Gloss of "Text"

Texts used as FDL content are simple recursive structures, ie, they are abstract structures rather than character strings. We take issues of parsing strings into structures and displaying structures to users to be matters ordinarily extraneous to criteria pertaining to formal properties of expressions such as criteria for correctness. See Formal vs Informal and Words vs Formality.

For purposes of accounting the nature of texts is important only insofar as there is a determinate notion of occurrences within texts of Abstract Identifiers. For purposes of typical syntactic analysis used in formal languages, however, the subexpression relation is dominant and so we have adopted a syntactic form for texts in which that relation is dominant and explicit.

The text structure is iterated operators on subtexts. In addition to its subtexts, a text contains a sequence of labelled values presupposed by the construction of texts, which we call Pro-textual Constituents; character strings and Abstract Identifiers are among these pro-textual values. An individual text consists of a sequence of zero or more pro-textual constituents together with a sequence of zero or more immediate subtexts; further, any such pair of sequences constitutes a text. The sequence of pro-textual constituents may be construed as identifying the "operator" of which the text is an instance, or sometimes this sequence together with the number of subtexts is construed as the operator.

Binding structure, however, ie, which expressions are variables and which become bound in which texts, is not considered part of the text structure as far as the FDL is concerned. Binding structure is attributed to texts by the Clients. The reason for this is that there are significantly divergent approaches to binding structure, and to build one in would be an unacceptable bias. We believe that issues of binding structure remain open among different groups of prospective FDL clients, that they will be the subject of further innovations, and that disputes should be waged among clients and not between FDL designers and clients. IF YOU CAN SEE THIS go to http://www.cs.cornell.edu/Info/People/sfa/Nuprl/Shared/Xindentation_hack_doc.html