tailieunhanh - Building Secure and Reliable Network Applications phần 3

Với sự xuất hiện của ngôn ngữ lập trình hướng đối tượng, chẳng hạn như Modula và C + +, đến một sự công nhận rằng định hướng đối tượng có thể đóng một vai trò tương tự như của hệ thống phân cấp OSI, nhưng đối với hệ thống phân phối phức tạp. | 104 Kenneth P. Birman - Building Secure and Reliable Network Applications 6. CORBAand Object-Oriented Environments With the emergence of object-oriented programming languages such as Modula and C came a recognition that object-orientation could play a role similar to that of the OSI hierarchy but for complex distributed systems. In this view one would describe a computing system in terms of the set of objects from which it was assembled together with the rules by which these objects interact with one another. Object oriented system design became a major subject for research with many of the key ideas pulled together for the first time by a British research effort called the Advanced Network Systems Architecture group or ANSA. In this chapter we will briefly discuss ANSA and then focus on a more recent standard called CORBA which draws on some of the ideas introduced by ANSA and has emerged as a widely accepted standard for objected oriented distributed computing. TheANSAProject The ANSA project headed by Andrew Herbert was the first systematic attempt to develop technology for modelling complex distributed systems ANSA89 ANSA91a ANSA91b . ANSA stands for the Advanced Network Systems Architecture and was intended as a technology base for writing down the structure of a complex application or system and then translating the resulting description into a working version of that system in a process of stepwise refinement. Abstractly ANSA consists of a set of models that deal with various aspects of distributed systems design and representation problem. The enterprise model is concerned with the overall functions and roles of the organizational structure within which the problem at hand is to be solved. For example an air-traffic control system would be an application within the air-traffic control organization an enterprise . The information model represents the flow of information within the enterprise in an air-traffic application this model might describe .