say a few words before crap. Now is engaged in the object-oriented database in the domestic promotion work, if interested can contact me. If you have any questions you can send a private messages to me, you can also go to our site object-oriented database Exchange community to ask me questions, I will be the fastest speed to answer. want to make the object-oriented database Exchange community to become the country's largest object-oriented data exchange community, I hope that interested in working with me to operate this community, the following translation.
object-oriented databases are also known as Object Data management systems. Object databases store objects in object-oriented programming languages, such as Smalltalk,c++,java, and not just like relational databases, such as integers, strings, and real numbers. Objects are generally composed of the following parts:
--Properties: attributes quantify the characteristics of an object, which can be a simple integer, a string or a real number, or it can be a complex object.
--Method: The method is also commonly referred to as a procedure or function, which specifies the behavior of the object.
Therefore, the object contains executable code and data. Of course the object has other characteristics, such as whether a method or data can be obtained outside the object, but for our article to be easy to understand and apply to the object-oriented database, in this article we do not consider these. Another thing that needs to be mentioned is "class." Classes are used in object-oriented programming to specify which methods and data an object contains. Classes are like templates for objects. The class itself does not contain methods and data, but it specifies what methods and data to include in the object. The class is used during object creation. In object-oriented databases, classes are used to create parts of objects that are not stored in the database (such as methods of objects).
comparison with relational database
A relational database stores data in a two-dimensional table that contains rows and columns. Because relational database tables are "formatted," there is not much duplication of data. All columns depend on the primary key (the unique value in the column) to identify the column. You can use specific values for a specific column to get or change the value of a row.
In order to put objects in a relational table, it is necessary to use simple data such as strings, integers, and real numbers to describe this class. For example, to describe an aircraft, the aircraft wing will use a separate table to describe its size and other features, the fuselage is described by another table, propellers, tires, etc. are also used in separate tables, and so on.
It takes a lot of labor to break down complex information into simple information, which requires code completion.
Object Persistence
In a traditional database, the data that is manipulated in the program is temporary, and the data stored in the database is persisted (stored on a permanent storage device). In an object-oriented database, a program can manipulate temporary data and persisted data.
when to use object-oriented data
use object-oriented databases, especially many-to-many object relationships, if the program manipulates very complex data or the relative relationships of the data are more complex. It is best not to use an object-oriented database if your data has few links or if you have a large amount of data.
the object-oriented database is suitable for:
--Computer Aided modeling program (Computer aided software Engineering, CAD, Computer aided manufacturing)
--Multimedia program
--Project engineering software with time-varying
--Business software
Object-oriented database benefits
--The object does not require boxing and unpacking operations, saving programming and execution time.
--Reduced paging
--Easy navigation
--Better concurrency control-the hierarchy of objects may be locked.
--The data model is based on the real world.
--works well in a distributed architecture state.
--If the program is also object-oriented, you can reduce the amount of code.
The disadvantage of object-oriented database
-the object-oriented database is less efficient if the relationship between data and data is relatively simple.
--The relational table is easier to understand.
-late binding may slow down the access speed.
--There are more tools in the relational database.
--The standard of relational databases is more stable.
--rdbms Services and support are more stable and do not need to be changed.
Odbms Standard
--Object data Management group
--Object Database Standard ODM6.2.0 (ODM6.2.0)
--Object Query Language (Language)
--Object Query Language support SQL92 (OQL supports of SQL92)
How data is stored
different database providers use two basic methods to store data.
--Each object contains a unique ID and is defined as a subclass of a base class, using an inherited method to determine the animal.
-use virtual memory mapping to store and manage objects.
data transfer is based on an object-based or page (usually 4K).
----Original article:Http://www.comptechdoc.org/ind .... Html. If the translation is wrong, please correct me. This article is also published in HTTP://OOD.TSON.COM/ARTICLE/9, welcome comments.
Object-oriented database (oriented Databases)
