http:www.albany.eduhammondgellmu The GELLMU Archive The didactic GELLMU production system provides a command anch for anchors that is parallel to the HTML anchor tag a An example of basic usage is given by the following markup for an anchor to the World Wide Web Consortium (W3C): anchhrefhttpwwww3orgthisanchor The markup is used here for href="http:www.w3.org"this anchor The urlanch command provides a succinct way to insert an anchor whose visible content is the referenced URI. The name urianch would be more correct since its content is a URI. Either of these commands may be used in a display, as here: http:www.w3.org. One may ask whether there is a difference between the use of a macro Urlanch defined by newcommandUrlanch1anchhref1path1 and urlanch The latter is used here: href="http:www.w3.org"http:www.w3.org. There is a difference The command urlanch corresponds to an SGML element, while anything defined with newcommand is fully expanded by the GELLMU syntactic translator before SGML generation This means that the treatment of urlanch by a formatter is completely independent of the treatment of anch and path by a formatter, while the treatment of Urlanch, if so defined, is entirely dependent on the formatters treatment of the other two names Whether it is sensible to undertake the effort of coding formatters to handle the SGML element urlanch in addition to the SGML elements anch and path depends upon whether or not one imagines that there is at least one hypothetical output format for ones document type that might benefit from independent treatment. With the default GELLMU formatter for , for example, a footnote is created with Urlanch but not with urlanch (A footnote might also be avoided by using a different attribute name Href instead of href, but that still does not make the issue vanish.) If one thinks about these issues solely in terms of formatting from GELLMU markup to , one will come to realize that there are several approaches to the needs traditionally met in the world with packages: macros()Using macros such as newcommand for SGML generation formatters()Carefully crafting formatters from ones document type to packages()Writing packages to receive various SGML (or XML, of course) document types. In fact, it is generally easier to write formatters for document types that are formally XML On the other hand, writing SGML is easier for authors Since an SGML parser can, for most document types, convert SGML to XML, it is sensible for document types used with GELLMU to have both SGML and XML definitions.