Hello, I have started thinking about an extension of HaXml to better support XML Schema, i.e., to generate appropriate types (like DtdToHaskell) automatically (cf. Castor for Java). However, it is not obvious to me how to model mixed content (character data appears alongside subelements, i.e., it is not confined to the deepest subelement). Example (readers familiar with the problem may skip this): <salutation>Dear Mr.<name>Robert Smith</name>.</salutation> This structure is represented by the XML Schema <xsd:element name="salutation"> <xsd:complexType mixed="true"> <xsd:sequence> <xsd:element name="name" type="xsd:string"/> </xsd:sequence> </xsd:complexType> </xsd:element> How would you represent this in Haskell? A first idea may be to store the enclosing strings: data Salutation = Salutation String Name String This approach is not scaling well. E.g., there may be multiple names in the text... Do you have other ideas? Thank you and Happy Haskelling, Steffen
I have started thinking about an extension of HaXml to better support XML Schema, i.e., to generate appropriate types (like DtdToHaskell) automatically (cf. Castor for Java). However, it is not obvious to me how to model mixed content (character data appears alongside subelements, i.e., it is not confined to the deepest subelement).
We have worked on a XML Schema Haskell data binding, see Frank Atanassow, Dave Clarke, and Johan Jeuring. Scripting XML with Generic Haskell. In Proceedings of the 7th Brazilian Symposium on Programming Languages, SBLP 2003, 2003. and for just the data binding Frank Atanassow, Dave Clarke, and Johan Jeuring. UUXML: A Type-Preserving XML Schema Haskell Data Binding. Both are available from my homepage: http://www.cs.uu.nl/~johanj/publications/publications.html The modelling of ,ixed content is rather intricate, I'm afraid. -- Johan
Hello, thank you for the references. Looks promising. I will read it carefully. A nice solution I really like was found by Alastair Reid. He proposed to me (hope it is ok to cite this) the declaration: data Salutation = [Either Char Name] We think it will not scale well, too, however, it is elegant due to its simplicity. Bye and thx, Steffen
On Mar 10, 2004, at 8:56 AM, s_mazanek@gmx.de wrote:
Example (readers familiar with the problem may skip this): <salutation>Dear Mr.<name>Robert Smith</name>.</salutation>
This structure is represented by the XML Schema
<xsd:element name="salutation"> <xsd:complexType mixed="true"> <xsd:sequence> <xsd:element name="name" type="xsd:string"/> </xsd:sequence> </xsd:complexType> </xsd:element>
How would you represent this in Haskell? A first idea may be to store the enclosing strings:
data Salutation = Salutation String Name String
This approach is not scaling well. E.g., there may be multiple names in the text...
No, according to the content model, there must be exactly one occurrence of "name" in the content of "salutation": not zero, and not more than one. To allow zero or more you need to add minOccurs and/or maxOccurs attributes. This is one of the ways that mixed content in XML Schema differs from that in DTD's, and is treated in the references Johan posted. So, on the contrary, your first declaration: data Salutation = Salutation String Name String is a better translation of this schema (fragment), than your second attempt: data Salutation' = Salutation' [Either Char Name] Regards, Frank
participants (4)
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Frank Atanassow -
Johan Jeuring -
s_mazanek＠gmx.de -
Steffen Mazanek