Worshipping at the Shrine

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					     Worshipping at the Shrine:

Myths and Legends from comp.text.xml

  Kerry “the heretic” Raymond, CiTR

        <kerry@citr.com.au>
        <kerry@dstc.edu.au>
              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
        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.”
 So inadequate, please extend it?

• XML 1.0 not enough
  –   XML Namespaces
  –   XML Schema
  –   XML Data
  –   XML Link
  –   XML Pointer
  –   And so on …
                          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
                    Ancient Myths:
        when 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
                 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
     • <longtagname> … </longtagname>
  – 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)
                       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.
                Myth: XML will replace
                       word 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
                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
 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
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
                            What XML isn’t!

•   Compact
•   Fast
•   A program of any sort
•   A communications protocol
•   A solution to interoperability problems
    – But it can help in lots of ways
             New Myths about XML!
• We need to define specialised network
  protocols for it
  – What’s 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
            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.”
              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.”
     Conclusions on XML



        Use it
      Abuse it
Just don’t worship it!

				
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posted:7/30/2012
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