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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 an ORM. Make the ORM 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 an ORM. • Make the ORM canonical. • Transform the canonical ORM into an NNF scheme-tree forest with as few trees as possible. • Cast the NNF scheme trees into XML DTD.

  2. XNF Example NNF with as few schemes as possible: FD Closures: NrBeds: 4, Cost: 4, RoomNr: 3, RoomName: 3, GuestName: 2 Back off by one. 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 object-set names appearing in multiple trees. • Add the scheme trees as structural element (e.g. <!ELEMENT BandB ((RoomNr, RoomName, … )*)>). • Declare all object sets 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 objects (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 Rooms [ <!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 (#PCDATA)> <!ELEMENT Guests (GuestNr)*> <!ELEMENT GuestNr (GuestName)> <!ATTLIST GuestNr value CDATA #REQUIRED> <!ELEMENT GuestName (#PCDATA)> ]> <Rooms> <RoomNr value=“1”> <RoomName>Kennedy</RoomName> <Cost>90</Cost> <NrBeds>2</NrBeds> <Views> <View>Forest</View> <View>Sea</View> </Views> <Guests> <GuestNr value=“101”> <GuestName>Smith</GuestName> </GuestNr> </Guests> </RoomNr> <RoomNr value=“2”> … </Rooms>

  8. Additional Translations • No unique solution • Correspondences for additional ORM features • Roles: role attributes (e.g. role=“Current Guest”) • Optionals: zero or one occurrence (e.g. Room (Occupant?)) • Partitions: U (e.g. (OccupiedRoom | UnoccupiedRoom)) • Each translation maintains the properties of XNF • As few scheme trees as possible • No potential redundancy +

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