CS73N Meeting 12 Notes: Standards, 20 Feb 2003

Started by Gio Wiederhold, 27 February 2001, updated Feb 21, 25 2002, 20 Feb 2003.

XML DTDs: Define B2B interaction.

Origin of XML is in document processing, hierarchically structured + links, more; ordered (except for attributes).

Main data type is Character data

• tags with `semantic' names (<person> person stuff </person>)
• still Hyperlinks: http://computer/directory/file+/entrypoint$ (see Regular expression syntax)
• optional metadata for description (DTD) and/or presentation (XSL)

Read more in XML intro.

XML tags are business domain dependent. Domains might be:

• Petroleum products trading
• Shakespeare plays (see examples in XML intro. )
• Household stuff (for manufacturers to stores)
• office supplies (for the Friday afternoon task of ordering stuff)
• . . . suggest more . . .

For each domain the allowable tags, and the structure in which they appear has to be defined. That is done in a Data Tag Definition (DTD). To indicate if elements are optional, or can be repeated they are labeled with characters used in Regular Expressions.

Regular expression syntax

Important for formulating representation grammars and queries (getting some subset of the representation)

1. sequence: (a,b,c)

2. alternatives: (x|y), in combination (x|y, b,c) {x,b,c or y, b, c}

3. optional: q? = {q | nothing}

4. repeats any number of times: r* {nothing | r | rr | rrr | rrr... }

5. repeats one more times : s+ { s | ss | sss | sss... }

Example:
(((S|s)ection|paragraph(s$) )*.)
matches all citations looking like
Section xx., section xx., paragraph xx., paragraphs xx.
By setting a marker for xx, those text can be retrieved for display or processing. A regular language is capable, but not really user-friendly.

• Would such a query language help your browsing?
• Would such a language help in screen-scraping?

XSL

To look at an XML file it must be transformed, best to HTML. Examples are given in the XML description.
For instance an XML catlog with entries as <Product> <Name>Pencil </Name> <Quantity>12 </Quantity> <Price>1.50 </Price> <Weight>60 </Weight> <Color> yellow </Color> </Product>
ETC

Would be instructed through an XSL program to

1. Put a heading in " ITEM (boxed), Quantity/box , Price per box , ...
2. Start a new line whenever a <Product> tag appears
3. put a dollar sign in front of price
4. put gram behind </Weight>

for a U.S. customer divide the number by 32? and put oz. behind </Weight> <

5. Perhaps add a java routine to compute a total at the end, when the customer clicks [done]

References

Brief intro to XML.
0 Brief intro to RDS ADO [ASP, 25Feb 2000].
XSL information
See also the references. 

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Standards

High value to businesses, especially if theirs get accepted. Increases efficiency overall, levels the playing field for sll and large companies.

Alternate means of developing standards

Implement, show, convince others of usefulness; much leverage if major company (now Microsoft, formerly IBM)

Committee of wise men, supported government mandates.

Governments can set standards, but are rarely competent to do so. Politicians and marketers think it's simple, like electric plugs.

Commercial value of getting one's standard accepted. Standards are a major commercial competitive weapon.

Now we have a surfeit of standards (look at video storage), confusion, cost, dirty tricks.

Standards take long to develop, criticize, implement, get the bugs out.

Then they stick around for a long time, often too long.

Two-horse Roman chariot -> grooves in limestone street --> all carts --> mines --> steam-propelled mine carts -> RRs -> Bullet Trains in Japan.

Notes

See BRittania Website [Computerworld July 2000] article.