Worshipping at the Shrine:

1
Worshipping at the Shrine

• Myths and Legends from comp.text.xml
• Kerry the heretic Raymond, CiTR
• ltkerry_at_citr.com.augt
• ltkerry_at_dstc.edu.augt

2
XML is the new religion

• Why is XML so popular?
• No new idea, but a simple SGML
• Right place at the right time
• HTML introduced mark-up to a wide audience
• W3C brandname
• worse is better or simple better than perfect
• Lots of XML-enabled products announced

3
So simple, anyone can do it!

• I am a 45yr old medical Doctor (General
  Practice, England) who needs the challenge of a
  new career. Electronics/communications/computing
  have been a lifetime hobby interest.
• I propose to learn XML etc. and combine this with
  my people skills to work personally with
  customers to provide them with information
  management solutions, specialising in medical
  environments.

4
So inadequate, please extend it?

• XML 1.0 not enough
• XML Namespaces
• XML Schema
• XML Data
• XML Link
• XML Pointer
• And so on

5
What XML is?

• XML is a data format with a basic syntax and
  generic well-formedness rules
• DTD and Schema provide model-specific
  well-formedness rules
• Semantics of the model
• Out of scope!
• Often confused with related APIs and tools, e.g.
  DOM

6
Ancient Mythswhen comp.text.xml was new

• XML is compact
• XML is fast
• XML will replace word processors
• XML will replace relational databases
• XML will replace CORBA
• XML-enabled applications will interwork

7
Myth XML is Compact

• XML is bigger than most proprietary format (for
  the same information content)
• Content presented as text not binary
• Markup is verbose
• ltlongtagnamegt lt/longtagnamegt
• Lots of nesting but little content
• Often more bytes in tags than in content
• But does it matter?
• Only if short of space (e.g. floppy disk)

8
Myth XML is fast

• How do you measure the speed of a data format
  anyway?
• Being both generic and heavily text-based
  (requiring lexical analysis and parsing),
  specialised binary formats will be faster
• Development of an XML-enabled tool is faster (XML
  parser is a generic COTS tool)
• Does it matter? Depends on your application.

9
Myth XML will replaceword processors

• A word processor is a program, not a data format
• XML is about semantic markup, word processors are
  mostly about presentation
• Word processors may use XML in addition to
  proprietary formats
• But interchange will require an agreed DTD/schema
• Interchange will address presentation not
  semantics
• Word processors may enable embedding of XML tags
  and become XML editors

10
Myth XML will replace relational databases

• While XML can express the content of a
  (relational) database, it is not an efficient
  format for either query or update
• Could build a database engine based on XML but
  performance will be an issue
• Use of XML may replace the use of small static
  databases
• XML has a role for interchange
• But only if a DTD/schema is agreed

11
Myth XML will replace CORBA

• XML could be used as the underlying message
  format (invisible to CORBA users)
• But larger and slower than current format
• Could enable interaction with non-CORBA
  applications
• Provided they were CORBA-DTD/Schema compliant and
  responded according to CORBA protocol
• So not CORBA but very CORBA-aware!
• XML can be carried as CORBA payload
• but so can Shakespearean sonnets

12
Myth XML-enabled applications will interwork

• Yes, to the extent of parsing an XML file
• Yes, to doing generic actions on that file
• E.g. create a database with corresponding
  structure
• After that, you need semantic knowledge of the
  DTD/Schema (if any)
• E.g. update an existing database

13
What XML isnt!

• Compact
• Fast
• A program of any sort
• A communications protocol
• A solution to interoperability problems
• But it can help in lots of ways

14
New Myths about XML!

• We need to define specialised network protocols
  for it
• Whats wrong with SMTP, FTP, and HTTP?
• XML is not small enough nor fast enough!
• Driven by desire to use XML in applications in
  small mobile devices
• e.g. PDAs, mobile phones
• low bandwidth and limited computation

15
WBXML XML as binary

• The binary format was designed to allow for
  compact transmission with no loss of
  functionality or semantic information
• allowing more effective use of XML data on
  narrowband communication channels
• The binary format encodes the parsed physical
  form of an XML document, i.e., the structure and
  content of the document entities.

16
Disillusionment sets in

• Specifically I am complaining that W3C taking
  years and years to release XML schema including
  simple and obvious things like data types, which
  are desperately needed by small business.
• instead of meeting human needs, W3C includes an
  endless progression of enhancements that make XML
  too large and complex for production developers
  to economically traverse.
• the reason is corruption too many
  individuals in the process are motivated to keep
  making XML complex, delaying competitors uptake,
  and intentionally preventing the general
  population from using XML for data
  interoperability in business.

17
Conclusions on XML

• Use it
• Abuse it
• Just dont worship it!