Using Caché Objects - InterSystems Documentation

1.2 Class Definitions and the Class Dictionary
Every class has a definition that specifies what members (properties, methods, etc.) it contains
as well as class-wide characteristics (such as superclasses). These definitions are contained
within the Caché Dictionary, which is itself stored within the Caché database.
1.2.1 Creating Class Definitions
You can create class definitions in many ways:
• Using Caché Studio. The primary means of working with Caché class definitions is with
the Caché Studio Development Environment.
• Using XML. Class definitions have an external, XML-based representation. Typically
this format is used for storing class definitions externally (such as in source control systems),
deploying applications, or simply for sharing code. You can also create new class
definitions programatically by simply generating the appropriate XML class definition
file and loading it into a Caché system.
• Using an API. Caché includes a set of class definition classes that provide object access
to the Class Dictionary. You can use these to observe, modify, and create class definitions.
• Using SQL DDL. Any relational tables defined by DDL statements are automatically
converted to equivalent class definitions and placed within the Class Dictionary.
In addition, Caché includes a set of tools (such as the Caché RoseLink connection to the
Rational Rose modeling tool) as well as Wizards (such as the Caché Activate Wizard) that
automatically create class definitions.
1.2.2 The Class Dictionary
Class Definitions and the Class Dictionary
Every Caché namespace contains its own Class Dictionary which defines the available classes
for that namespace. There is a special “CACHELIB” namespace, installed as part of Caché,
that contains the definitions and executable code for the classes of the Caché Class Library.
These classes are referred to as system classes and all have names that start with a “%”
character. (Strictly speaking, they have package names that start with “%” ).
Every Caché namespace is automatically configured so that its Class Dictionary, in addition
to containing its own classes, has access to the system class definitions and code within the
CACHELIB namespace. By this mechanism, all namespaces can make direct use of the
classes in the Caché Class Library.
Using Caché Objects 3