One problem with the move to XML and RDF syntaxes, away from simpler syntaxes like those used in SHOE, is that it is hard, as a human, to read the semantic markup, and even harder to debug the markup one has written oneself -- remembering when prefixes can be used, when to put things in quotes, etc. can be very difficult.
To address this, a new notation has been evolving that allows humans to better handle the information but is still formal enough for machines to use. At the time we write this, these languages are still evolving, but we give one example to show the idea. This is based on N3/DAML -- that is, a DAML file expressed in the Notation of Triples (N3) language.
Here are the same things as we showed in Step3 for the markup of the home page we've bee discussing.
# Base was: http://www.cs.umd.edu/users/jhendler.daml
@prefix : <#> .
@prefix StanfordKSL: .
Prefixes are now defined explicitely ("<#>" is a shorthand for "this same document.")
:JimHendler a ShoeGen:Person,
StanfordKSL:Person;
CmuAtlas:sex ShoePers:Male;
ShoeGen:head :PlusLab;
ShoePers:age "about 44 ";
ShoePers:child " http://www.cs.umd.edu/users/hendler/sharon.html";
ShoePers:emailAddress "jhendler@darpa.mil";
dex:hasHeight dex:short;
StanfordKSL:has-Full-Name "Professor James A. Hendler, PhD" .
In this case we used one statement that expressed that the new instance is an instance of both the ShoeGen and StanfordKSL person definitions, with the properties as listed. Begin and end tags are implicit, and the notation reads like a set of slot/filler pairs.
CmuAtlas:Project daml:equivalentTo ShoeGen:Organization .
and notice that the "equivalentTO" statement now can use prefixes.
A similar benefit can be seen in the ontology files. For example,
ex:father a :Property;
:subProperty ex:parent;
:range ex:Man;
:cardinality "1" .
is now how we say that a father is a kind of parent, must be a man, and you can only have one of them.
As you can see from the time and effort it has taken you to reach this point, the Semantic Web is growing in both power and complexity. From the early days of SHOE, to the future world of web ontologies, ruies, logics and proofs, we see a constant and growing excitement. We welcome you to the rich world of web semantics, and hope you'll read more of the articles and papers linked to the article we've written.
----- Jim Hendler, Ora Lassila, and Tim Berners-Lee.
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