Remote incremental program verification using API definitions

Details Remote incremental program verification using API definitions Remote incremental program verification using API definitions

2000-09-14

2003-11-18

Iqbal, Nadeem (Department: 2184)

Error detection/correction and fault detection/recovery

Data processing system error or fault handling

Reliability and availability

C717S135000

Reexamination Certificate

active

06651186

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to computer systems. More particularly, the present invention relates to a system and method for remote distributed program verification using API definitions.
2. Background
In general, computer programs are written as source code statements in a high level language that is easy for a human being to understand. As the computer programs are actually executed, a computer responds to machine code, which consists of instructions comprised of binary signals that directly control the operation of a central processing unit (CPU). A special program called a compiler is typically used to read the source code and to convert its statements into the machine code instructions of the specific CPU. The machine code instructions thus produced are platform dependent, that is, different computer devices have different CPUs with different instruction sets indicated by different machine codes.
More powerful programs are typically constructed by combining several simpler programs. This combination can be made by copying segments of source code together before compiling and then compiling the combined source. When a segment of source code statements is frequently used without changes, it is often preferable to compile it once, by itself, to produce a module, and to combine the module with other modules only when that functionality is actually needed. This combining of modules after compilation is called linking. When the decision on which modules to combine depends upon run time conditions and the combination of the modules happens at run time, just before execution, the linking is called dynamic linking.
Object Oriented Principles
Object oriented programming techniques such as those used by the Java™ platform are widely used. The basic unit of object oriented programs is an “object”. An object has methods (procedures) and fields (data). The term “members” is used herein to refer to methods and fields. A method declares executable code that can be invoked and that passes a fixed number of values as arguments. A class defines the shared members of the objects. Each object then is a particular instance of the class to which it belongs. In practice, a class is a template to create multiple objects (multiple instances) with similar features.
One property of classes is encapsulation. Encapsulation is used to describe a system wherein access to an object is provided through a public Application Programming Interface (API), while keeping the details private. In other words; the actual implementation of the members within the class is hidden from an outside user and from other classes, except as exposed by an API. This makes classes suitable for distributed development, for example by different developers at different sites on a network. A complete program can be formed by assembling the classes that are needed, linking them together, and executing the resulting program.
Classes enjoy the property of inheritance. Inheritance is a mechanism that enables one class to inherit all of the members of another class. The class that inherits from another class is called a subclass; the class that provides the attributes is the superclass. Symbolically, this can be written as subclass<=superclass, or superclass=>subclass. The subclass can extend the capabilities of the superclass by adding additional members. The subclass can override a virtual method of the superclass by providing a substitute method with the same name and type.
The members of a class type are fields and methods; these include members inherited from the superclass. The class file also names the superclass. A member can be public, which means that it can be accessed by members of the class that contains its declaration. A member can also be private. A private field of a class is visible only in methods defined within that class. Similarly, a private method may only be invoked by methods within the class. Private members are not visible within subclasses, and are not inherited by subclasses as other members are. A member can also be protected.
An interface type is a type whose members are constants and abstract methods. This type has no implementation, but otherwise unrelated classes can implement it by providing implementations for its abstract methods. Interfaces may have sub-interfaces, just as classes may have subclasses. A sub-interface inherits from its super-interface, and may define new methods and constants as well. Additionally, an interface can extend more than one interface at a time. An interface that extends more than one interface inherits all the abstract methods and constants from each of those interfaces, and may define its own additional methods and constants.
Java™ Programming Language
In the Java™ programming language, classes can be grouped and the group can be named; the named group of classes is a package. If a class member is not declared with any of the public, private or protected keywords, then it is visible only within the class that defines it and within classes that are part of the same package. A protected member may be accessed by members of declaring class or from anywhere in the package in which it is declared. The Java™ programming language is described in detail in Gosling, et al., “The Java™ Language Specification”, August 1996, Addison-Wesley Longman, Inc.
Java™ Virtual Machine
Programs written in the Java™ language execute on a Java™ virtual machine (JVM), which is an abstract computer architecture that can be implemented in hardware or software. Either implementation is intended to be included in the following description of a VM. For the purposes of this disclosure, the term “processor” may be used to refer to a physical computer or a virtual machine.
A virtual machine is an abstract computing machine generated by a software application or sequence of instructions that is executed by a processor. The term “architecture-neutral” refers to programs, such as those written in the Java™ programming language, which can be executed by a virtual machine on a variety of computer platforms having a variety of different computer architectures. Thus, for example, a virtual machine implemented on a Windows™-based personal computer system will execute an application using the same set of instructions as a virtual machine implemented on a UNIX™-based computer system. The result of the platform-independent coding of a virtual machine's sequence of instructions is a stream of one or more bytecodes, each of which is, for example, a one-byte-long numerical code.
The Java™ Virtual Machine (JVM) is one example of a virtual machine. Compiled code to be executed by the Java™ Virtual Machine is represented using a hardware- and operating system-independent binary format, typically stored in a file, known as the class file format. The class file is designed to handle object oriented structures that can represent programs written in the Java™ programming language, but may also support several other programming languages. These other languages may include, by way of example, Smalltalk, C and C++. The class file format precisely defines the representation of a class or interface, including details such as byte ordering that might be taken for granted in a platform-specific object file format. For the sake of security, the Java™ Virtual Machine imposes strong format and structural constraints on the instructions in a class file. In particular example, JVM instructions are type specific, intended to operate on operands that are of a given type as explained below. Any language with functionality that can be expressed in terms of a valid class file can be hosted by the Java™ Virtual Machine. The class file is designed to handle object oriented structures that can represent programs written in the Java™ programming language, but may also support several other programming languages. The Java™ Virtual Machine is described in detail in Lindholm, et al., “The Java™ Virtual Machine Specification”, April 1999, Addison-Wesley Long

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