In recent years, the ISO-SGML (Standardized Generalized Markup
Language) tagging convention has begun to be used extensively, most
notably with HTML and the World Wide Web . An
SGML tag surrounds a body of information with an opening and
closing label. The opening label is of the form <lbl>
and the closing label is of the form </lbl> where the type
label lbl can be almost any sequence of symbols. SGML is
extremely flexible since it allows for an infinite number of different
labels, it allows for an arbitrary depth of nested tags, it is
relatively economical in terms of storage,
and, because of the angle brackets
>, it easy to recognize
the beginning and end of a body of information.
For these reasons, the ISO-SGML tagging convention was chosen for
use in the Darwin genetic database structure.
The SearchTag function searches an item of type string for an
opening and closing SGML tag and returns the information contained
between them. The general syntax is
where taglabel is an SGML type label and target is an arbitrary name.
> SearchTag('AC', > '<ID>11S3_HELAN</ID><AC>P19084;</AC><DE>GLOBULIN</DE>'); P19084;
We examine a number of related routines in Chapter - Genetic Databases.