[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Syntax and semantics
Assertion: Putting all the semantics of a message into a message is impossible. Here is why: I have a file here called foo.ps. It can be thought of as a stream of bytes. It can be thought of as a collection of tokens that can be summoned forth with the aid of a grammar. It can be though of as combination of executable code with embedded chunks of data. It can be interpreted in a multitude of different ways. In short, it has many semantic views depending on what a process is doing with the resource at a given point in time. The latter "view" of the foo.ps resource is more commonly expressed in English by the phrase "Postscript file". Now, If I send foo.ps to you over the Internet, does it contain semantics as well as syntax? Yes. It is clearly more than just data. It contains both data *and* the code to interpret that data in the form of a Postscript program. Is the semantic component of foo.ps self contained? No. In order for foo.ps to be "rendered" as is the life wish of Postscript files, a processor has to have a-priori capability to interpret and execute Postscript programs. No matter how you cut it, external semantics are a requirement to get anything done! Produce an utterly self contained message with no need for externally agreed semantics is impossible it seems to me. What is the most basic type of self contained message? Probably a stream of 1's and 0's to be interpreted as code to be executed by a Turing machine. Can a single message be constructed that contains both the semantics of a Turing machine and the data to feed to the Turing machine once constructed? It just ain't possible, right? regards, Sean, *************************************************************************** This is xml-dev, the mailing list for XML developers. To unsubscribe, mailto:majordomo@x...&BODY=unsubscribe%20xml-dev List archives are available at http://xml.org/archives/xml-dev/ ***************************************************************************
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