Typing an XSLT template/function as a sequence constructor?

Question

Very simply, is it possible to type an XSLT template or function to return a named sequence constructor?

e.g. in FpML, there is the Product.model group, which simply contains two elements (ProductType and ProductId). I'd like to be able to create a typed template which returns that sequence, but have no idea what the "as" attribute should contain.

Update

I'll include the relevant bit of the FpML schema for convenience :

<xsd:group name="Product.model">
<xsd:sequence>
  <xsd:element name="productType" type="ProductType" minOccurs="0" maxOccurs="unbounded">
    <xsd:annotation>
      <xsd:documentation xml:lang="en">A classification of the type of product. FpML defines a simple product categorization using a coding scheme.</xsd:documentation>
    </xsd:annotation>
  </xsd:element>
  <xsd:element name="productId" type="ProductId" minOccurs="0" maxOccurs="unbounded">
    <xsd:annotation>
      <xsd:documentation xml:lang="en">A product reference identifier allocated by a party. FpML does not define the domain values associated with this element. Note that the domain values for this element are not strictly an enumerated list.</xsd:documentation>
    </xsd:annotation>
  </xsd:element>
</xsd:sequence>

So, I'd like to be able to type a template as this xsd:group. Is this even possible?

Answer 1

The value of the @as should contain an XPATH sequence type

Since you are constructing a sequence of two different types of elements I believe you would use element()*, which would indicate that the template will return zero or more occurrences of an element.

You could type the individual templates/functions used to produce those elements and restrict them to the specific element. For intance, element(ProductType)? would indicate zero or one ProductType element.

<xsl:template name="ProductModel" as="element()*">
  <xsl:call-template name="ProductType" />
  <xsl:call-template name="ProductId" />
</xsl:template>

<xsl:template name="ProductType" as="element(ProductType)?">
  <ProductType></ProductType>
</xsl:template>

<xsl:template name="ProductId" as="element(ProductId)?">
  <ProductId></ProductId>
</xsl:template>

EDIT: looking over the details for sequence type syntax, the definition of element is:

ElementTest ::= "element" "(" (ElementNameOrWildcard ("," TypeName "?"?)?)? ")"

The second parameter, type name, is a QName

One of the examples listed under 2.5.3 SequenceType Syntax:

element(*, po:address) refers to an element node of any name that has the type annotation po:address (or a type derived from po:address)

So, you might be able to do the following(but it would probably require a schema aware processor, like Saxon-EE):

<xsl:template name="ProductModel" as="element(*,fpml:Product.model)*">
  <xsl:call-template name="ProductType" />
  <xsl:call-template name="ProductId" />
</xsl:template>

<xsl:template name="ProductType" as="element(ProductType)?">
  <ProductType></ProductType>
</xsl:template>

<xsl:template name="ProductId" as="element(ProductId)?">
  <ProductId></ProductId>
</xsl:template>