The Rebound

Photo by Jamesfishcer. Obtained via Flickr Creative Commons, 8/8/08

I was off the grid for the last few days, due to a migraine that left me bedbound and screaming alternately for morphine and a lobotomy. It didn’t help that the Blue Angels were doing their annual Sea Fair fly-by all weekend, breaking the sound barrier over my head like so many anvils.  But I’m happy to say that I’m back, both mentally and physically, and feeling the need to catch up on all things library! 

In the fall, I will be taking a class on metadata, for which I am very excited.  In library science, metadata can refer to so many things, from the theoretical concepts of the semantic web to specific metadata schemas, intended to add value to datasets (and to the web at large) and to allow for controlled search and description.  I’m hoping this class gives me some practical experience with creating metadata and inspires ideas for implementing it at my work library.  

My professor e-mailed the class over the weekend to tell us of a book called Semantic Web for the Working Ontologist: Effective Modeling in RDFS and OWL by Dean Allemang and James Hendler that will apparently give us a leg up on the the practical and conceptual stuff before class begins.  Though the book is retailing for way more than I want to spend, I’m thinking about buying it anyway.  The only area library that seems to have it is UW, and somebody’s got it checked out until October.  What can I say, my curiosity is piqued.

Photo by Parksy1964. Obtained via Flickr Creative Commons on 8/08/08

I’ve never worked with the ontologies mentioned in the book’s title, but I took a look at the OWL Ontology Language Guide to see what it was all about.  As an ontology, OWL attempts to capture and describe the various ways that words are related to each other, thus allowing searchers to form queries that stretch beyond the bounds of simple Boolean logic.  Here is an excerpt from the guide that describes the specifics:

OWL is a component of the Semantic Web activity. This effort aims to make Web resources more readily accessible to automated processes by adding information about the resources that describe or provide Web content. As the Semantic Web is inherently distributed, OWL must allow for information to be gathered from distributed sources. This is partly done by allowing ontologies to be related, including explicitly importing information from other ontologies.

In addition, OWL makes an open world assumption. That is, descriptions of resources are not confined to a single file or scope. While class C1may be defined originally in ontology O1, it can be extended in other ontologies. The consequences of these additional propositions about C1 are monotonic. New information cannot retract previous information. New information can be contradictory, but facts and entailments can only be added, never deleted.

The possibility of such contradictions is something the designer of an ontology needs to take into consideration. It is expected that tool support will help detect such cases.

Do I fully understand this? No.  I’m going to spend some quality time with OWL today, though, and see about checking out some materials about the semantic web from work.  Maybe I’ll post more about OWL once I get a handle on it.