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Semantic Objects

Learn the definitions, cardinality, paired attributes, identifiers, object types, and transformations of semantic objects in data modeling. Understand the attributes and classes associated with semantic objects and their representation.

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Semantic Objects

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  1. Semantic Objects

  2. Definitions • A semantic object is a named collection of attributes that sufficiently describes a distinct identity • Semantic objects are grouped into classes each of which has a name • A semantic object has a collection of attributes • Objects represent distinct identities that users recognize as independent and separate and that they want to track and report

  3. More definitions • Simple attributes have a single element • Group attributes are composites of other attributes • Semantic object attributes are attributes that establish a relationship between one semantic object and another

  4. Example to consider • What are the simple attributes? • What are the group attributes? • What are the semantic object attributes?

  5. Attribute Cardinality • Each attribute has a minimum cardinality • ususally 0 or 1 • Each attribute has a maximum cardinality • usually 1 or n • Cardinalities are shown in format n.m where • n is the minimum cardinality and • m is the maximum cardinality • Cardinalities of groups and attributes of groups can be subtle

  6. Example • What is the minimum cardinality of CampusAddress? • What is the minimum cardinality of Building? • Note: cardinalities operate only between the attribute and the container of the attribute.

  7. Object Instance

  8. Paired Attributes • THERE ARE NO ONE-WAY OBJECT RELATIONSHIPS. • IF AN OBJECT CONTAINS ANOTHER OBJECT, THEN THE SECOND OBJECT WILL CONTAIN THE FIRST.

  9. More definitions • An object identifier is one or more object attributes that the users employ to identify object instances. • A group identifier is an identifier that has more than one attribute • The domain of an attribute is a description of the attribute’s possible values • The domain of a simple attribute consists of both a physical and a semantic description • The domain of a group attribute also consists of both a physical and a semantic description

  10. Still more definitions • The portion of an object that is visible to a particular application is called the semantic object view or simply the view.

  11. Types of Attributes • Necessary to describe types of objects • A single-value attribute is an attribute whose maximum cardinality is one • A multivalue attribute is one whose maximum cardinality is greater than one • A nonobject attribute is a simple or group attribute

  12. Types of Objects • Simple • Composite • Compound • Hybrid • Association Objects • Parent Subtype Objects • Archetype/Version Objects

  13. Simple Objects • A simple object is a semantic object that contains only single-value, simple or group attributes.

  14. Transformation of Simple Object

  15. Composite Objects • A composite object is a semantic object that contains one or more multivalue simple or group attributes but no object attributes.

  16. Transformation of a Composite Object

  17. Transformation of a Composite Object - separate group attributes

  18. Transformation of a Composite Object - nested group attributes

  19. Compound Objects 1:1 • A compound object contains at least one object attribute.

  20. Transformation of a Compound Object – 1:1

  21. Transformation of a Compound Object – 1:1 – Two ways

  22. Compound Objects 1:N or N:1

  23. Transforming a Compound Object 1:N or N:1

  24. Compound Objects N:M

  25. Transformation of Compound Objects N:M

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