This paper presents a logic based approach to debugging Java programs. In contrast with traditional debugging we propose a debugging methodology for Java programs using logical queries on individual execution states and also over the history of execution. These queries were arrived at by a systematic study of errors in object-oriented programs in our earlier research. We represent the salient events during the execution of a Java program by a logic database, and implement the queries as logic programs. Such an approach allows us to answer a number of useful and interesting queries about a Java program, such as the calling sequence that results in a certain outcome, the state of an object at a particular execution point, etc. Our system also provides the ability to compose new queries during a debugging session. We believe that logic programming offers a significant contribution to the art of object-oriented programs debugging.
JIVE's @cite_1 @cite_9 (Java Interactive Visualization Engine) design is based on the following seven criteria: (1) depict objects as environment of method execution; (2) display object states at different levels of granularity; (3) provide a sequence diagram to capture the history of execution; (4) support forwards and backwards execution of programs; (5) support queries on the runtime state; (6) produce clear and legible drawings; (7) uses exiting Java technologies. JIVE interacts with the JPDA to extract program trace. An on-line dynamic trace analysis is applied while the program runs for the first time in the forwards direction and postmortem trace analysis is applied in the backwards direction or in the forwards direction once program terminates.
@cite_9 @cite_1
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A novel approach to the runtime visualization and analysis of object-oriented programs is presented and illustrated through a prototype system called JIVE: Java Interactive Visualization Environment. The main contributions of JIVE are: multiple concurrent representations of program state and execution history; support for forward and reverse execution; and graphical queries over program execution. This model facilitates program understanding and interactive debugging. Our visualization of runtime states clarifies the important point that objects are environments of execution. The history of object interaction is displayed via sequence diagrams, and in this way we help close the loop between design-time and run-time representations. Interactive execution is made possible by maintaining a runtime history database, which may be queried for information on variable behavior, method executions, and object interactions. We illustrate the capabilities of this system through examples. JIVE is implemented using the Java Platform Debugger Architecture and supports the Java language and libraries, including multithreaded and GUI applications. We describe a novel approach to runtime visualization of object-oriented programs. Our approach features: visualizations of execution state and history; forward and reverse execution; interactive queries during program execution; and advanced drawing capabilities involving a combination of compile-time and runtime-analysis. Our methodology is realized in a software tool called JIVE, for Java Interactive Visualization Environment. Proof, verification and analysis methods for termination all rely on two induction principles: (1) a variant function or induction on data ensuring progress towards the end and (2) some form of induction on the program structure. The abstract interpretation design principle is first illustrated for the design of new forward and backward proof, verification and analysis methods for safety. The safety collecting semantics defining the strongest safety property of programs is first expressed in a constructive fixpoint form. Safety proof and checking verification methods then immediately follow by fixpoint induction. Static analysis of abstract safety properties such as invariance are constructively designed by fixpoint abstraction (or approximation) to (automatically) infer safety properties. So far, no such clear design principle did exist for termination so that the existing approaches are scattered and largely not comparable with each other. For (1), we show that this design principle applies equally well to potential and definite termination. The trace-based termination collecting semantics is given a fixpoint definition. Its abstraction yields a fixpoint definition of the best variant function. By further abstraction of this best variant function, we derive the Floyd Turing termination proof method as well as new static analysis methods to effectively compute approximations of this best variant function. For (2), we introduce a generalization of the syntactic notion of struc- tural induction (as found in Hoare logic) into a semantic structural induction based on the new semantic concept of inductive trace cover covering execution traces by segments, a new basis for formulating program properties. Its abstractions allow for generalized recursive proof, verification and static analysis methods by induction on both program structure, control, and data. Examples of particular instances include Floyd's handling of loop cutpoints as well as nested loops, Burstall's intermittent assertion total correctness proof method, and Podelski-Rybalchenko transition invariants. Preface. 1 Introduction. 1.1 Autonomous Agents. 1.2 Characteristics of Agents. 1.3 Multi-Agent Systems. 1.4 Hello World! 2 The BDI Agent Model. 2.1 Agent-Oriented Programming. 2.2 Practical Reasoning. 2.3 A Computational Model of BDI Practical Reasoning. 2.4 The Procedural Reasoning System. 2.5 Agent Communication. 3 The Jason Agent Programming Language. 3.1 Beliefs. 3.2 Goals. 3.3 Plans. 3.4 Example: A Complete Agent Program. 3.5 Exercises. 4 Jason Interpreter. 4.1 The Reasoning Cycle. 4.2 Plan Failure. 4.3 Interpreter Configuration and Execution Modes. 4.4 Pre-Defined Plan Annotations. 4.5 Exercises. 5 Environments. 5.1 Support for Defining Simulated Environments. 5.2 Example: Running a System of Multiple Situated Agents. 5.3 Exercises. 6 Communication and Interaction. 6.1 Available Performatives. 6.2 Informal Semantics of Receiving Messages. 6.3 Example: Contract Net Protocol. 6.4 Exercises. 7 User-Defined Components. 7.1 Defining New Internal Actions. 7.2 Customising the Agent Class. 7.3 Customising the Overall Architecture. 7.4 Customising the Belief Base. 7.5 Pre-Processing Directives. 7.6 Exercises. 8 Advanced Goal-Based Programming. 8.1 BDI Programming. 8.2 Declarative (Achievement) Goal Patterns. 8.3 Commitment Strategy Patterns. 8.4 Other Useful Patterns. 8.5 Pre-Processing Directives for Plan Patterns. 9 Case Studies. 9.1 Case Study I: Gold Miners. 9.2 Case Study II: Electronic Bookstore. 10 Formal Semantics. 10.1 Semantic Rules. 10.2 Semantics of Message Exchange in a Multi-Agent System. 10.3 Semantic Rules for Receiving Messages. 10.4 Semantics of the BDI Modalities for AgentSpeak. 11 Conclusions. 11.1 Jason and Agent-Oriented Programming. 11.2 Ongoing Work and Related Research. 11.3 General Advice on Programming Style and Practice. A Reference Guide. A.1 EBNF for the Agent Language. A.2 EBNF for the Multi-Agent Systems Language. A.3 Standard Internal Actions. A.4 Pre-Defined Annotations. A.5 Pre-Processing Directives. A.6 Interpreter Configuration. Bibliography.