Although the within-component structure of a component is considered a black box, the Dexter model is concerned with the possible values that can be used to specify a part of a component that can be an anchor, an endpoint for links. In Intermedia for instance, the components are complete structured documents. Links are possible not only between documents, but between "spans" of characters within one document and spans of characters within another document. Anchors (see anchoring in the Dexter model) are a mechanism that provides this functionality while maintaining a clean separation between the storage and within-component layers. The within-component layer must deliver the data type that is to be used to identify parts of a component in a way the within-component layer understands (and also in another way the storage layer understands).