Property paths

Property paths will make queries both more powerful and easier to write. Some cases resemble XPath/XQuery:

Find the names of people 2 “foaf:knows” links away.

{
 ?x foaf:mbox <mailto:alice@example> .
 ?x foaf:knows/foaf:knows/foaf:name ?name .
}

… whereas others generalize the idea of transitive closures, which is also relevant in our applications that work on RDF extracted from OMDoc or OpenMath (e.g. finding imported theories, computing dependencies, and checking MMT well-formedness):

Find the names of all the people that can be reached from Alice by foaf:knows:

{
 ?x foaf:mbox <mailto:alice@example> .
 ?x foaf:knows+/foaf:name ?name .
}

Update language

Other features to come are an update language, probably inspired by XQuery Update.  That would, assuming a triple store that supports it, e.g. make it easier to integrate Krextor into applications.

Entailment regimes

Besides enhancements to simple queries, the behavior of SPARQL under different entailment regimes (e.g. RDFS or OWL – in practical terms: what happens when you attach a reasoner to your triple store) will be clarified.

Miscellaneous

In the core of the language, certain other goodies will be specified, such as an easier syntax for negation-as-failure and subqueries (nested queries).

• ¬∃knows.TroubleI’veSeen (Spiritual)
• Bier ⊑ ¬∃gibtsAuf.Hawaii ⇒ Ich ⊑ (¬∃fahreNach.Hawaii)⊓(∀bleibe.Hier) (Kuhn, 1963)
• ¬(⋄I ⊑ ∃get.¬“⊨”) (Jagger/Richards, 1965)
• ¬∃ b:Business . b = ShowBusiness (Berlin, 1946)
• I ⊑ ∃shot.Sheriff ⊓ ∀shot.¬Deputy (Marley, 1973)
• ¬(⊥ ⊓ ¬HoundDog) (Presley, 1956)
• ¬∃ ¬Sunshine ← gone(She) (Withers, 1971)
• ∀x ∃y . needs(x, y) ∧ loves(x, y) (Blues Brothers, 1981)
• I ⊑ ∃feel.(Pretty ⊓ Witty ⊓ Gay) (Bernstein/Sondheim, 1961)

(defun bibtex-insert-current-urldate ()
  (interactive)
  (bibtex-make-field
  '("urldate" "" (lambda () (format-time-string "%Y-%m-%d" (current-time))))
  t))

The following line binds it to the keyboard shortcut C-c u:

(add-hook 'bibtex-mode-hook '(lambda ()
			       (define-key
				 bibtex-mode-map [(control c) ?u]
				 'bibtex-insert-current-urldate)))

With the default BibLaTeX style, the urldate field will render as (visited on MM/DD/YYYY).

1. are slightly easier to use for people who don’t understand XML namespaces
   • granted, RDFa’s excessive reliance on XML namespaces makes it hard to parse, and makes it unbearably complex to copy/paste a fragment, which is an important use case for HTML5
2. allow for ad hoc pseudo-semantic markup when you do not use an ontology
   • What’s the point in annotating at all, then?
3. compatible with the non-XML syntax of HTML5 (which should have been ditched IMHO, but, well, in the interest of reactionary users and software, they decided differently)

The fight for the future of RDFa in HTML is going on, but what does that mean to KWARC? We have incorporated RDFa into OMDoc as a means of extending the metadata vocabularies. RDFa, originally designed for XHTML, is prepared for being integrated into any XML language, including OMDoc. HTML5 microdata are an integral part of the HTML5 specification and would not work in other XML languages. OK, but we present OMDoc documents as HTML to make them human-readable. In this output, we want to preserve the semantics of the OMDoc markup, and for that we had always been thinking about using RDFa. (We know exactly how to do it, but just have not yet implemented that step, though.) We could use HTML5 microdata instead, but:

1. RDFa has little software support so far, but microdata have none (beyond proofs of concept)
2. We generate XML-compliant HTML. The non-XML syntax of HTML5 supports embedded MathML, but I doubt that it will support parallel OpenMath markup, where elements from yet another namespace are embedded into the MathML formulae.
3. We generate HTML. The embedded annotations need not be authored manually, so they do not have to be easy to author.
4. We are interested in using well-defined ontologies to express semantics, so we don’t need ad hoc “semantic” markup.

What do you think?

pdfnup doc.pdf --nup 2x1 --trim "-6cm -6cm -6cm -6cm" --delta "-18cm -18cm" --scale 1.8

Update: Formatting your PDF right

It is even better if you already set the right paper format when creating your PDF. With appropriate printing settings, that gets the print right without the adjustments mentioned above, and it makes screen reading more convenient. Markus Kuhn explains how. However, his measurements didn’t work for me; instead of 92 112 523 778 I had to use 91 71 521 721.

The document “Krextor – An extensible XML→RDF extraction framework.pdf” is no longer available on docstoc.
It has either been removed by the original owner of the document or by the docstoc staff due to copyrighted or inappropriate content.

Isn’t that actually a proof of success, in this new age of the Pirate Party?

Here is where it was stolen from, and here is the paper.

\usepackage{savesym}
\savesymbol{todo} % occurs in both packages
\usepackage[show]{ed}
\restoresymbol{ed}{todo} % now available as \edtodo
\usepackage{todonotes}

• KiWi’s strength as a scalable and extensible platform for social software (not just as a semantic wiki!) is its architecture. Based on EJB3 and Seam, it has an incredibly steep learning curve – EJB was one of the topics that I tried best to avoid when studying, now I regret that; on the other hand it also took the people at Salzburg Research several months to come up with that elaborate architecture.
• Openness attracts the community: The KiWis decided to open their programming camp to external developers, as a first effort to start community-building.  They were really committed also to teaching me, the visitor, how to use their system (thanks, Mihai, Rolf, Sebastian, Stephanie, Szaby, Thomas – and their colleagues from Aalborg, Brno and Munich as well!). Even before the programming camp, they did not jealously lock away their sources, but gave external interested people access.  And now, with further adoption of the software in mind, they are switching to the most liberal license, i.e. BSD.
• With our Subversion and Trac infrastructure, we have done great steps towards more productive development. Still, the KiWis leverage more professional tools, which really make life easier. OK, they are not open source, but require considerably less hacking in order to make them productive: Jira (bug tracker), Fisheye (repository browser), Crucible (code review system, not yet used), and Hudson (automated integration tester).

“KiWi knows” what else I will be able to report in the near future – stay tuned!