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Notes on “Ontologies Come of Age”

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Ontologies Come of Age, Deborah L. McGuinness (2002)

One thing I noticed about this reading is the ample use of examples. If you look through all of the points below “Structured Ontologies and Their Uses” you can see what I mean. I find that to be a big problem with a lot of the things I’ve read about ontologies or the semantic web—there’s a lot of terminology and very little illustration. So in that regard, this was a good reading.

On the other hand, the more I play with Protege and read about ontologies, the more it seems to me that all the information science and library science people are moving closer and closer to the way relational databases work, without actually knowing it. For example, each of the classes in an ontology could be thought of as tables. The class/subclass relationship is like a one-to-many foreign key relationship, and since you can have more than one parent for any particular class you can have many-to-one and many-to-many relationships as well. Each of the fields or “slots” is just like a field in a relational table. There are only a few ways in which ontologies and relational databases differ, and they’re only really cosmetic differences. Relational databases have no notion of inheritance, for example, so fields for a table called “Thing” are not passed down to other other tables that have “thing_id” as a foreign key. But database applications and users create views which join the tables and do something similar. Also, Protege allows you to use a class or and instance as the type for a slot, whereas in relational databases it really only makes sense to use an instance.

There must be other people who have noticed this, and since a lot of web pages have relational database back-ends I have to assume semantic web pages will as well.

Notes on “Metadata Principles and Practicalities”

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Metadata Principles and Practicalities, Duval, Erik, Wayne Hodgins, Stuart Sutton, Stuart L. Weibel (2002).

This was a pretty straight-forward reading. I did like the Lego metaphor for metadata, but it would be nice if it was elaborated on a little bit more. So, kids have no problem combining space ship Lego parts with medieval castle parts, but just because it is possible to do so, is it beneficial or useful in any way? I understand they are just talking about modularity as a quality at the point, but it also gives the impression that metadata schema, properly constructed, can be mixed and matched willy-nilly.

One thing I have not seen discussed very much is where the line is drawn between metadata and regular data. For example, most schema have some sort of author/creator field. I see how the author could be data describing and article, but if you look at articles in a journal or on a web page, the author is almost always presented along with the body text. A more clear example of what I’m trying to say is an article’s abstract. I’ve see some schema that have the abstract as a piece of metadata, but does that mean it is not part of the data (the article) itself? Or is it both?

It all depends on your point of view. From a database designer’s perspective, all of theses metadata fields are just data, and metadata is what describes the structure of the database—field types, lengths, foreign key relationships, etc. I’m not saying that everything should be stored in one big lump. I guess I’m just concerned that depending on the point of view, metadata could mean anything. Really, all of this is just a matter of properly separating different data elements from each other. Obviously author/creator should be a separate field from article body text. And date, titles, etc. should be separate as well. But that doesn’t really separate them from the thing itself, they are still all aspects of the thing.

Notes on the UMLS Semantic Network

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UMLS Semantic Network

This was a really interesting reading. Not interesting like a novel or movie, of course, but interesting because I keep hearing about semantic webs without seeing any worthwhile examples.

One thing I was a little surprised to see was the ASCII codes for creating a flat-file database. I would have through they would have either specified it in XML or something a little more modern. And I kind of cringe whenever I hear anyone call an ASCII file a database. Even though it’s technically true, to me ‘database’ means database management system (DBMS), with some mechanisms put into place to allow multiple users, referential integrity, etc. If everything is stored in ASCII files, than any idiot can ruin the whole system and it’s really, really easy to let data get corrupted. You have to do all sorts of extra work to make sure updates to one field cascade through the rest of the file.

Even through this was designed specifically for the medical field, it’s surprising how much their relationships and semantic types could be useful for almost any semantic web. I could only think of a few relationships that were missing, the chief one being requires. This is a relationship that’s very common in computer science, but I think it might apply fairly often in other fields as well. When and entity requires another it cannot exist without it. It’s kind of a mix between part_of and precedes.