Usage of databases are really straightforward nowadays: create the schema then fill the tables with your data. Tables and models behind the schema are hard to change, because it is unexpected to change them too often. You made a decision, live with it. Also, the schema and the data is seperated that you can not modify them at the same time and the same way.
RDF (Resource Definition Framework) is a common way to describe things in the Semantic Web. It is XML based which has the befenit of understanding both humans and machines. XML also supported by hundreds of applications, organizations, browser and protocols. RDFS which is RDF’s schema language brings new features to the Semantic Web by allowing definition of classes, types, restrictions etc. OWL extends the whole framework with the ability of adding more details. Not only can you enhance your schema with detailed definitions, rules but also allows you the ability of inference.
SPARQL should come to your mind if you want to work with Semantic Web or you simply have an RDF based database. SPARQL as a query language is a great way to certain data from your database. It is SQL-like so it is easy to learn, easy to use and also recommended by W3C. As a standard, lots of database managers or service providers support it unlike its update language or SPARQL 1.1 that contains both querying and updating features.
Why are they so important? The answer is that they are all keys to manipulate the schema and the data of your database the same way, at the same time. The last thing we need to consider is a dynamic presentation of the data, eg. using Silverlight. With all the ability that a Silverlight application holds, one can be sure that managing data will be better, it will be easier to follow the changing needs. You will be able to create an own database with an own view of it and also will be able to share it with others. A display/editor should be type based so that every class has its own viewer or should be displayed as a part of a common control. For the user it means a formatted version of the graph that holds the data. This application frame gives you the ability to present and manage all your data using Silverlight and all the predefined primitives.