Hi Huichan:

thank you for pushing for correct test cases for Prasenjit's
generator. I am amazed how complicated XML schema is. If it would be well
designed, it should be easy to express expressions
elegantly.

Your analysis seems right that extension
is not the right way to
express alternation. Extension seems to allow to
extend a type but it does not give us alternation.

In 
http://www.w3.org/TR/2000/CR-xmlschema-2-20001024/
I read:

[Definition:]  Union datatypes are those whose value spaces and lexical spaces are the union of the value spaces and lexical spaces of two or more other datatypes. 

This sounds more like alternation. I look forward to
your schema that defines E as a union of S and C.

This is high priority work because without solid examples,
Prasenjit cannot write the generator.

-- Karl

From hche@coe.neu.edu  Wed Feb 28 12:46:30 2001
Date: Wed, 28 Feb 2001 12:44:15 -0500 (EST)
From: Huichan He <hche@coe.neu.edu>
To: Karl Lieberherr <lieber@ccs.neu.edu>
cc: adakp@ccs.neu.edu, jing@ccs.neu.edu, zhzhu@MIT.EDU
Subject: Re: XML doc checking and MI

Hi professor,

The schema I wrote yesterday was actually according to this CD:
Exp = C.
C = <op> Op <arg> List(S).
S = [Exp] [<value> int].
Op = string.

So, C can contain Op, value, or other C.

I wrote another xml schema according to the CD you gave me. I found that
the alternation in CD can not be directly translated to extension
relationship in schema. For example,
E : S | C.
can not be expressed as:
<complexType name="S">
<complexContent>
<extension base="E">
...

<complexType name="C">
<complexContent>
<extension base="E">
... 
The reason is, in CD the part of S and C are also part of E, whileas in
schema, the child element of S and C can not be taken as the child of E.
This is confirmed by XML spy.

So, I think a solution could be switching the roles in the extension
relationship:
<complexType name="E">
<complexContent>
<extension base="C">
... 
and at the same time, let E contain a child element of type S. This way
will guarantee that the child of S and C will also be child of E.

The schema for the cd you gave me is attached below:

<xsd:schema xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">

<xsd:element name="container" type="Exp"/>
<xsd:complexType name="Exp">
 <xsd:sequence>
  <xsd:element name="expression" type="E"/>
 </xsd:sequence>
</xsd:complexType>
	
<xsd:complexType name="E">
 <xsd:complexContent>
  <xsd:extension base="C">
   <xsd:sequence>
    <xsd:element name="s_value" type="S" minOccurs="0"/>
   </xsd:sequence>
  </xsd:extension>
 </xsd:complexContent>
</xsd:complexType>
	
<xsd:complexType name="S" >
 <xsd:sequence>
  <xsd:element name="value" type="xsd:int"/>
 </xsd:sequence>
</xsd:complexType>
	
<xsd:complexType name="C">
 <xsd:sequence>
  <xsd:element name="op" type="xsd:string" minOccurs="0"/>
  <xsd:element name="arg" type="Exp" minOccurs="0"
   maxOccurs="unbounded"/>
 </xsd:sequence>
</xsd:complexType>

</xsd:schema>

This schema allows the XML doc you sent me before about (+ 3 5).

I think we might also do this with union type in xml schema. I'll let you
know the detail after i figure it out.

Huichan
---------------------------
Huichan He
Teaching Assistant
334 Snell Engineering Center
Northeastern Univ

Email: hche@coe.neu.edu
Tel: (617)373-5340

On -1 xxx -1, Huichan He wrote:

> Hi professor,
> 
> I expressed (+ 3 (* 6 7 8 )) by the following schema and document. I
> didn't use abstract type here, cause I don't think it's necessary for this
> problem. They were validated by XML spy.
> 
> -------------XML Schema------------------------
> -----------------------------------------------
> 
> <xsd:schema xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">
> <xsd:element name="container" type="Exp"/>
> 	
> <xsd:complexType name="Exp">
>  <xsd:sequence>
>   <xsd:element name="expression" type="C"
>    minOccurs="0"/>
>  </xsd:sequence>
> </xsd:complexType>
> 		
> <xsd:complexType name="S">
>  <xsd:complexContent>  
>   <xsd:extension base="Exp">
>    <xsd:sequence>
>     <xsd:element name="value" type="xsd:int"
>      minOccurs="0" />
>    </xsd:sequence>
>   </xsd:extension>
>  </xsd:complexContent>
> </xsd:complexType>
> 
> <xsd:complexType name="C">
>  <xsd:sequence>
>   <xsd:element name="op" type="xsd:string"/>
>   <xsd:element name="arg" type="S"
>    minOccurs="0" maxOccurs="unbounded"/>
>  </xsd:sequence>
> </xsd:complexType>
> 
> </xsd:schema>
> 
> 
> -----------------XML Document-------------
> ------------------------------------------
> <?xml version="1.0" encoding="UTF-8"?>
> <container xmlns:xsi="http://www.w3.org/2000/10/XMLSchema-instance"
> xsi:noNamespaceSchemaLocation="D:\huichan\thesis-soft\schema test
> cases\pras-3.xsd">
> <expression>
>   <op>"+"</op>
>   <arg>
>     <expression>
>       <op>"*"</op>
>       <arg>
>         <value>6</value>
>       </arg>
>       <arg>
>         <value>7</value>
>       </arg>
>       <arg>
>         <value>8</value>
>       </arg>
>     </expression>
>   </arg>
>   <arg>
>     <value>3</value>
>   </arg>
> </expression>
> </container>
> 
> 
> Huichan He
> Teaching Assistant
> 334 Snell Engineering Center
> Northeastern Univ
> 
> Email: hche@coe.neu.edu
> Tel: (617)373-5340
> 
> 
>