1. A computer-implemented method comprising, storing, within a repository, a plurality of compound documents, each compound document of the plurality of compound documents including: a parent document, a plurality of subdocuments of said parent document; wherein the parent document includes, for each subdocument of the plurality of subdocuments, a link to said each subdocument; storing, in association with a first compound document of the plurality of compound documents, a first compound document declaration that declares a first type of link; storing, in association with a second compound document of the plurality of compound documents, a second compound document declaration that declares a second type of link that is different than the first type of link; wherein the first type of link is one of a hard link, a weak link, or a symbolic link; wherein the second type of link is another one of the hard link, the weak link, or the symbolic link; wherein the hard link is a link such that a first subdocument that is a target of the hard link cannot be deleted from the repository as long as the hard link is included in a first parent document, wherein the hard link is uniquely associated with the first subdocument, and wherein the hard link between a first parent document and the first subdocument is preserved if the first subdocument is moved to another location within the repository; wherein the weak link is a link such that a second subdocument that is a target of the weak link is uniquely associated with the weak link and can be deleted from the repository even while a second parent document includes the weak link to the second subdocument; wherein the symbolic link is a link such that a third parent document that includes the symbolic link is no longer linked to a third subdocument that is a target of the symbolic link if the third subdocument is moved to a different location in the repository, wherein the symbolic link is not uniquely associated with the third subdocument; wherein the method is performed by one or more computing devices.