External Data Representation XDR
1 External Data Representation (XDR)
Introduction o Examines a de facto standard for external data representation and presentation as well as a set of library procedures used to perform data conversion o Describes the general motivations for using an external data representation and the details of one particular implementation
2 Introduction Examines a de facto standard for external data representation and presentation as well as a set of library procedures used to perform data conversion Describes the general motivations for using an external data representation and the details of one particular implementation
Introduction(cont) o The next chapter shows how an external data representation standard helps simplify client and server communication o It illustrates how a standard makes it possible to use a single, uniform remote access mechanism for client-server communication
3 Introduction (cont.) The next chapter shows how an external data representation standard helps simplify client and server communication It illustrates how a standard makes it possible to use a single, uniform remote access mechanism for client-server communication
Representation of Data o Fig. 20. 1 shows little endian(if it stores the lsb of an integer at the lowest memory address) and big endian representation for 32-bit integers o Programmers who create client and server software must contend with data representation because both endpoints must agree on the exact representation for all data sent across the communication channel between them otherwise conversion is required
4 Representation of Data Fig. 20.1 shows little endian (if it stores the LSB of an integer at the lowest memory address) and big endian representation for 32-bit integers Programmers who create client and server software must contend with data representation because both endpoints must agree on the exact representation for all data sent across the communication channel between them; otherwise, conversion is required
Asynchronous conversion and the n-squared problem o Designs that follow the paradigm of converting directly from one representation to the server s representation are said to use asymmetric data conversion because only one side needs to perform conversion
6 Asynchronous Conversion and the N-Squared Problem Designs that follow the paradigm of converting directly from one representation to the server’s representation are said to use asymmetric data conversion because only one side needs to perform conversion