprised me when I met other APP implementors at the interop was the relative lack of concern they seemed to have about the actual content inside their <atom:entry>s. This may have simply been a simplification on their part for the sake of testing (“if it can accept a single line of XHTML div it can accept anything, essentially) rather than their real views, but to someone very concerned about perfect content fidelity, it sorta scared me. These tiny <atom:entry>s might hide the some of the problems that APP will face in the wild, particularly for document repositories.

Long before the interop, we’d decided internally at O’Reilly to use the Media Resources rather than the <atom:entry> container (in large part because of the size of our DocBook documents, often over 2MB) for our document repository implementation. Because of the larger size of our content blocks, the sort of partial updates that James is thinking about might be quite cool.

The core of James’ strawman is an XML delta syntax (with credit due to Andy Roberts‘ work on the same) for HTTP PATCH with 8 operations: insert-before, insert-after, insert-child, replace, remove, remove-all, set-attribute and remove-attribute. Coming at this problem with my experience in document transformation and XSLT, I saw 7 of those operations (everything but ‘replace’) as unnecessary. The basic inspiration is thinking about each operation as an XSLT template. Mentally translate the d:replace/@path into xsl:template/@match and swap the bodies and you’ll be with me (with luck!).

Here’s the specific rundown of the 7 operations other than ‘replace’ working with James’ simple example <atom:entry>:

 1 <?xml version="1.0"?>
 2 <entry xmlns="http://www.w3.org/2005/Atom">
 3   <id>http://example.org/foo/boo</id>
 4   <title>Test</title>
 5   <updated>2007-12-12T12:12:12Z</updated>
 6   <summary>Test summary</summary>
 7   <author>
 8     <name>James</name>
 9   </author>
10   <link href="http://example.org"/>
11 </entry>

Note: You’ll have to imagine these working on a much larger XML document than my examples to understand the importance.

insert-before

 1 PATCH /collection/entry/1 HTTP/1.1
 2 Host: example.org
 3 Content-Type: application/delta+xml
 4 Content-Length: nnnn
 5 
 6 <d:delta
 7   xmlns:d="http://purl.org/atompub/delta"
 8   xmlns="http://www.w3.org/2005/Atom"
 9   xmlns:atom="http://www.w3.org/2005/Atom"
10   xmlns:b="http://example.org/foo">
11 
12   <!-- substitute for insert-before
13        /atom:entry/atom:author/atom:name
14        an atom:email -->
15   <d:replace path="/atom:entry/atom:author">
16     <atom:author>
17       <atom:email>james@example.org</atom:email>
18       <atom:name>James</atom:name>
19     </atom:author>
20   </d:replace>
21 </d:delta>

insert-after

 1 PATCH /collection/entry/1 HTTP/1.1
 2 Host: example.org
 3 Content-Type: application/delta+xml
 4 Content-Length: nnnn
 5 
 6 <d:delta
 7   xmlns:d="http://purl.org/atompub/delta"
 8   xmlns="http://www.w3.org/2005/Atom"
 9   xmlns:atom="http://www.w3.org/2005/Atom"
10   xmlns:b="http://example.org/foo">
11 
12   <!-- substitute for insert-after
13        /atom:entry/atom:author/atom:name
14        an atom:uri -->
15   <d:replace path="/atom:entry/atom:author">
16     <atom:author>
17       <atom:name>James</atom:name>
18       <atom:uri>http://example.org/blogs/james</atom:uri>
19     </atom:author>
20   </d:replace>
21 </d:delta>

insert-child

 1 PATCH /collection/entry/1 HTTP/1.1
 2 Host: example.org
 3 Content-Type: application/delta+xml
 4 Content-Length: nnnn
 5 
 6 <d:delta
 7   xmlns:d="http://purl.org/atompub/delta"
 8   xmlns="http://www.w3.org/2005/Atom"
 9   xmlns:atom="http://www.w3.org/2005/Atom"
10   xmlns:b="http://example.org/foo">
11 
12   <!-- substitute for insert-child
13        /atom:entry/atom:author
14        an atom:uri -->
15   <d:replace path="/atom:entry/atom:author">
16     <atom:author>
17       <atom:name>James</atom:name>
18       <atom:uri>http://example.org/blogs/james</atom:uri>
19     </atom:author>
20   </d:replace>
21 </d:delta>

remove

 1 PATCH /collection/entry/1 HTTP/1.1
 2 Host: example.org
 3 Content-Type: application/delta+xml
 4 Content-Length: nnnn
 5 
 6 <d:delta
 7   xmlns:d="http://purl.org/atompub/delta"
 8   xmlns="http://www.w3.org/2005/Atom"
 9   xmlns:atom="http://www.w3.org/2005/Atom"
10   xmlns:b="http://example.org/foo">
11 
12   <!-- substitute for remove
13        /atom:entry/atom:author/atom:name -->
14   <d:replace path="/atom:entry/atom:author/atom:name">
15   </d:replace>
16   <!-- yeah, this no atom:author is longer valid ..-->
17 </d:delta>

remove-all

 1 PATCH /collection/entry/1 HTTP/1.1
 2 Host: example.org
 3 Content-Type: application/delta+xml
 4 Content-Length: nnnn
 5 
 6 <d:delta
 7   xmlns:d="http://purl.org/atompub/delta"
 8   xmlns="http://www.w3.org/2005/Atom"
 9   xmlns:atom="http://www.w3.org/2005/Atom"
10   xmlns:b="http://example.org/foo">
11 
12   <!-- substitute for remove
13        /atom:entry/atom:author/atom:name -->
14   <d:replace path="/atom:entry/*">
15   </d:replace>
16   <!-- yeah, this atom:entry is no longer valid ..-->
17 </d:delta>

set-attribute

 1 PATCH /collection/entry/1 HTTP/1.1
 2 Host: example.org
 3 Content-Type: application/delta+xml
 4 Content-Length: nnnn
 5 
 6 <d:delta
 7   xmlns:d="http://purl.org/atompub/delta"
 8   xmlns="http://www.w3.org/2005/Atom"
 9   xmlns:atom="http://www.w3.org/2005/Atom"
10   xmlns:b="http://example.org/foo">
11 
12   <!-- substitute for set-attribute
13        /atom:entry/atom:link/@href 
14        to http://not-example.org -->
15   <d:replace path="/atom:entry/atom:link/@href">http://not-example.org</d:replace>
16 </d:delta>

remove-attribute

 1 PATCH /collection/entry/1 HTTP/1.1
 2 Host: example.org
 3 Content-Type: application/delta+xml
 4 Content-Length: nnnn
 5 
 6 <d:delta
 7   xmlns:d="http://purl.org/atompub/delta"
 8   xmlns="http://www.w3.org/2005/Atom"
 9   xmlns:atom="http://www.w3.org/2005/Atom"
10   xmlns:b="http://example.org/foo">
11 
12   <!-- substitute for remove-attribute
13        /atom:entry/atom:link/@href -->
14   <d:replace path="/atom:entry/atom:link">
15     <atom:link/>
16   </d:replace>
17   <!-- you can't take the easy way and match
18        the attribute, because an empty attribute
19        (@attr="") means something different than
20        the absence of @attr -->
21   <!-- and this atom:link is longer valid ..-->
22 </d:delta>

I think the above could be fairly easily implemented as a transformation into either XQuery or XSLT, but I’d imagine that it could be implemented using streaming techniques as well. Thoughts?

JRuby + Jetty

Wednesday, June 6th, 2007

I finally figured out how to get JRuby to serve a Jetty servlet today (thanks to Charles). The key was flipping what I’d been trying to do for a while (getting Jetty to run JRuby). Here’s code that implements the AbstractHandler interface pretty trivially:

$ cat jetty_example.jrb
require 'java'
include_class 'javax.servlet.ServletException'
include_class 'javax.servlet.http.HttpServlet'
include_class 'javax.servlet.http.HttpServletRequest'
include_class 'javax.servlet.http.HttpServletResponse'

include_class 'org.mortbay.jetty.Server'
include_class 'org.mortbay.jetty.servlet.Context'
include_class 'org.mortbay.jetty.servlet.ServletHolder'
include_class 'org.mortbay.jetty.handler.AbstractHandler'

class SimpleHandler < AbstractHandler
  def handle(target, request, response, dispatch)
    response.setContentType("text/html")
    response.setStatus(HttpServletResponse::SC_OK)
    response.getWriter().println("<h1>Goodbye, cruel monoglot world!</h1>")
    request.setHandled(true)
  end
end

handler = SimpleHandler.new
server = Server.new(8080)
server.setHandler(handler)
server.start()

To run, add Jetty to your classpath:

$ export CLASSPATH="/path/to/jetty-6.1.3.jar:/.../jetty-util-6.1.3.jar:/.../servlet-api-2.5-6.1.3.jar"

Then it’s just a normal JRuby invocation:

$ jruby jetty_example.jrb

It’s trivial code at this point (and doesn’t handle concurrent requests, maxing out at 6.47r/s across my network), but at least it’s got me started.

[UPDATE: I can get the non-concurrent request handling way down with just a few simple tweaks (mainly running JRuby in SERVER mode) and running ab locally ;-)]