RDF--Connecting Knowledge Nuggets in the Online World

RDF is a fascinating standard for the person who wants to connect pieces of knowledge in the online and/or digital world. Knowledge management has always been a favorite topic of mine. Maybe because of my background in higher education where I found it very rewarding to help learners learn and aid in the process to provide staff and faculty with all the data/information they needed in order to make "evidence based" decisions.

The quoted highlights below come from a 3 page paper on the topic of "What is RDF?". Please click the title of each section to find the original article on XML.com. And if you would like to see the entire article with my highlights included--feel free to click the "annotated" link just to the right of the title.

XML.com: What Is RDF  Annotated

tags: metadata, rdf, semanticweb, xml

The current web is a decentralized platform for distributed presentations, while the SemWeb is a decentralized platform for distributed knowledge.

Resource Description Framework (RDF) is the W3C standard for encoding knowledge.

The real content, the knowledge the files are conveying to the human, is opaque to the computer.

What is meant by "semantic" in Semantic Web is not that computers are going to understand the meaning of anything, but that the logical pieces of meaning can be mechanically manipulated by a machine to useful human ends.

Life can't be neatly packed into tables, as in relational databases or hierarchies, as in XML.

Files on the Semantic Web need to be able to express information flexibly.

Start Node Edge Label End Node vincent_donofrio starred_in law_&_order_ci law_&_order_ci is_a tv_show the_thirteenth_floor similar_plot_as the_matrix

Files on the Semantic Web need to be able to relate to each other.

We will use vocabularies for making assertions about things, but these vocabularies must be able to be mixed together.

RDF was originally created in 1999 as a standard on top of XML for encoding metadata

Since then, and perhaps especially after the updated RDF spec in 2004, the scope of RDF has really evolved into something greater. The most exciting uses of RDF aren't in encoding information about web resources, but information about and relations between things in the real world: people, places, concepts, etc.

XML.com: What Is RDF--Page 2  Annotated

tags: metadata, rdf, semanticweb, xml

Most of the abstract model of RDF comes down to four simple rules:

A fact is expressed as a Subject-Predicate-Object triple, also known as a statement. It's like a little English sentence.

Subjects, predicates, and objects are given as names for entities, also called resources (dating back to RDF's application to metadata for web resources) or nodes (from graph terminology). Entities represent something, a person, website, or something more abstract like states and relations.

Names are URIs, which are global in scope, always referring to the same entity in any RDF document in which they appear.

Objects can also be given as text values, called literal values, which may or may not be typed using XML Schema datatypes.

Entities are named by Uniform Resource Identifiers (URIs), and this provides the globally unique, distributed naming system we need for distributed knowledge.

There are also other types of URIs besides http: URIs, such as URNs and TAGs, which you'll see below.

Since URIs can be quite long, in RDF notations they're usually abbreviated using the concept of namespaces from XML.

In an RDF/XML document there are two types of nodes: resource nodes and property nodes.

Notation 3 (N3), or Turtle, is another system for writing out RDF.

XML.com: What Is RDF--Page 3  Annotated

tags: metadata, rdf, semanticweb, xml

The simplicity and flexibility of the triple in combination with the use of URIs for globally unique names makes RDF unique, and very powerful.

It's a specification that fills a very particular niche for decentralized, distributed knowledge and provides a framework to enable computer applications to answer questions we wouldn't dream of asking computers today.

tag: digital world, RDF, XML, Semantic Web, metadata, Knowledge Management

Diigo V3 released

More Reading on Identity Management

The following is actually two articles, but both provide excellent points on the good and bad of both OpenId and LiveId (Microsoft) technologies.

IdentityBlog - Digital Identity, Privacy, and the Internet's Missing Identity Layer Annotated

tags: identity

Classic PKI (digital certificates) are a good example of third-party identities that you can inspect and choose to trust or not. But client-side digital certificates have deployment shortcomings. Very few people use them.

A promising alternative to client-side certificates is the new breed of digital identity architectures, many of which do not require a huge, monolithic corporate infrastructure to issue. I’m thinking mostly of OpenID and Microsoft’s CardSpace specs.

When you want to express a claim about your identity, you pick a card (any card!) and present it to the person who’s asking.

What’s nice about InfoCards is that, in theory, these are things you can create for yourself at a registrar (identity provider) of your choice. InfoCards also have good privacy controls — if you don’t want a relying party (e.g., securitymetrics.org) to see your e-mail identity attribute, you don’t have to release that information.

So, InfoCards have promise. But they use the WS-* XML standards for communication (think: big, hairy, complicated), and they require a client-side supplicant that allows users to navigate their InfoCards and present them when asked.

OpenID holds more promise for me. There are loads more implementations available (and several choices for Java libraries), and the mechanism that identity providers use to communicate with relying parties is simple and comprehensible by humans. It doesn’t require special software because it relies on HTTP redirects to work. And best of all, the thing the identity is based on is something “my kind of people” all have: a website URL. Identity, essentially, boils down to an assertion of ownership over a URL. I like this because it’s something I can verify easily. And by visiting your website, I can usually tell whether the person who owns that URL is my kind of people.