RE: [xml-dev] generate common xml shema from multiple xml instances

["Paul Spencer" <xml-dev-list@boynings.co.uk>]

XML to schema tools tend to allow the user to set various options. For example, XML Spy asks if you want to create enumerations or not. If you had a single instance, you might just get

<xs:simpleType name="Color">
  <xs:restriction base="xs:string">
    <xs:enumeration value="RED" />
  </xs:restriction>
</xs:simpleType>

As Mukul says, it is then up to the schema author to fix this. I saw the original message as trying to improve this "first cut" by taking account of several instance documents. The complexity of the tool goes up markedly with more than one instance. For example, how would you handle this:

Instance 1
<a>
  <b/>
  <c/>
</a>

Instance 2
<a>
  <b/>
  <d/>
</a>

Is there a choice between c and d? Or are both optional? If optional, which order do they go in?

Since the schema can only be a first cut, it is unlikely that the additional complexity of handling multiple instances is worthwhile, nice though the idea is. It looks like the tool developers agree.

Paul


> -----Original Message-----
> From: Mukul Gandhi [mailto:gandhi.mukul@gmail.com]
> Sent: Thursday, June 18, 2009 8:52 AM
> To: Rita Shen
> Cc: xml-dev@lists.xml.org
> Subject: Re: [xml-dev] generate common xml shema from multiple xml
> instances
> 
> I further see following issues with the usefulness of XML to XSD
> conversion tools.
> 
> 1) Suppose a following element exists in the XML document.
> 
> <color>RED</color>
> 
> How would the "XML to Schema" conversion tool guess, that the element
> "color" represents a "visual attribute of things" and generate a
> simple type declaration like below:
> 
> <xs:simpleType name="Color">
>   <xs:restriction base="xs:string">
>     <xs:enumeration value="RED" />
>     <xs:enumeration value="GREEN" />
>     <xs:enumeration value="YELLOW" />
>   </xs:restriction>
> </xs:simpleType>
> 
> Which the Schema author may want to do.
> 
> In the abscence of this semantic intelligence, the Schema generation
> tool may generate a Schema declaration like following:
> 
> <xs:element name="color" type="xs:string" />
> 
> 2) It may be difficult for the tool to reuse type definitions. In case
> of structural similarities in a large XML document, or a set of XML
> documents, the tool may generate lot of Schema types, which the Schema
> author may like to refactor.
> 
> Though I believe, the XML to Schema conversion tools may be useful to
> quickly generate a Schema, which could be further enahanced and
> refactored by the Schema author.
> 
> On Wed, Jun 17, 2009 at 11:33 AM, Mukul Gandhi<gandhi.mukul@gmail.com>
> wrote:
> > Hi,
> > � If you are looking to build such a utility yourself, you need to
> > consider few points, like mentioned below:
> >
> > Let's say your instance document is following (i.e., having two
> > "person" elements):
> >
> > <people>
> > �<person>..</person>
> > �<person>..</person>
> > </people>
> >
> > You need to decide for example:
> >
> > 1) What value of occurrence indicator, you want to have? Do you need
> > the value "unbounded" or want it to be a specific number?
> >
> > for e.g.,
> >
> > <xs:element name="person" type="Person" maxOccurs="unbounded" />
> >
> > OR
> >
> > <xs:element name="person" type="Person" maxOccurs="10" />
> >
> > 2) Should the complex type "Person" be a named type or an anonymous
> type?
> >
> > Inferring the XSD structure in an automated way from multiple XML
> > files, could be inaccurate.
> >
> > I believe, you need some amount of manual adjustment of the XSD, even
> > if it's generated by some tool.
> >
> > On Wed, Jun 17, 2009 at 10:54 AM, Rita Shen<shaledova@gmail.com>
> wrote:
> >> Hi,
> >>
> >> How can I generate a common XML schema for multiple xml instances??
> >> I know many tools can generate an XSD from a single XML instance.
> >> But in my case, I want to get the unknown common XSD for a bunch of
> XML
> >> instances.
> >>
> >> Thanks for any help,
> >> syt
> 
> 
> 
> --
> Regards,
> Mukul Gandhi
> 
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