Introduction into InstantView^® Scripting

Thirty different Window Objects currently form the visible part of InstantView^®. These window objects contain Action Lists to define application dynamics as a reaction to an event. There are System Events and freely defined Messages (these messages are an important software instrument to form independent Modules by structuring complex applications).

The simple language InstantView^®Script defines Windows resources and activities. It has been developed, so even non-professionals can work with model objects. InstantView^®(Script) is easy to understand and easy to use. In this way comparable to BASIC. Straight and simple solutions rather than elegant and complicated:

• There are no type declarations. Variables work like a container which can keep numbers, strings, objects etc.. InstantView^® makes sure, operations can only be executed accurately - and generates a problem report if required. If one of the arithmetic operators +. -, * and / are apply to an object, the object needs to decide, whether the operation is reasonable or if it gets rejected.

• Logically connected values (objects, numbers, strings) can be pooled in a Vector.

• Statements have maximum two constant parameters to specify a required operation. Variable parameters are mediated via stack. The statement result is put into the stack. The stack elements are the same containers that are used for Variables. Why a stack? First: it's a very simple concept. Someone who has never done any computer programming before can easily figure an InstantView^® statement as a machine that first takes something out of the stack (always from the top!), executes the required task and then writes the result into the remaining stack. One disadvantage is the postfix notation. To add a and b, the operation must be written as follows: a b +, not as usually a + b. This is important, since '+' takes both operands out of the stack and then puts the result into the stack. Complex arithmetic expressions should be calculated inside the object member function, though. The constantly changing stack needs to be considered at all times. This can become annoying when keeping provisional results across several statements. But that's what variables are for! A bit less obvious are the following stack architecture advantages: sub-programs in InstantView^® are user-defined statements - certainly a better concept than the GOSUB method in BASIC, but - just like BASIC - without needing to deal with parameter transfer  (call by value versus call by reference). InstantView^® Message Passing combined with the stack mechanism allow for an easy data transfer via message.

• There are the known constructs to structure a program (locally): Alternative (if, else), Cycle Creation (do, while, loop), Selection (case) and Composition (User-Defined Statements).

• Modules divide larger applications. Each module creates its own namespace for Variables and User-Defined Statements. Modules hold all characteristics of object-orientation:

• Encapsulation: Different modules communicate via Messages, which are forming the module interface to the outside world. To join modules, only accepted messages have to be known.

• Inheritance: Further modules can be derived from one module. The derived module inherits all window resources and activities from the base module, to complement them or to overwrite them via redefinition. 

• Polymorphism: All inherited activities are polymorph (analog virtual functions in C++).

Modules are software building blocks on the highest level of abstraction. They can be immediately used to build an application. External Module Definitions have been introduced to support large applications.

Intelligent Mapping Between Window- and Model Objects controls data exchange between model and interface. Model data visualization becomes simple and efficient (FillWindow, DrainWindow). An Access Path describes the connection between view and model and can be used to track relations and call functions.

Most InstantView^® model classes are also capable of holding dynamic data - Slots, other than just data that has been statically defined via C++ class definition. InstantView^® makes the Slots appear like 'normal' data members. Slots can appear in an Access Path, or they can be used in a Query formulation. The mapping between model and interface considers, that a slot is not necessarily existent in all class instances (Volatile Window Objects).

InstantView^® is an interpreter. Applications that have been described with InstantView^®Script, are translated into a format which can be interpreted very quickly. 

An application interface is usually built interactively with the ClassiX^® WorkBench. The workbench automatically generates the according InstantView^®Script files. The generated code can be processed in a text editor at any stage.