Sof_Main_Evol_5_p1

In Oxford English Dictionary (OED) the word “legacy” is defined as A sum of money, or a specified article, given to another by will; anything handed down by an ancestor or predecessor. Others used the following definition to define legacy systems: any information system that significantly resists ___________________ to meet new and constantly changing business requirements. Bennett used the following definition to define legacy systems: Legacy software systems are large software systems that we don’t know how to cope with but that are ________________ . عارف. مش عارف.

Supporting the definitions are a set of acceptable features of a ____ system: • large with millions of lines of code. • geriatric, often more than 10 years old. • written in obsolete programming languages. • lack of ____________________. • poor management of data, often based on ______________. • degraded structure following years of modifications. • very difficult, if not impossible, to expand. • runs on _____ ______. عارف. مش عارف.

___________ means encapsulating the legacy component with a new software layer that provides a new interface and hides the complexity of the old component. The encapsulation layer can communicate with the ___________ through sockets, remote procedure calls (RPCs), or predefined application program interfaces (API). The wrapped component is viewed similar to a _________; it provides some service required by a client that does not know the _________________ of the server. عارف. مش عارف.

Wrapping By means of a ________________ mechanism, a wrapper connects to the clients. On the input front, the wrapper accepts _________, restructures them, and invokes the target object with the ________ arguments. On the output front, the wrapper captures outputs from the ______ entity, restructures the outputs, and pushes them to the ____________. However, this technique does not solve the problems with ___________ . عارف. مش عارف.

Types of Wrapping It classified wrappers into four categories: _________ wrappers. ________ wrappers. ________ wrappers. _______ wrappers. عارف. مش عارف.

Database wrappers: Database wrappers can be further classified into forward wrappers (f-wrappers) and backward wrappers (b-wrappers) The forward wrappers-approach shows the process of _____________________________. Therefore, by means of _________ service involving both ______ data and queries, the wrapper integrates the new component with the legacy system. The backward wrappers-approach. In this approach, data are ____________ then new components are _______ that use the new database; the ____________ access the new data via wrappers. عارف. مش عارف.

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________________ wrappers: This kind of wrappers support customized access to commonly used system services, namely, routing, sorting, and printing. A __________ may access those services without knowing their interfaces. عارف. مش عارف.

___________ wrappers: This kind of wrappers encapsulate online transactions or __________ . These _________ enable new clients to include legacy components as _______ and invoke those objects to produce reports or update files. عارف. مش عارف.

_____________ wrappers: This kind of wrappers provide an interface to call functions in a __________ . In this mechanism, only _________________ – and not the ___ program – are invoked from the client applications. Therefore, _______ access is provided by function wrappers. عارف. مش عارف.

Levels of Encapsulation Sneed classified five levels of granularity: ________ are at the lowest level and processes are at the _______. Process level ________ ________ ________ Procedure level: عارف. مش عارف.

__________ level: A job is started on the server which accepts input data, accesses databases, and produces ______. The input data and output data are contained in ______. The input files are created by the _________ and are transferred to the server by the _____ by means of a standard file transfer utility. Upon the completion of the job, the wrapper takes over the output files to be forwarded to the client. عارف. مش عارف.

_________ level: On the server, a virtual terminal is created that sends the terminal ____ map and receives the terminal ____ map. The wrapper is a program which simulates ___________. This type transaction level wrapping has become simple because modern transaction processors: (i) take care of ______________________. (ii) perform _____ and __________, exception handling, rollback, and commit. عارف. مش عارف.

_________ level: Via APIs, batch programs are called in a ________. The wrapper substitutes program inputs with data inputs coming in from the ____________. In addition, outputs from the wrapped program are captured, reformatted, and ___________. عارف. مش عارف.

________ level: Legacy modules are executed using their standard interfaces. A significant deviation from the usual calls is that parameters are passed by ______ – and not by _________. Therefore, first, the wrapper buffers the received values in its own ______________. Next, the buffered values are passed on to the ___________. Finally, the output values received from the invoked module are passed on to the ______. عارف. مش عارف.

__________ level: A procedure internal to the system is invoked as if the procedure was compiled ________. As a result, this special treatment of an internal procedure requires: (i) constructing a _________; and (ii) if needed, _________________ before calling the procedure. عارف. مش عارف.