Laszlo Turi <[log in to unmask]> asks:
>I have received a leaflet from Oxford University Press offering
>a program called SGML Tagger. As the leaflet says this is
>"a program which adds SGML to computer based documents".
>Is there anyone out there who has already tested this package and
>would share her/his experience? My primary question is this:
>According to the leaflet "SGML Tagger works out what markup is
>allowed, and will only let the user insert a tag which is correct
>in that particular context." However the leaflet also says that
>"it reads the part of the document that is on the screen, then offers
>a choice of SGML markup for insertion." How can the program find
>out the relevant context if an element is longer than the current
>screen, i.e. longer than 25 lines? In other words: how does the
>tagger know the structure of the complete document if it sees
>only a screenful of it?
Although I am unfamiliar with this particular product, it sounds to me that
this is an SGML editor. SGML editors keep track of where you are in a document
by means of the DTD (Document Type Definition) which describes the structure of
a document using elements with optional and/or required attributes and/or
entity references plus a minimal number of other items. Since the DTD
describes which elements are allowed as children of any particular element, it
is possible for the editor to present a limited number of choices of what is
allowed as the next element quite simply. After that, all that is required is
for the editor to maintain a linked list, stack, queue or tree representing the
parent-child relationship history and back out of it when any element is ended.
It has nothing to do with how much text is or is not displayed on the screen
at any moment.
One caution might be in order. Since every SGML document requires a DTD at
it's heart, it ought not to be surprising that some people claim that the
creation of the DTD is the hardest part of doing SGML. If you do not have a
DTD already created to describe your particular document(s), you must
anticipate a great deal of work will be required of you (or an SGML consultant)
before you can use SGML Tagger or any other SGML editor. The program probably
comes ready to run off the shelf with a provision that you must supply it the
appropriate valid DTD for it to use before you will be able to create an SGML
document instance with the editor.
If these concepts are unfamiliar to you, I would recommend you obtain the TEI
P2, Chapter SG fascicle which is entitled "A Gentle Introduction to SGML". I
would also be happy to answer any questions which arise from your reading of
that document or refer you to someone who would be able to answer your question
should my own grasp of the subject be insufficient to the task.
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