Clemens Vasters: Enterprise Development & Alien Abductions

Clemens Vasters: Enterprise Development & Alien Abductions
Thoughts about Microsoft .NET, Enterprise Services, XML and other dull and boring things.

Updated: 7/30/2002; 8:47:49 AM.

Sunday, July 28, 2002

A call for peace.

Loose and tight coupling can happily coexist, if we have a way to define what we're talking about:

<?xml version="1.0" encoding="utf-8"?>
<xs:schema targetNamespace="http://schemas.newtelligence.com/projects/xyz/customer"
           elementFormDefault="qualified"
           xmlns="http://schemas.newtelligence.com/projects/xyz/person"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:rdf ="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <xs:complexType name="person"
                    rdf:resource="http://www.daml.org/2002/06/webont/owl-ex#Person">
        <xs:sequence>
            <xs:element name="shoesize"
                        type="xs:string"
                        rdf:resource="http://www.daml.org/2002/06/webont/owl-ex#shoesize"/>
                 <xs:annotation>
                        <xs:documentation>Mind the difference between physical and conceptual data types</xs:documentation>
                 </xs:annotation>
            </xs:element>
            <xs:element name="age"
                        type="xs:string"
                        rdf:resource="http://www.daml.org/2002/06/webont/owl-ex#age"/>
        </xs:sequence>
    </xs:complexType>
</xs:schema>

<?xml version="1.0" encoding="iso-8859-15" ?>
<IrgendwelchesXML xmlns="urn:ClemensEigenerNamensraum">
      <MeinKram>
             <Person rdf:resource="http://www.daml.org/2002/06/webont/owl-ex#Person">
                    <Schuhgröße rdf:resource="http://www.daml.org/2002/06/webont/owl-ex#shoesize">45</Schuhgröße>
             </Person>
     </MeinKram>
</IrgendwelchesXML>

<?xml version="1.0" encoding="iso-8859-15" ?>
<SomeArbitraryXML xmlns="urn:SamsOwnNamespace">
      <People >
             <Person name="Joe" rdf:resource="http://www.daml.org/2002/06/webont/owl-ex#Man" />
              <Person name="Jill" rdf:resource="http://www.daml.org/2002/06/webont/owl-ex#Woman"/>
      </People>
</SomeArbitraryXML>

If it isn't yet obvious what I mean, go here

9:18:42 PM      comment []

Sam Ruby: Looks like we are farther apart than I would have thought. I would have said that tight coupling is indeed a Good Thing for 1:1 and, in a bit more limited fashion, for 1:N communication environments; in N:M way environments, getting complete agreement on a set of tight rules is practically impossible.

Complete agreement may be a problem, but agreement on a composite, well-defined subset of things that both parties are interested in and understand is not. A party should also be able to disagree at some point and explicitly break an agreement.

(I guess it's soon time to start discussing the next topic: How "aspects" applied to schemas may be a way towards mutual happiness.)

4:52:16 PM      comment []

Dare Obasanjo looked at my Schema & Semantics bit and thinks that it doesn't make sense. I really wish I could agree with him and Sam Ruby and others on this whole issue, because the world would be a very nice place if loose coupling would always work. Loose coupling is indeed a Good Thing for 1:1 and, in a bit more limited fashion, for 1:N communication environments; in N:M way environments, the lack of tight rules is a call for chaos.

In an environment with network virtualization through SOAP extensibility, we will see N:X^Y:M environments, where routing infrastructures doing things as defined in WS-Routing will redirect Web Service invocations based on filtering rules and may do full or partial validation of content on the way for several, including security reasons and many other things in that fashion. In my world, a Web Service is not a singular thing that runs on a web farm - it's ubiquituous in a huge infrastructure that's driven by Schema and WSDL. It may have one endpoint or a million endpoints (like: "every Nokia cellphone" or "every Ford car"). Once you set a WSDL and it's base XSDs free into the wild, they become adopted and absorbed by things that you probably don't even know and likely can't see. So, while my rules may be bit strict for the now and here, the Internet as the XML post office will require a rules framework like that (Note: I don't say "This is it").

1:57:28 PM      comment []