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I am just ramping up on REST. Please forgive me if my
questions/comments are naive.
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Is REST Truly Scalable?
I have read that one advantage of REST is scalability: "REST works
because it keeps complexity from scaling with N^2" [1]
I am skeptical of this argument.
I agree that REST is highly scalable in the case of processing HTML (I
shall refer to this as HTML-REST). The reason that this is true is
twofold:
(1) A browser blindly displays the HTML on a screen, i.e., there is no
semantic processing of the data.
(2) A human does the semantic processing of what's displayed on the
screen.
In the case of machine processing of HTML then HTML-REST is on the
order of N^2, i.e., each machine must have n customized programs to
process the n HTML web sites.
Now consider the case where web sites serve up XML not HTML (I shall
refer to this as XML-REST). Suppose that the XML is programmatically
processed. The HTTP methods (GET, POST, PUT, etc) provide a nice set of
**access methods** for getting and putting the XML data. Thus,
**accessibility** is scalable as it is on the order of linear. However,
**processing** the XML data still needs customized code (just like
machine processing of HTML requires custom code). I therefore conclude
that XML-REST is no more scalable than SOAP.
In general REST is not scalable when processed by machines. The only
reason that it is scalable with HTML is because our brains are
infinitely adaptable, i.e., as we see a new HTML rendition our brain can
quickly parse it and understand it. Note: I do agree that SOAP is not
scalable. Thus, as I see it, both SOAP and REST miss the mark.
Am I missing something?
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Creating a Scalable, Machine-Processable Web Services Architecture
How can we make XML-REST scalable? One solution would be to require
every web site to serve up the same type of XML documents, i.e., have a
universal Schema that all XML documents conform to. Obviously this is
not a very attractive solution. The other solution is to have web sites
serve up documents whose meaning can be dynamically "discovered". I
believe that RDF is the only XML technology that enables dynamic
understanding of content. Thus, the cornerstone for a scalable,
machine-processable web services architecture is:
1. The HTTP access methods - GET, POST, PUT, etc
2. A dynamically understandable vocabulary, such as RDF.
Comments? /Roger
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[1] RESTwiki web site
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