SE_Module-4_c) Application architectures.pptx
- 1. c) Application architectures • Data-processing systems • Transaction-processing systems • Event-processing systems • Language-processing systems
- 2. Data-processing systems • Businesses use data-processing systems to handle tasks like payroll, invoicing, accounting, and insurance renewals. • These systems process large amounts of data, often much larger than the systems themselves. • They typically operate as batch-processing systems, inputting and outputting data in batches from files or databases rather than interacting with users in real-time. • The systems analyze input records, perform actions based on specified criteria, update databases with results, and format data for output, such as printing.
- 3. • The architecture of batch-processing systems consists of three main components: 1.Input Component: Collects data from one or more sources. 2.Processing Component: Performs computations on the collected inputs. 3.Output Component: Produces outputs, such as updating databases or generating printouts. • For example, in a telephone billing system, customer records and meter readings (inputs) are processed to calculate costs, and the resulting bills (outputs) are printed for customers.as shown in fig below
- 5. • Data-flow diagrams are a way of representing function-oriented systems where each round-edged rectangle in the data flow represents a function that implements some data transformation, and each arrow represents a data item that is processed by the function. • Files or data stores are represented as rectangles. • The advantage of data-flow diagrams is that they show end-to-end processing
- 6. • The figure shows the design of a salary payment system. • In this system, information about employees in the organisation is read into the system, • monthly salary and deductions are computed, • and payments are made. • You can see how this system follows the basic input-process output structure:
- 8. 1. The functions on the left of the diagram Read employee record, Read monthly pay data and Validate employee data input the data for each employee and check that data. 3. The Compute salary function works out the total gross salary for each employee and the various deductions that are made from that salary. The net monthly salary is then computed. 4. The output functions write a series of files that hold details of the deductions made and the salary to be paid. These files are processed by other programs once details for all employees have been computed. A payslip for the employee, recording the net pay and the deductions made, is printed by the system.
- 9. Transaction-processing systems • Transaction-processing systems are designed to process user requests for information from a database or requests to update the database • a database transaction is sequence of operations that is treated as a single unit • All of the operations in a transaction have to be completed before the database changes are made permanent • This means that failure of operations within the transaction do not lead to inconsistencies in the database.
- 10. • An example of a transaction is a customer request to withdraw money from a bank account using an ATM.
- 11. • Figure 13.3 illustrates the high-level architectural structure of these applications. • First a user makes a request to the system through an I/O processing component. • The request is processed by some application-specific logic. A transaction is created and passed to a transaction manager, which is usually embedded in the database management system. • After the transaction manager has ensured that the transaction is properly completed, it signals to the application that processing has finished.
- 12. • This involves getting details of the customer’s account, checking the balance, modifying the balance by the amount withdrawn and sending commands to the ATM to deliver the cash. • Until all of these steps have been completed, the transaction is incomplete and the customer accounts database is not changed. • Figure 13.4 shows The software architecture of an ATM
- 14. • Figure 13.5 below shows another view of the architecture of a customer accounting system that handles personal account transactions from ATMs and counter terminals in a bank. • The teleprocessing monitor handles the input and serialises transactions, which it converts to database queries. • The query processing takes place in the database management system. • Results are passed back to the teleprocessing monitor, which keeps track of terminals making the request. • This system then organises the data into a form that can be handled by the terminal software and returns the results of the transaction to it.
- 16. • Figure 13.6 is a very general model of an information system. • where the top layer supports the user interface and the bottom layer the system database. • The user communications layer handles all input and output from the user interface. • and the information retrieval layer includes application-specific logic for accessing and updating the database.
- 18. ❖ Event-processing systems • Event-processing systems respond to events in the system’s environment or user interface. • the key characteristic of event-processing systems is that the timing of events is unpredictable and the system must be able to cope with these events when they occur. • We all use such event-based systems like this on our own computers— word processors, presentation systems and games are all driven by events from the user interface.
- 19. • The system processes screen events as commands, updates an internal data structure, and redisplays the updated content on the screen. • Objects in the system operate concurrently and autonomously, ensuring responsive interaction. • Real-time systems, by contrast, respond to external events (e.g., sensors), but editing systems focus primarily on user actions for document manipulation. • The responsibilities of the architectural components shown in Figure 13.10 are:
- 21. 1. Screen This object monitors the screen memory segment and detects events that occur. These events are then passed to the event- processing object along with their screen coordinates. 2. Event This object is triggered by an event arriving from Screen. It uses knowledge of what is displayed to interpret this event and to translate this into the appropriate editing command. This command is then passed to the object responsible for command interpretation. For very common events, such as mouse clicks or key presses, the event object can communicate directly with the data structure. This allows faster updates of that structure.
- 22. 3. Command This object processes a command from the event object and calls the appropriate method in the Editor data object to execute the command. 4. Editor data When the appropriate command method in Editor data object is called, it updates the data structure and calls the Update method in Display , to display the modified data.
- 23. 5. Ancillary data : It acts as as the data structure itself, editors manage other data such as styles and preferences .Some editor commands, such as a command to initiate a spelling check, are implemented by a method in this object. 6. File system This object handles all opening and saving of files. These can be either editor data or ancillary data files. To avoid data loss, many editors have auto-save facilities that save the data structure automatically. This can then be retrieved in the event of system failure. 7. Display This object keeps track of the organisation of the screen display. It calls the Refresh method in Screen when the display has been changed.
- 24. ❖ Language-processing systems • Language-processing systems take natural or artificial language as input and produce another representation as output. • Language-processing systems are used to translate texts from one language into another and to carry out the instructions specified in the input language. They include a translator and an abstract machine that executes the generated language. • Examples include compilers that translate high-level code into machine code, systems that process XML into database queries, and natural language processors for language translation.
- 25. • Lage-processing systems are used when solutions are best specified as algorithms or data descriptions, such as meta-CASE tools that generate CASE tools for software engineering methods. • CASE tools use a special-purpose language to describe method, components and rules, which is analyzed to configure the generated tool. • the architecture of a language-processing system is illustrated in Figure 13.11.
- 27. • The instructions describe what has to be done and are translated into some internal format by a translator. • These instructions are then interpreted by another component that fetches the instructions for execution and executes them using, data from the environment. • The output of the process is the result of interpreting the instructions on the input data. • For many compilers, the interpreter is a hardware unit that processes machine instructions and the abstract machine is a real processor. • However, for languages such as Java, the interpreter is a software component.
- 28. Translators in a language-processing system have a generic architecture (Figure 13.12) that includes the following components:
- 29. Translators in a language-processing system have a generic architecture (Figure 13.12) that includes the following components: 1. A lexical analyser, which takes input language tokens and converts them to an internal form 2. A symbol table, which holds information about the names of entities (variables, class names, object names, etc.) used in the text that is being translated
- 30. 3. A syntax analyser, which checks the syntax of the language being translated. It uses a defined grammar of the language and builds a syntax tree 4. A syntax tree, which is an internal structure representing the program being compiled 5. A semantic analyser, which uses information from the syntax tree and the symbol table to check the semantic correctness of the input language text 6. A code generator, which ‘walks’ the syntax tree and generates abstract machine code
- 31. The generic system components can then be organised in a repository based model, as shown in Figure • This figure illustrates how a language- processing system can be part of an integrated set of programming support tools. • the symbol table and syntax tree act as a central information repository. Tools or tool fragments communicate through it. • Other information that is sometimes embedded in tools, such as the grammar definition and the definition of the output format for the program, have been taken out of the tools and put into the repository. • Therefore, a syntax-directed editor can check that the syntax of a program is correct as it is being typed, • and a pretty printer can create listings of the program in a format that is easy to read.
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