3.7 Limitations

Each architectural style promotes a certain type of interaction among components. When components are distributed across a wide-area network, use or misuse of the network drives application usability. By characterizing styles by their influence on architectural properties, and particularly on the network-based application performance of a distributed hypermedia system, we gain the ability to better choose a software design that is appropriate for the application. There are, however, a couple limitations with the chosen classification.

The first limitation is that the evaluation is specific to the needs of distributed hypermedia. For example, many of the good qualities of the pipe-and-filter style disappear if the communication is fine-grained control messages, and are not applicable at all if the communication requires user interactivity. Likewise, layered caching only adds to latency, without any benefit, if none of the responses to client requests are cacheable. This type of distinction does not appear in the classification, and is only addressed informally in the discussion of each style. I believe this limitation can be overcome by creating separate classification tables for each type of communication problem. Example problem areas would include, among others, large grain data retrieval, remote information monitoring, search, remote control systems, and distributed processing.

A second limitation is with the grouping of architectural properties. In some cases, it is better to identify the specific aspects of, for example, understandability and verifiability induced by an architectural style, rather than lumping them together under the rubric of simplicity. This is particularly the case for styles which might improve verifiability at the expense of understandability. However, the more abstract notion of a property also has value as a single metric, since we do not want to make the classification so specific that no two styles impact the same category. One solution would be a classification that presented both the specific properties and a summary property.