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An abstract is the entire summary of something.
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What does abstaction mean?
1. a concept or idea not associated with any specific instance2. a sketchy summary of the main points of an argument or theory
What is abstaction in java?
The concept of abstraction is concept talked about when talking about inheritance. When you make a class abstract, it means that the class is a general "abstract" idea, not something you want to instantiate (create an object from.) However, abstract classes are useful for when you want to create real sub-classes of the abstract class. For example, you could have an abstract class named "animal" that had the general characteristics of all animals, then you can have regular sub-classes that inherit "animal", like "dog", "cat" or "horse." The reason for making the "animal" class abstract is to make sure that one can't create a generic "animal" object, but so they can create objects that inherit the idea of "animal."
What is the difference between schema and database?
Database schema are the logical structure of entities (tables or object classes) and their relationships (keys, or object associations) in a database. Schema can exist at different levels of abstraction (see: en.wikipedia.org/wiki/Database_schema). Schema themselves may or may not exist as such in a database. In general schema at the higher levels of abstraction are design models that are captured in printed documents, and authored by business analysts and database designers, rather than created by database programmers and stored in the database itself. But in some types of databases, schema at any level of abstaction can be realized physically. In Oracle databases, schema can be realized as schema objects, which are a part of an Oracle database. These schema objects may represent a human user's conceptual model of the knowledge captured in an enterprise database. Thus defined, there can be many schema that can be associated with one physical database. In other kinds of relational database, an abstract user's schema can be represented by logically linked metadata, views, and stored procedures assocated with a user class. In object-oriented databases, especially those based on the highly self-referential language Smalltalk (e.g. Gemstone/S), schema are realized as "physical" objects in the database as a matter of course, as well as in the logical models captured in design documents. The schema objects in such databases are, in essence, the classes comprising the infrastructure of the database or application. Oracle-style user schema are readily created; these would be realized as user interface orchestrator classes.
