Excel-Friendly XML Schemas

Several characteristics make an XML schema more amenable to being mapped into Excel. First, an XML schema should have one root element. In our example in this chapter, the root element is Order. If a schema supports more than one root element, you must choose which element will be the root element when adding the XML map to the spreadsheet.

Unsupported XML Schema Constructs

Excel does not support several XML schema constructs. Table 21-1 lists these constructs.

Table 21-1. XML Schema Constructs That Are Not Supported by Excel

Construct	What It Does
<any>	Allows you to include arbitrary elements that are not declared by the schema.
<anyAttribute>	Allows you to include arbitrary attributes that are not declared by the schema.
recursion	A structure that refers to itself recursively.
abstract elements	Allows an element to be declared but never usedalso uses substitution to substitute other elements for the abstract element.
<substitutionGroup>	Allows an element to be substituted for another element.
mixed content	When XML elements are intermixed with non XML. This proves to be very useful for Word XML mapping.

Constructs That Can Be Mapped But Not Exported

There are also several things that can be mapped but the generated mappings cannot be exported as XML. You have already seen that if an XML mapping is denormalized, it cannot be exported. You also cannot export a list of items containing a second list of items. Choice elements can also not be exported.

The other general class of issues that prevents exporting is when a mapped element's relationship with another element it is related to cannot be preserved by the mapping. For more information on these types of mapping issues, consult the Excel documentation.

VSTO-Friendly Schemas

VSTO puts some additional requirements on schema mapping if you want to use a schema mapped spreadsheet with VSTO. First, you need to have a schema mapping that can be exported. Second, the schema mapping must all be within a single worksheet. Although Excel will let you map some elements of the schema to Sheet1 and other elements to Sheet2, VSTO requires that all schema mapping for a given schema be on the same sheet.

How XML Schema Data Types Are Mapped to Excel Cell Formats

As you saw earlier in this book when mapping dates, Excel can automatically pick cell formatting based on the type in the schema. When we dragged a date into Excel, Excel prompted to change the cell formatting. Table 21-2 shows how Excel maps schema types to Excel cell formatting settings.

Table 21-2. XML Schema Types and Their Corresponding Excel Cell Formatting

XML Type	Excel Formatting	XML Type	Excel Formatting
anytype	Text	int	General
anyURI	Text	integer	General
base64Binary	Text	language	Text
boolean	Boolean	long	General
byte	General	Name	Text
date	Date *3/14/2001	NCName	Text
dateTime	m/d/yyyy h:mm	negativeInteger	General
decimal	General	NMTOKEN	Text
double	General	NMTOKENS	Text
duration	Text	nonNegativeInteger	General
ENTITIES	Text	nonPositiveInteger	General
ENTITY	Text	normalizedString	Text
float	General	NOTATION	Text
gDay	Number, no decimals	positiveInteger	General
		QName	Text
gMonth	Number, no decimals	short	General
		string	Text
gMonthDay	Custom d-mmm	time	h:mm:ss
gYear	Number, no decimals	token	Text
		unsignedByte	General
gYearMonth	Custom mmm-yy	unsignedInt	General
hexBinary	Text	unsignedLong	General
ID	Text	unsignedShort	General
IDREF	Text
IDREFS	Text