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XML and NNF

XML and NNF. A Standard Form for XML Documents (XNF) Properties As few hierarchical trees as possible No redundant data values in any tree Method Model the application as a hypergraph of functional and multi-valued constraints. Make the hypergraph canonical.

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XML and NNF

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  1. XML and NNF • A Standard Form for XML Documents (XNF) • Properties • As few hierarchical trees as possible • No redundant data values in any tree • Method • Model the application as a hypergraph of functional and multi-valued constraints. • Make the hypergraph canonical. • Transform the canonical hypergraph into an NNF scheme-tree forest with as few trees as possible. • Cast the NNF scheme trees into XML DTD / Schema.

  2. XNF Example NNF with as few schemes as possible: FD Closures: NrBeds: 4, Cost: 4, RoomNr: 3, RoomName: 3, GuestName: 2, View: 1, GuestNr: 1. Back off by one, when possible. Result: (RoomNr, RoomName, Cost, NrBeds, (View)*, (GuestNr, GuestName)* )*

  3. DTD(Document Type Definition) • Defines a structure for XML documents • Declarations • DOCTYPE • ELEMENT • Structural elements in terms of regular expressions (, * + ? |) • Elementary elements as Parsable Character DATA (#PCDATA) • ATTLIST

  4. Straightforward Translation • Main Idea: Use the scheme-tree forest directly as the DTD specification. • Details: • Introduce a root name (e.g. <!DOCTYPE BandB [ … ]>). • Rename attributes appearing in multiple trees. • Add the scheme trees as structural elements (e.g. <!ELEMENT BandB ((RoomNr, RoomName, … )*)>). • Declare all attributes as elements with character data (e.g. <!ELEMENT RoomNr (#PCDATA)>).

  5. Example (RoomNr, RoomName, Cost, NrBeds (View)* (GuestNr, GuestName)* )* <!DOCTYPE BandB [ <!ELEMENT BandB ( ( RoomNr, RoomName, Cost, NrBeds, (View)*, (GuestNr, GuestName)* )*)> <!ELEMENT RoomNr (#PCDATA)> <!ELEMENT RoomName (#PCDATA)> … <!ELEMENT GuestName (#PCDATA)> ]> <BandB> <RoomNr>1</RoomNr> <RoomName>Kennedy</RoomName> <Cost>90</Cost> <NrBeds>2</NrBeds> <View>Forest</View> <View>Sea</View> <GuestNr>101</GuestNr> <GuestName>Smith</GuestName> <RoomNr>2</RoomNr> … </BandB>

  6. A More Sophisticated Translation • Main Idea: Nest the XML according to the scheme-tree structure • Details • Create concept names for each node (e.g. Rooms). • Identify key elements for nodes (e.g. RoomNr). • Nest according to node names and key elements (e.g. <!ELEMENT Rooms (RoomNr)*>). • Use XML attributes for key elements (e.g. <!ATTLIST RoomNr value CDATA #REQUIRED>).

  7. Example Rooms: RoomNr, RoomName, Cost, NrBeds Views: View Guests: GuestNr, GuestName <!DOCTYPE BandB [ <!ELEMENT Rooms (RoomNr)*> <!ELEMENT RoomNr (RoomName, Cost, NrBeds, Views, Guests)> <!ATTLIST RoomNr value CDATA #REQUIRED> <!ELEMENT RoomName (#PCDATA)> <!ELEMENT Cost (#PCDATA)> <!ELEMENT NrBeds (#PCDATA)> <!ELEMENT Views (View)*> <!ELEMENT View EMPTY> <!ATTLIST View value CDATA #REQUIRED> <!ELEMENT Guests (GuestNr)*> <!ELEMENT GuestNr (GuestName)> <!ATTLIST GuestNr value CDATA #REQUIRED> <!ELEMENT GuestName (#PCDATA)> ]> <BandB> <Rooms> <RoomNr value=“1”> <RoomName>Kennedy</RoomName> <Cost>90</Cost> <NrBeds>2</NrBeds> <Views> <View value=“Forest”/> <View value=“Sea”/> </Views> <Guests> <GuestNr value=“101”> <GuestName>Smith</GuestName> </GuestNr> </Guests> </RoomNr> <RoomNr value=“2”> … </Rooms> …

  8. A Translation to XML Schema • XML Schema supersedes DDT’s • Adds data types • Adds keys and uniqueness constraints • Adds power to cardinality constraints • … • Same basic idea as the sophisticated translation: use keys and nest according to the structure • Generate names automatically • Add cardinality and uniqueness constraints

  9. Example RoomNr, RoomName, Cost, NrBeds View GuestNr, GuestName <xs:element name=“RoomNrs”> <xs:complexType> <xs:sequence> <xs:element name=“RoomNr” minOccurs=“1” maxOccurs=“unbounded”> <xs:complexType> <xs:all> <xs:element name=“Views”> … </xs:element> <xs:element name=“GuestNrs”> … </xs:element> </xs:all> <xs:attribute name=“RoomNr” use=“required”> … <RoomNrs> <RoomNr RoomNr=“1” RoomName=“Kennedy” NrBeds=“2” Cost=“90”/> <Views> <View View=“Forest”/> <View View=“Sea”/> </Views> <GuestNrs> <GuestNr GuestNr=“101” GuestName=“Smith”/> … </RoomNrs> (Full XML-Schema Instance)

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