Question

What are the key factors to be considered with the most appropriate type of reuse?

Which features are supported by most of the web application frameworks?

What are some essential elements of component based software engineering?

Answer 1

Please find my answers:

First Answer: One should consider when planning reuse are:
1. The development schedule for the software: If the software has to be developed quickly, you should try to reuse off-the-shelf systems rather than individual components. These are large-grain reusable assets. Although the fit to requirements may be imperfect, this approach minimizes the amount of development required.

2. The expected software lifetime: If you are developing a long-lifetime system, you should focus on the maintainability of the system. You should not just think about the immediate benefits of reuse but also of the long-term implications. Over its lifetime, you will have to adapt the system to new requirements, which will mean making changes to parts of the system. If you do not have access to the source code, you may prefer to avoid off-the-shelf components and systems from external suppliers; suppliers may not be able to continue support for the reused software.

3. The background, skills, and experience of the development team: All reuse technologies are fairly complex and you need quite a lot of time to understand and use them effectively. Therefore, if the development team has skills in a particular area, this is probably where you should focus.

4. The criticality of the software and its non-functional requirements: For a critical system that has to be certified by an external regulator, you may have to create a dependability case for the system. This is difficult if you don’t have access to the source code of the software. If your software has stringent performance requirements, it may be impossible to use strategies such as generator-based reuse, where you generate the code from a reusable domain specific representation of a system. These systems often generate relatively inefficient code.

5. The application domain: In some application domains, such as manufacturing and medical information systems, there are several generic products that may be reused by configuring them to a local situation. If you are working in such a domain, you should always consider these as an option.
6. The platform on which the system will run: Some components models, such as .NET, are specific to Microsoft platforms. Similarly, generic application systems may be platform-specific and you may only be able to reuse these if your system is designed for the same platform.

Second Answer:

Mostly Web apps frameworks support the following features
1. Security WAFs may include classes to help implement user authentication (login) and access control to ensure that users can only access permitted functionality in the system.
2. Dynamic web pages Classes are provided to help you define web page templates and to populate these dynamically with specific data from the system database.
3. Database support Frameworks don’t usually include a database but rather assume that a separate database, such as MySQL, will be used. The framework may provide classes that provide an abstract interface to different databases.
4. Session management Classes to create and manage sessions (a number of interactions with the system by a user) are usually part of a WAF.
5. User interaction Most web frameworks now provide AJAX support, which allows more interactive web pages to be created.

Third Answer: Essentials elements of component bases sw engineering

• Independent components specified by their interfaces.
• Component standards to facilitate component integration.
• Middleware that provides support for component inter-operability.
• A development process that is geared to reuse.

but these are not limited to other characteristics like;

Composable
For a component to be composable, all external interactions must take place through publicly defined interfaces. In addition, it must provide external access to information about itself, such as its methods and attributes.
Deployable
To be deployable, a component has to be self-contained. It must be able to operate as a stand-alone entity on a component platform that provides an implementation of the component model. This usually means that the component is binary and does not have to be compiled before it is deployed. If a component is implemented as a service, it does not have to be deployed by a user of that component. Rather, it is deployed by the service provider.
Documented
Components have to be fully documented so that potential users can decide whether or not the components meet their needs. The syntax and, ideally, the semantics of all component interfaces should be specified.
Independent
A component should be independent--it should be possible to compose and deploy it without having to use other specific components. In situations where the component needs externally provided services, these should be explicitly set out in a "requires" interface specification.