Pertemuan 13 Object Query Language

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Pertemuan 13Object Query Language

• Matakuliah M0174/OBJECT ORIENTED DATABASE
• Tahun 2005
• Versi 1/0

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Learning Outcomes

• Pada akhir pertemuan ini, diharapkan mahasiswa
• akan mampu
• Mahasiswa dapat Menghasilkan query language dalam
  object data model (C3)

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Outline Materi

• Overview OQL
• Accessing literal and named objects
• Accessing object values
• Accessing characteristics of object

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Overview OQL

• OQL is an object database query language, and is
  specified as part of the ODMG.
• OQL can also be classified as an object database
  sub-language in that its scope is limited to
  performing just one aspect of object database
  applications, e.g the sort of queries and
  manipulations that can be expressed in the object
  algebra

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Overview OQL

• A particular limitation is that OQL cant express
  arbitrarily complex computations, so OQL is not
  computation complete.
• It is therefore necessary to use OQL in
  conjunction with other computer languages
• OQL is used to describe the retrieval and
  manipulation of object.
• The ODL define interface to object type used by
  the OQL code.

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Overview OQL

• Other programming language, such as C, Java are
  used to implement object operations e.g methods
• Other programming language (C,Java) are used to
  implement application program, with embedded OQL
  statements to manipulate the object database

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Overview OQL

• OQL can be used for both collection-oriented and
  navigational queries
• A collection-oriented query retrieves a
  collection of objects - The way in which those
  objects are located is the responsibility of the
  ODBMS, rather than the application program.
• Navigational queries access individual objects
  and use object relationships to navigate from one
  object to another it is the responsibility of
  the applications program within which the OQL is
  embedded to specify the navigation procedure for
  accessing all object of interest.

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Overview OQL

• The designer of OQL have adopted an evolutionary
  approach. Rather than designing a completely new
  language, they have based OQL on SQL.
• Many query in SQL are also valid in OQL, though
  sometimes with minor change. However OQL also
  extends SQL to deal with object-oriented notation
  and operation invocation

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Accessing literal and named objects

• The simplest form of OQL query is an object name.
• Object names are used as entry points into an
  object database
• Example

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Accessing object values

• Dereferencing
• Example

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Accessing characteristics of object

• An object name can be used, in conjunction with
  the names of object characteristics (attributes,
  relationships, and operations) to access the
  individual characteristics of the named object or
  of others related to it
• Path
• Example

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SUMMARY

• OQL can define objects of interest using object
  names and literal values as entry points into an
  object database.
• The simplest form of OQL query is a name or
  literal value
• Paths are used to access object characteristics
  and related object.
• Queries can access objects
• Alternatively, by preceding a query with an
  asterisk, it an access object values