DTD Example (XML Bible)

[Praveen Zala]

Hi,
Suppose I am writing a DTD to have between 4 and 6 TEAM elements for a DIVISION element, how do I go about specifying this ?
Please note - I cannot have three nor seven TEAM elements for the DIVISION in my Document, such a document must be forced to be treated as invalid.
Hint : I can try to enforce the same above by grouping TEAM elements in a sequence, but still, I have cracked this to atleast
have 4 elements but not the second criterion
Please get back with your suggestions.
Thanks and Regards,
Praveen Zala

[Ajith Kallambella]

AFAIK, DTD cannot support restricting the number of elements. The only thing you can do is specify very generic cardinality - zero or more, one or more or zero or one. Given your requirements, these are not going to be of any use.
You have two options -

[list] Validate the document while parsing. This is fairly easy to do.

Create more than one TEAM elements that captures your restriction. For instance

<TEAMOF_4>
    <MEMBER1/>
    <MEMBER2/>
    <MEMBER3/>
    <MEMBER4/>
</TEAMOF_4>
<TEAMOF_6>
    <MEMBER1/>
    <MEMBER2/>
    <MEMBER3/>
    <MEMBER4/>
    <MEMBER5/>
    <MEMBER6/>
</TEAMOF_6>

With these two definition, you can define a <DIVISION> as an element that contains either </TEAMOF_4> or </TEAMOF_6>.
I accept this is not a very clean design given and introduces redundancy especially for <MEMBERx> elements, but it works!
Let me know if you have a better idea!
Cheers!
------------------
Ajith Kallambella M.
Sun Certified Programmer for the Java�2 Platform.
IBM Certified Developer - XML and Related Technologies, V1.
[This message has been edited by Ajith Kallambella (edited September 27, 2001).]

[Angie Lathum]

Can you use a schema instead of a dtd?
If so you could use the minOccurs and maxOccurs attributes to specify exactly what you want. Something like this:
<element name="division">
<complexType>
<element name="team" type="string"
minOccurs="4" maxOccurs="6"/>
</complexType>
</element>

[Ajith Kallambella]

Angie - eventhough it might seem like a good solution, the minOccurs="4" maxOccurs="6" constraing would allow 5 member teams too! I guess that would be wrong as per the initial requirement of allowing only 4 member and 6 member teams.
Right?

[Angie Lathum]

I thought the requirement was to have "between 4 and 6", so I thought 5 was wanted as valid also.
Anyway, I also found another way to do it with a dtd (and if 5 isn't wanted you can just leave the middle line out

<!ELEMENT division (
(team, team, team, team) |
(team, team, team, team, team) |
(team, team, team, team, team, team)>

Its not very elegant, but I guess it would work.
Angie

[Mapraputa Is]

Yeah... And you may want to read this: http://www.xml.com/pub/a/2001/09/26/q-and-a.html

[Praveen Zala]

Thank you all for your responses.
I had posted this on the XML Developer's Forum and look at some of the responses I got :
a) <!ELEMENT DIVISION (TEAM,TEAM,TEAM,TEAM,(TEAM,TEAM?)?) >
b) Use a Schema instead of a DTD.
<xsd:element name="team"
minoccurs="4"
maxoccurs="6"
type="xsd:string" />

Thanks and Regards,
Praveen Zala