SGML View of the World: Structure, Content, and Format

1
SGML View of the World Structure, Content, and
Format
2
Schedule

• How SGML views document (structure, content, and
  format)
• Why this view is important
• HOW SGML works with this view

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Structure, Content, and Format

• Central to SGML is the concept that documents
  have structure, content, and format.
• These three ingredients combine to form a
  document.
• They interrelate in subtle ways, and you can
  easily confuse them as you work with your
  documents.

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What is Structure?

• The structure defines how the document is laid
  out and in what order elements are assembled
• For example, a bicycle assembly manual might
  consist of of the following section in this
  order an introduction that described the
  document and lists the manufacturers address,
  assembly instructions, a part list, instruction
  for order replacement parts, troubleshooting
  advice, and index.

5
What is Structure?

• When create a document with a word processor, the
  structure is implied.
• SGML requires the author to define a document
  structure explicitly ahead of time.

6
What is Content?

• Content is the actual data within a document.
• The words and illustrations that make up a
  bicycle assembly manual are its contents.

7
What is Format?

• Format consists of how the words, sentences, and
  paragraphs are visually presented and
  distinguished from one another within a document.
• Boldface for title, italics for special terms,
  and blank lines between sections are examples of
  document formats.

8
What is Format?

• People often confuse format with structure.
• This is because structure is commonly implied
  within word processors through the use of
  specialized, tailored formatting called style.

9
Why Structure, Content, and Format Are Important
in SGML?

• SGML provides a mechanism for delivering
  documents or structural information in a number
  of ways, including a mechanism for delivering the
  same content and structure through different
  programs, formats, and delivery media.
• To do this efficiently, SGML must define the
  structure and separate the content from the
  delivery-specific format.
• Through this approach, the actual document its
  content and structure becomes mobile.

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Indicating Structure Through Visual Cues

• PRODUCT ADVISORY
• Number 146
• Type Parts
• Date 8/15/95
• Subject Revised Replacement Parts ...
• Model 501 User Replaceable Parts
• The parts list identified in the AnyCorp Model
  501 ...
• New Parts List
• 1. 345-234 (Filter, cooling fan)
• 2. 148-745 (Fuse, power 1.5amp)
• 3 ...

• Product Advisory
• Number 146
• Type Parts
• Date 8/15/95
• Revised
• Subject Revised Replacement ...
• Model 501 User-Replaceable Parts
• The parts list identified in the ...
• New Parts List
• 1. 345-234 (Filter, cooling fan)
• 2. 148-745 (Fuse, power 1.5amp)
• 3. ...

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Losing Structure in Word Processing Document

• By specifying document structure through
  formatting hints, you become dependent on format.
  
• What happen if you lose this format?
• That might occur when you translate a highly
  structured document from one word-processing
  format to another. The text will likely translate
  correctly, but the formatting might translate
  less accurately.
• If this translation process is particularly
  troublesome, the formatting might end up in a
  jumble, making the document extremely difficult
  to read.
• Important parts of the structures could be lost.

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Structural Views of Information

• Now consider the product advisory bulletin from a
  structural perspective.
• Product advisory
• Identification number
• Advisory type
• Date
• Revision date
• Subject
• Body
• Subsection
• Title
• List
• Subsection
• Title
• List
• This is how SGML looks at documents.

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Defining Structures in SGML

• The structure of a document ? its type ? is
  defined by a document type definition, or DTD.
• The DTD lays out the rules for a document through
  the use of elements, attributes, and entities.

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Defining Structures in SGML

• lt!DOCTYPE advisory
• lt!ENTITY parael parablistnlistgraphicgt
• lt!ELEMENT advisory - - (idinfo,subject,subsec)gt
• lt!ELEMENT idinfo - - (advnbr,type,dateiss,datere
  v,product)gt
• lt!ELEMENT subject - - (PCDATA)gt
• lt!ATTLIST subject safty (yn) ngt
• lt!ELEMENT subsec - - (title,(parael)?)gt
• lt!ELEMENT advnbr - - (PCDATA)gt
• lt!ELEMENT type - - (PCDATA)gt
• lt!ELEMENT dateiss - - (PCDATA)gt
• lt!ELEMENT daterev - - (PCDATA)gt
• lt!ELEMENT product - - (PCDATA)gt
• lt!ELEMENT title - - (PCDATA)gt
• lt!ELEMENT para - - (PCDATA)gt
• lt!ELEMENT blist - - (item) -(nlist)gt
• lt!ELEMENT nlist - - (item)gt
• lt!ELEMENT item - - (parablistnlistgraphic
  PCDATA)gt
• lt!ELEMENT graphic - 0 EMPTYgt
• lt!ATTLIST graphic filename CDATA REQUIRED

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Using Structures in SGML

• lt!DOCTYPE ADVISORY PUBLIC "advisory" "advisory"gt
• ltADVISORYgtltIDINFOgtltADVNBRgtNumber 146lt/ADVNBRgt
• ltTYPEgtType 146lt/TYPEgt
• ltDATEISSgtDate 8/15/95lt/DATEISSgt
• ltDATEREVgtRevised 9/29/95lt/DATEREVgt
• ltPRODUCTgtModel 501 Nebulationlt/PRODUCTgtlt/IDINFOgt
• ltSUBJECTgtSubject Revised Replacement Parts List
  (AnyCorp Model 501)lt/SUBJECTgt
• ltSUBSECgtltTITLEgtModel 501 User-Replaceable
  Partslt/TITLEgt
• ltPARAgtThe parts list identified in the AnyCorp
  Model 501 User's Maintenance Guide has been
  superseded, effective immediately.
  User-Replaceable parts are identified in the
  revised part list below. Parts orders which
  reference items o15n the previous list (dated
  2/5/94) will be honored up to 3/14/96.
• Customers are advised to order from this revised
  list in order that they may achieve higher
  reliability at a lower unit cost. Questions on
  this subject should be directed to the Central
  Spares Organization.lt/PARAgtlt/SUBSECgt
• ltSUBSECgtltTITLEgtNew Parts Listlt/TITLEgt
• ltBLISTgtltITEMgt345-234(Filler, coolingfan)lt/ITEMgt
• ltITEMgt148-745(Fuse, power, 1.5amp)lt/ITEMgt
• ltITEMgt345-712(Lamp, Indicator)lt/ITEMgt
• ltITEMgt2346-92(Disk, cleaning)lt/ITEMgt
• ltITEMgt347-622(Swabs, cleaning)lt/ITEMgtlt/BLISTgtlt/SUB
  SECgtlt/ADVISORYgt