Limitations of SGML

1. SGML allows cross-referencing within the same document. This can be done by assigning unique identifiers to elements that need to be referred to elsewhere. However, the uniqueness of the identifier (and hence, the element) is applicable only within the current local document. Hence, only elements within the same document (and only those having unique identifiers) can be linked. Therefore, this mechanism can only be used in a hypertext document to refer to elements within the same document and not other documents.
2. SGML cannot support time dependent data such as audio and video and also graphics and images. Rendering of events is not possible in SGML, that is, displaying a map of NY and a link that zooms into Manhattan.