The NSDL is comprised entirely of metadata. In fact, the library doesn't house any educational resources at all. Instead, we keep track of information about the resources (like their URL locations, the name of their creator, and their educational level). This information allows us to create advanced searching options for users at nsdl.org.
Metadata is data about data. Take, for example, your music collection: you might have hundreds or even thousands of songs on your computer. These songs are probably saved in mp3, wav, mp4, or another audio file format. The file itself is your music data. Hopefully, you also have information about this data, such as song title, musician, album title, recording date, and perhaps music genre. This is your music's metadata. Metadata is extremely important for locating, using, and preserving the vast amounts of data we store on computers. Imagine trying to access your music collection without knowing the song titles or musician names!
At the NSDL, we collect metadata about educational resources to help users (like teachers and students) better find and access them through our search interface. This metadata is stored as an xml record. Xml is a file format for storing and transferring data as text (a good place to learn more about xm; is w3schools.com). Collection builders create these xml records and send them to the NSDL, where we store them in a central repository that can be indexed for the website's search interface to search across.
Click on the child pages below to find more information about the xml formats we use for metadata, and the methods of metadata transfer between the library and collection builders.