Buzz roundtable: XML, 09/27/99

Error 404--Not Found

From RFC 2068 Hypertext Transfer Protocol -- HTTP/1.1:

10.4.5 404 Not Found

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent.

If the server does not wish to make this information available to the client, the status code 403 (Forbidden) can be used instead. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address.

Error 404--Not Found

From RFC 2068 Hypertext Transfer Protocol -- HTTP/1.1:

10.4.5 404 Not Found

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent.

XML

Network World Fusion, 09/27/99

XML is being incorporated into everything from Web browsers to network management applications to directories. It is being called the lingua franca that will enable data to be easily read and understood by various computer systems and applications. How important do you expect XML will be to enterprise users – and when?

Bradner: XML will be an interesting exercise in frustration. That fact that you can write in the same language doesn't mean you're writing the same thing in the same format, or with the same meaning. Unless there's much more agreement on the meaning of the terms and the format and the conceptual background, it's mostly going to be frustrating.

Kobielus: One of the things we're finding is a need to educate the industry as to what XML is and what it isn't. It isn't a lot of things. It isn't a protocol or a set of APIs. Rather, it's simply a very adaptable, handy markup syntax for defining documents, objects and formats by which the network can expose the structure and functionality of various resources.

XML is in many ways a great success in terms of being adapted for many different application domains. But XML, like Java, will not absorb the sum total of all standards that are out there. It's just yet another set of standards that are very handy and are filling a particular niche.

Nolle: XML offers something that Java has not offered and none of the other strategies that we've talked about have offered and that is, because XML does provide a mechanism for defining more than just Web pages – you can define objects and databases – XML lets us define behaviors of systems. Not in the same sense as a procedural language like Java, but in a sense that allows cooperative processes to share information with one another. And an awful lot of what we're talking about in new generation network services, both in the voice space and the data space, really comes about as a result of a relationship among cooperative processes inside the network. A call-forwarding function, for example, is a cooperative process. We can use XML to define not only how call-forwarding works for both the originating or forwarding switch and the final destination switch, we can also use XML to define the syntax or message that's used to exchange calls between the devices. Because XML is extensible, it could relieve us of some of the burdens that SS7 [Signaling System 7] and some of the other protocols have placed on us. Protocols are usually used to arbitrate information between cooperative systems but since they're not readily extensible, protocols often become the big brake on this.

Realistically, XML is more likely to affect users in the way that ATM has, which is to say behind the scenes, rather than something that the user will himself adopt. I wouldn't be terribly surprised if the average user, three or four years from now, was still not doing anything with his own Web development in XML. But I would be very surprised if within the next three years or so users weren't consuming XML indirectly, in the form of services or functions that are arbitrated through XML.

Kobielus: Right. XML is enabling a more loosely coupled application architecture. It's really doing an end-run on the likes of DCOM and CORBA. In other words, any two systems that can exchange XML objects can conceivably interoperate whether or not they're under the same operating system, or even whether they use the same object protocols. As long as they can generate, receive, process and parse an XML document, and understand the basic semantics that are encoded therein, you have the means for loose couplings of different systems. So voice and data systems can work together without being, for example, both Windows NT-based systems or being both Java or CORBA-based applications.

Bradner: All of you are pointing out the very important strength and the very important weakness of XML. It is not a defined thing. It is an extensibility platform. That means the likelihood of getting incompatible understandings of how to describe a call forwarding sequence, for example, is extremely high. The probability of that is close to 100% in XML and it's going to take a long time to work out the subsets for individual applications that make sense.

Nolle: I agree with that. Look at HTML, which is the only version of a markup language that people understand broadly. HTML has not only a predefined syntax, a non-extensible syntax, but it also has sort of a virtual machine associated with it. What you'd need to have XML drive the behavior of a cooperative system is define a virtual machine that represented the elements of that cooperative system. Otherwise your XML namespace is going to name variables which everyone agrees on but which no one can manipulate because they don't mean anything; there's no context to provide the meaning.

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