VDM-10 Language Manual

Chapter 14
Top-level Specification (VDM++ and
VDM-RT)
In the previous sections VDM constructs such as types, expressions, statements, functions and
operations have been described. A number of these constructs can constitute the definitions inside
a class definition. A top-level specification, or document, is composed by one or more class
definitions. Note that only in VDM-RT it is possible to have a system class.
Syntax: document = class | system ,{ class | system } ;
14.1 System (VDM-RT)
In order to be able to describe distributed systems in VDM-RT includes a notion of a system that
describes how different parts of the system modelled are deployed to different Core Processing
Units (CPUs) and communication busses connecting the CPUs together. Syntactically the system
is described exactly like ordinary classes described below in Section 14.2, except that the keyword
“system” instead of the keyword “class”.
Syntax:
system = ‘system’, identifier,
[ class body ],
‘end’, identifier ;
class body = definition block, { definition block } ;
definition block = type definitions
| value definitions
| function definitions
| operation definitions
| instance variable definitions
| synchronization definitions
| thread definitions ;
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