I can spell RDF, RDFS, and OWL; but that's about all I can do, so bare with me.
I think I need an RDF editor.
In Eclipse, I've been playing with TopBraid Composer, which I understand is for working with ontologies. And 'ontologies' I understand to mean class structures written in RDFS or OWL. Um, OK?
So now I have what I think may be a valid ontology, I'd like to create some instances of my shiny new classes. I need RDF for that, right?
I can't be alone in this. When you are working with RDF, do you work in a text editor, or is there a more specific tool out there?
For small chunks of RDF (or RDFS/OWL) I usually just use a text editor. For producing RDF in larger quantities I'm usually creating it programmatically based on data in a database or a file.
You can create instances in TopBraid Composer too.
Just right click on an ontology class and select Create New Instance...
Then you will be asked to identifier of the new instance.
Next you get a view where you can populate some properties.
But beware - TopBraid shows all properties that have the same rdfs:Domain which can lead you to some wrong conclusions if you come from OO background. Like that rdfs:Domain links a property to a Class like in OO design. Keep in mind that you have to fill only the properties that you want, not everything and that you can add more properties from the plus button in the top right corner.
Also there is an Instances panel in the bottom of the central panel. It shows all instances that are from the currently selected type.
I got fed up manipulating RDF in basic text editors so I produced my own - rdfEditor - which is part of the dotNetRDF Toolkit.
It has syntax highlighting, auto-completion for some formats (Turtle/N3 and SPARQL) and validate as you type.
There is a terrible quality screencast on YouTube (sorry but I have a rubbish mike and screen recorder software) which demonstrates an earlier version of the editor. There will be a new release soon which adds various features that just didn't make it into earlier versions (including Find & Replace, double click to symbol select, disable BOM for UTF-8 output)
You may want to have a look at Protégé, which is an ontology editor, but can also be used to enter individuals/instances. It may be a bit over the top, though, as it's a quite large and complex tool.
It is not free (well, fairly pricy, in fact) but I had some good experiences with Altova's Suite, if you are o.k. using RDF/XML (and not Turtle). There is also a visual editor for (simple) vocabulary editing, too. It is, in fact, an xml editor (which helps a lot already in filtering out some of the common problems) but knows about the basics of RDF/XML.
I must admit that an average XML editor (in emacs, jEdit, or elsewhere) does help a lot by itself.