Summary of Context Awareness

For the comparison of the presented context awareness concepts three criteria are used:

1.

level of integration of profiles into implementation classes

2.

programming and maintenance effort when the number of implementation classes increases

3.

flexibility in describing environments

The integration classifies how close the implementation profile is tied to the implementation class in terms of coding: e.g. same language, same file. The rule based approach has no relation between the implementation profile and the implementation class. The names of the implementation classes are listed in a different file, even in a different programming language. If e.g. the name of the implementation class changes from Configuration_UX_NETSCAPE to Configuration_WINNT_IEXPLORER there is no guarantee that the rule file is compulsory updated. The info components are implemented in the same language as the implementation class and they are associated through the common root of their class name. A higher level of integration is achieved by the last proposal, where the implementation profiles are coded in the implementation class itself.

The scalability addresses the applicability of the concept when the number of implementation classes increases. For a higher number of classes the rule based approach still offers an acceptable solution, perhaps supported by an editor with syntax high-lightning or a graphical editor. The info component model has an unacceptable level of scalability. The number of classes doubles and results in higher programming effort, but also in a more complex maintenance. The integrated profiles are not influenced by the number of implementation classes because no further classes or files are needed apart from the implementation classes which are necessary anyway.

The flexibility addresses the way to describe environments. The more flexible the description mechanism is, the more environments and more precisely can be specified. The rule base context awareness relies strongly on the power of the language and is therefore ranked on a middle level of flexibility. High flexibility have both the info components and the integrated profiles. They can both use Java language constructs for the association of profile values and define own matching functions.

 

Figure: Cirteria for the evaluation of context awareness concepts  

Figure shows a graphical summary of the evaluation of the various context awareness concepts. There are three levels for every category: e.g. no scalability, acceptable scalability, good scalability. From this evaluation the conclusion can be drawn that integrated profiles represent the most suitable approach for context awareness and will be used for the implementation of the prototype.

A very subtle point of this concept is the design of the repository, which is responsible for loading implementation classes and delevering the implementation profiles to the adaptation mechanism.