This informal protocol declares the two methods writeSelectionToPasteboard:types: and readSelectionFromPasteboard:, which classes may implement to interact with system services found in the Services menu. The first of these, writeSelectionToPasteboard:types:, is used to provide data to a service, while readSelectionFromPasteboard: is used to retrieve data from a service.

@interface NSObject (NSServicesRequests)
// Instance Methods
- (BOOL)writeSelectionToPasteboard:(NSPasteboard *)pboard types:(NSArray *)types;
- (BOOL)readSelectionFromPasteboard:(NSPasteboard *)pboard;
@end