Hello, >From HTTP Server Middleware Meta Document:
The design pattern used by middleware has existed for many years as the pipeline > pattern <https://en.wikipedia.org/wiki/Pipeline_(computing)>, or more > specifically, "linear pipeline processing". > I'm trying to understand how does the pipeline pattern fits into proposed concept of middleware and I'm failing to see the connection. The link to Wikipedia <https://en.wikipedia.org/wiki/Pipeline_(computing)> states: In computing, a pipeline is a set of data processing elements connected in > series, where the output of one element is the input of the next one. > But this is not what proposed middlewares are doing. If one middleware takes an request as input and output an response then the response can not be inputted into a next middleware, because of the type mismatch. Am I right? The concept of *linear pipeline processing* is even more fuzzy to me. According to the Wikipedia: A linear pipeline processor is a series of processing stages and memory > access. To me it seems to be completely out of context of the proposed middleware standard recommendation and doesn't provide any reference to the source literature. Another page in the Wikipedia about pipelines in software engineering <https://en.wikipedia.org/wiki/Pipeline_(software)> seems to be more illuminating: Narrowly speaking, a pipeline is linear and one-directional, though > sometimes the term is applied to more general flows. For example, a > primarily one-directional pipeline may have some communication in the other > direction, known as a *return channel* or *backchannel,* as in the lexer > hack, or a pipeline may be fully bi-directional. Flows with > one-directional tree and directed acyclic graph topologies behave > similarly to (linear) pipelines – the lack of cycles makes them simple – > and thus may be loosely referred to as "pipelines". > Although I still fail to see how middlewares can be arranged in pipeline (input - output type conflict I mentioned) and why they are linear. To sum up - the statement at the beginning of the HTTP Server Middleware Meta Document is in my opinion more confusing than illuminating. I propose to remove it or elaborate on it more, preferably with links to the source literature or at least to the second Wikipedia page that I mentioned. Thank you for your comments in advance :) ! -- You received this message because you are subscribed to the Google Groups "PHP Framework Interoperability Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to php-fig+unsubscr...@googlegroups.com. To post to this group, send email to php-fig@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/php-fig/688b75ce-5800-4941-94e7-9f8f8dcb613d%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
