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Re: What is a good way to style and show tabular data

Subject: Re: What is a good way to style and show tabular data [snip]
From: Peter Flynn <peter@xxxxxxxxxxx>
Date: 17 Aug 2003 22:22:50 +0100
storing data in xml format
On Fri, 2003-08-15 at 23:41, SANWAL, ABHISHEK (HP-Houston) wrote:
> What is a good way to style and show tabular data 

In a table, usually. 

> and what is a good way to store Tabular data in XML 

There is only one "good" way to store data in XML -- any data -- and
that is in a well-designed structure which preserves as much information
about the data as is needed for you to work with it successfully. Storing
data (or text) in a suboptimal structure, with misleading names, poor
content models, ambiguous attributes, failing to take advantage of some of
the obvious features of XML, perpetrating Tag Abuse, creating Pernicious
Mixed Content, and all the other nasties in the corner; and in a manner 
which loses some metadata as the data is stored, is a recipe for tears and 
grief, as we see daily here and elsewhere :-)

Get the data model right first, and the rest will follow.
Get the data model wrong, and you will spend excessive time
having to undo it or cope with it while it remains wrong.

But in a production situation this is not always possible: data from
elsewhere in a silly format, management insisting white is black when you
know it's actually green, client or vendor insistence on unsuitable, often 
proprietary, formats for political reasons, etc.

For tabular data, there are many solutions, and without seeing an example
any advice has to be general. My personal preference is to use meaningful
names (ie not TR, TD, and TH :-) and to ensure that sufficient metadata
is stored to enable the original structure to be recreated (the "round trip"
test). But in the pressure to get stuff done, you may choose to do otherwise.

But there is one classical case where data is often stored as a table 
quite wrongly: the labelled list. Consider:

	USA	You pay insurance for healthcare, only people
		below a (very low) income level get state-funded care

	UK	You get healthcare free at the point of usage in
		most cases, paid for via income deductions, but
		insurance-funded ("private") healthcare is available

(Forgive me USA and UK if I have the facts wrong :-). To most 
wordprocessor users this looks like a table, because it's the only
way their wordprocessor has of formatting it. But it's not a table:
it's a list whose format resembles a columnar layout. Storing it as
a list in XML lets you choose how to format it for output very easily.
Storing it as a table risks making it uneditable and unformattable
except with much greater difficulty.

> especially when the only purpose for that data is to be styled by 
> stylesheets into XSL-FO (PDF) and HTML - such that the stylesheets 
> are efficient, extensible and not too cumbersome.

There are three common table models: CALS, SASOUT, and HTML (see
Chapter 2, section 3.7 of my book on SGML and XML Tools for a 
detailed description). Another one, ISO/IEC TR 9573 I have lost
track of -- maybe it still exists. CALS is huge, but lets you store
all kinds of fine detail about layout and appearance; SASOUT tries
to let you define the relationships between rows, columns, and cells,
but I don't think it ever really caught on; HTML is simplistic to the 
point of crudity, but better supported in browsers than anything else
(but harder to use for good quality print).

The better the quality of XML markup, the easier it is to work with.
If your markup allows you to record what the data is, and why it is
stored in this way, it's usually much easier to write a stylesheet
to format it than having to spend large amounts of time coding large
nests of conditionals to try and deduce aspects of the nature of the
data which ought to have been stored explicitly. But as I said, this
is the ideal: in practice most people stuff it into TR, TD, and TH
and hope for the best.


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