τεχνοσοφια

As I mentioned earlier, I've been learning about linked data in the context of dropping it into the World Digital Library project. I am hopeful we'll be able to deploy the RDF views[1] before too long. In advance of that, I thought it might be helpful to share a sample of what our RDF would look like. The RDF below represents the WDL item for the U.S. Constitution. I appreciate constructive criticism.

A few things to note:

• Mmm, Unicode.
• Item types are from the Bibliographic Ontology.
• Most of the properties are from the Dublin Core Metadata Element Set ontology, especially used where literals are objects rather than resources identified by URI.
• Where possible I dug up or found URIs and used the Dublin Core Metadata Terms ontology.
• An item is modeled as an aggregation of its constituent files, as defined in OAI-ORE. The notion here is that an ORE aggregation of an item, as expressed in a resource map which is discoverable via a link header in each item detail page, is a "whole" item, including all of its files[2], metadata, and translations.
• I'm also making light use of the NEPOMUK File Ontology to express that constituent files are files, and to be explicit about file sizes so that folks know in advance of retrieving it how large files are.
• Links out to DDC (Decimalised Database of Concepts), Lingvoj, DBpedia, and Library of Congress Authorities & Vocabularies (e.g., LC Subject Headings) are included where possible. [3] I'd be especially stoked to hear of other vocabs I might link to. The more linked the data, the better.
• The output below is Turtle for readability, but the application will offer up RDF/XML.

The data after the jump:
Continue reading…

Notes

1. Sadly, the URIs are uglyish due to some constraints from our caching configuration. I figure we can redirect uglyish URIs to cool ones and make use of owl:sameAs if those constraints go away. [↩]
2. sans certain low-quality derivatives such as small thumbnails and tiles for the zoom interface [↩]
3. I was poking through the DBpedia output for Geonames URIs as well, but my method was way too slow and clunky, so that's disabled for the time being. Clients can always follow their noses from the DBpedia output. [↩]

I've been periodically poking at getting Linked Data/RDF views hooked into the World Digital Library web application, following Ed Summers' lead from his work on Chronicling America. The RDF views also use the OAI-ORE vocabulary to express aggregations — in WDL, an item is an aggregation of its constituent files. The goal is to provide a semantically rich and holistic representation of a WDL item (identifier, constituent files, metadata, translations, and so on).

The ORE format is a new one for me so it's hard to say whether the output of my dev branch is valid ORE or not. Plus I'm a sucker for validators. Turns out Rob Sanderson has developed a Python library for validating ORE, and this little snippet is what I've been using to validate the ORE. I didn't put much effort into making it readable, so much as banging something functional out so I can meet deadlines, so mea culpa and all that. But without further hemming and hawing, the code:

# validate.py
import sys
from foresite import *
 
rem = RdfLibParser().parse(ReMDocument(sys.argv[1]))
aggr = rem.aggregation
n3 = RdfLibSerializer('n3')
rem2 = aggr.register_serialization(n3)
print rem2.get_serialization(n3).data

Most of this code is naively copied and pasted from Rob's excellent Foresite documentation.

I invoke it thusly: python validate.py {URL}

And the output:

@prefix _27: <http://www.semanticdesktop.org/ontologies/nfo#>.
@prefix _28: <http://localhost/en/item/1/id#>.
@prefix _29: <http://localhost/en/item/1/>.
@prefix bibo: <http://purl.org/ontology/bibo/>.
@prefix dc: <http://purl.org/dc/elements/1.1/>.
@prefix dcterms: <http://purl.org/dc/terms/>.
@prefix ore: <http://www.openarchives.org/ore/terms/>.
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix rdfs1: <http://www.w3.org/2001/01/rdf-schema#>.
 
 _28:ResourceMap a ore:ResourceMap;
     dc:format "text/rdf+n3";
     dcterms:created "2009-07-31T14:23:31Z";
     dcterms:modified "2009-07-31T14:23:31Z";
     ore:describes _29:id. 
 
 _29:id a bibo:Image,
         ore:Aggregation;
     dcterms:DDC "973";
     dcterms:alternative "Antietam, Maryland. Allan Pinkerton, President Lincoln, and Major General John A. McClernand"@en;
     dcterms:created "1862年10月3日"@zh,
         "3 de octubre de 1862"@es,
         "3 de outubro de 1862"@pt,
         "3 octobre 1862"@fr,
         "3 октября 1862 года"@ru,
         "October 3, 1862"@en,
         " ٣ آكتوبر، ١٨٦٢"@ar;
     dcterms:creator "Gardner, Alexander"@en,
         "Gardner, Alexander"@es,
         "Gardner, Alexander"@fr,
         "Gardner, Alexander"@pt,
         "Гарднер, Александр"@ru,
         "جاردنر, أليكسندر"@ar,
         "加德纳, 亚历山大"@zh;
... (and so on and so forth)
     dcterms:title "Antietam, Maryland. Allan Pinkerton, President Lincoln, and Major General John A. McClernand: Another View"@en,
         "Antietam, Maryland. Allan Pinkerton, el Presidente Lincoln y el General Principal John A. McClernand: Otra visión"@es,
         "Antietam, Maryland. Allan Pinkerton, le président Lincoln et le général-major John A. McClernand: Autre vue"@fr,
         "Antietam, Maryland. Allan Pinkerton,  Presidente Lincoln e Major-General John A. McClernand: Outra Vista"@pt,
         "Антитэм, штат Мэриленд. Аллан Пинкертон, президент Линкольн и генерал-майор Джон А. Макклернанд: Другой снимок"@ru,
         "أنتينام، ميريلاند ألان بينكرتون، الرئيس لينكولن، واللواء جون أ. ماكليرناند: منظر آخر"@ar,
         "安蒂特姆，马里兰州 艾伦·平克顿、林肯总统和少将约翰·A ·马克克拉南: 另一个视角"@zh;
     ore:aggregates <http://localhost/static/c/1/reference/04326u_thumb_item.gif>,
         <http://localhost/static/c/1/service/04326u.tif>;
     ore:isDescribedBy <http://localhost/en/item/1/item.rdf>;
     rdfs:seeAlso <http://hdl.loc.gov/loc.wdl/dlc.1>. 
 
 <http://localhost/static/c/1/reference/04326u_thumb_item.gif> a _27:FileDataObject;
     dcterms:format "image/gif";
     _27:fileSize "34531"^^<http://www.w3.org/2001/XMLSchema#long>. 
 
 <http://localhost/static/c/1/service/04326u.tif> a _27:FileDataObject;
     dcterms:format "image/tiff";
     _27:fileSize "1301614"^^<http://www.w3.org/2001/XMLSchema#long>. 
 
 ore:Aggregation rdfs1:isDefinedBy <http://www.openarchives.org/ore/terms/>;
     rdfs1:label "Aggregation". 
 
 ore:ResourceMap rdfs1:isDefinedBy <http://www.openarchives.org/ore/terms/>;
     rdfs1:label "ResourceMap".

You might pick up on some warts I have yet to fix, but there you go.

I finally pushed out some embarrassingly outdated WordPress plugin updates a few moments ago.

• Updated unAPI plugin with a patch contributed by Jay Luker that removes the hard-coded "wp_" table prefix. The updated version of the plugin has been tagged as 1.4.1.
• Updated LinkPURL plugin with a patch contributed by Mark Matienzo that enables partial redirects. I made some additional tweaks to the plugin to make this feature configurable via the WordPress management UI. This has been tagged as 1.1.
• Created a new unAPI plugin branch for Mark Matienzo's Scriblio-oriented tweaks. The branch is called 1.4.1-anarchivist-scriblio and it contains the scriblio.diff file. I have yet to integrate the diffs, as the file that was patched has changed since the patch was issued. If anyone is interested in working on unAPI/Scriblio integration, please get in touch with me.

And here is my to-do list which I hope will keep me honest.

• Update OAI-ORE plugin to support version 1.0 of the ORE specification.
• Add per-post (and per-page?) resource maps that wrap all embedded images and links.
• Enable "cool URIs" for all resource maps.

It is my hope that I'll get to those sometime before the summer begins. :)

I've been using my time at RepoCamp today to get the OAI-ORE plugin for WordPress validating again.  I'm having some trouble using the validator so I say that with some diffidence.  But the latest code which is now checked in to the WordPress plugins svn repo ought to be close, if not fully conformant, to the 0.9 version of the ORE spec.

I'm not sure the plugin is really useful; it's just an Atom feed of all posts and pages in a WP instance.  I can think of some ways to make this more useful, by allowing blog authors to create their own aggregations, pulling in content outside of the particular instance.  I am certain that others can come up with even better uses.  I'm open to suggestions.

Thanks to Jay Datema for prodding me a bit, if indirectly.

This is very rough, but here's a WordPress plugin that provides a resource map for the aggregation of all posts within an installation of WordPress. I'll be working on this some more, but for now, it does appear to work and validate (as Atom). Useful? If so, I'll zip it up and commit it to the wp-plugins svn.

Note:Ed reminds me that xsltproc can be used to transform the Atom-based resource map into RDF via GRDDL:

xsltproc http://www.openarchives.org/ore/atom-grddl.xsl http://lackoftalent.org/michael/blog/wp-content/plugins/oai-ore/rem.php

Update: The plugin has its own page.