Don't understand this piece of XML - xsd

Question

I'm trying to make an XML schema, and not having too much success. there's a construct I don't understand ... here's what I have so far for the schema, followed by the XML file I'm trying to make it for .. any suggestions?
<?xml version="1.0" encoding="utf-16"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsd:element name="CorbelFile">
<xsd:complexType>
<xsd:sequence>
<xsd:group ref="Project" minOccurs="0" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:group name="Project">
<xsd:sequence>
<xsd:element name="ADProductID"
type="xsd:string" />
<xsd:element name="ADProductID"
type="xsd:string" />
<xsd:element name="ADProductName"
type="xsd:string" />
<xsd:element name="ADProductVersion"
type="xsd:string" />
<xsd:element name="ADProjectId"
type="xsd:string" />
<xsd:element name="ADProjectName"
type="xsd:string" />
<xsd:element name="ADFileLoc"
type="xsd:string" />
<xsd:group ref="Answers"
minOccurs="0"
maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:group>
<xsd:group name="Answers">
<xsd:sequence>
<xsd:element name="var"/>
</xsd:sequence>
</xsd:group>
</xsd:schema>
XML
<?xml version="1.0" encoding="utf-16" standalone="yes"?>
<CorbelFile>
<Project>
<ADProductId>28359</ADProductId>
<ADProductName>IDP 403(b)</ADProductName>
<ADProductVersion>7.0</ADProductVersion>
<ADProjectId>00010001</ADProjectId>
<ADProjectName>Independence Dental Center PS</ADProjectName>
<ADFileLoc>C:\Program Files\Relius\Docs\dp_data\1\0\00010001.ck2</ADFileLoc>
<answers>
<Var Ld="PKGA" />
<Var Ld="BKTHead2" />
<Var Ld="SingleSpace" />
<Var Ld="MarginRagged" />
<Var Ld="SPDTimes" />
<Var Ld="BKTTimes" />
<Var Ld="PlanNameB" />
<Var Ld="ERPYEnds" />
<Var Ld="InitialEffDate" />
<Var Ld="2000SafHarEnhancMatch" />
<Var Ld="StateCollege" />
<Var Ld="CharityCorp" />
<Var Ld="ExceptEEPartTime">Independence</Var>
<Var Ld="ExceptEEStudent">Missouri</Var>
<Var Ld="ExceptEENonResAliens">11500 East 23rd Street</Var>
<Var Ld="ExceptEECollBargAgree">64052</Var>
<Var Ld="EEExclNA">[phone]</Var>
<Var Ld="NoExclElig">43-1118440</Var>
<Var Ld="ACP2000CurrentYR">001</Var>
<Var Ld="ExceptEEHR" />
<Var Ld="1YRAndHalfServReq">Profit Sharing Plan and Trust</Var>
<Var Ld="YRServReq">Independence Dental Center, Inc.</Var>
<Var Ld="Age21">INDEPENDENCE DENTAL CENTER, INC.</Var>
<Var Ld="AgeOther">PROFIT SHARING PLAN AND TRUST</Var>
<Var Ld="1stDayMonth">September 30</Var>
<Var Ld="1stDayPYNextFollowing">October 1</Var>
<Var Ld="CompExclOT">September 30</Var>
<Var Ld="CompExcl414s">October 1</Var>
<Var Ld="CompSalRed">December 12, 1963</Var>
<Var Ld="NASRA" />
<Var Ld="ACPPreYR" />
<Var Ld="QNECPY" />
<Var Ld="QNEC500HRs" />
<Var Ld="QNECYOS" />
<Var Ld="ShareDiscrYOSEndPY" />
<Var Ld="ForfeitRedERContr" />
<Var Ld="7YRGrade" />
<Var Ld="MinDistCYAftr2000">Brad Babcock</Var>
<Var Ld="MinDistCYAftr2001">Lauren Carr</Var>
<Var Ld="NServPriorEffDate" />
<Var Ld="1999SafeHarbContr">John Smith</Var>
<Var Ld="NRD1stDayMonth" />
<Var Ld="NRAPartAnnivBDay1" />
<Var Ld="NERD" />
<Var Ld="NDistrJSA" />
<Var Ld="Multi2ndERCityStateZip" />
<Var Ld="2000SafHarNonElectOthrPln" />
<Var Ld="TermDistrImmed" />
<Var Ld="YTransRoll403b" />
<Var Ld="LoansNA" />
<Var Ld="Loans10000DeMin" />
<Var Ld="LoansSRALimit" />
<Var Ld="YDirInv" />
<Var Ld="DirInvRollTrans" />
<Var Ld="HrdshipSafeHarb401k" />
<Var Ld="EmployerPhone" />
<Var Ld="NMulti2ndER" />
<Var Ld="Multi2ndERName" />
<Var Ld="YMulti3rdER" />
<Var Ld="Multi3rdERStreet" />
<Var Ld="Multi4thEIN" />
<Var Ld="Multi5thERStreet" />
<Var Ld="SumPlanOnly" />
<Var Ld="YPSBKT" />
<Var Ld="YSBJPA" />
<Var Ld="NAPriorCurrentYRTestMethP" />
<Var Ld="NHCPContrPost973Perc" />
<Var Ld="NComplyGATTUSERRASBJPATRA" />
<Var Ld="NSafeHarbMatch" />
<Var Ld="DeferBenOption" />
<Var Ld="PayOldAnnuitDate">59 1/2</Var>
<Var Ld="NAHrdshipSafeHarb401k">60th</Var>
<Var Ld="VServ3" />
<Var Ld="VServ6" />
<Var Ld="VPerc1" />
<Var Ld="VPerc6" />
<Var Ld="ACPCurrentPre97" />
<Var Ld="ACPCurrentPre98" />
<Var Ld="YDiscrMC4PercCompPost99PY" />
<Var Ld="EG_Hrdshp_Suspensn_Red_N" />
<Var Ld="EG_Suspensn_2001_NA" />
</answers>
</Project>
<Project>
<ADProductId>83</ADProductId>
<ADProductName>IDP Money Purchase/Target</ADProductName>
<ADProductVersion>2.0</ADProductVersion>
<ADProjectId>00010002</ADProjectId>
<ADProjectName>Independence Dental Center MP</ADProjectName>
<ADFileLoc>C:\Program Files\Relius\Docs\dp_data\2\0\00010002.ck2</ADFileLoc>
<answers />
</Project>
<Project>
<ADProductId>24581</ADProductId>
<ADProductName>IDP Revised SA</ADProductName>
<ADProductVersion>10.0</ADProductVersion>
<ADProjectId>000102C9</ADProjectId>
<ADProjectName>2010 - Hanover - Trustee</ADProjectName>
<ADFileLoc>C:\Program Files\Relius\Docs\dp_data\9\C\000102C9.ck2</ADFileLoc>
<answers>
<Var Ld="NShortAmendment" />
<Var Ld="PASMM" />
<Var Ld="PACorpResol" />
<Var Ld="PTimes" />
<Var Ld="SPDTimes" />
<Var Ld="CorbelClientNameA">AMERICAN FIDUCIARY CORPORATION</Var>
<Var Ld="SA401kProfitSharing" />
<Var Ld="EmployerNameA">Hanover Obstetrics & Gynecology, Inc.</Var>
<Var Ld="Corp" />
<Var Ld="EmployerStreet">135 Webster Street</Var>
<Var Ld="EmployerCity">Hanover</Var>
<Var Ld="EmployerState">Massachusetts</Var>
<Var Ld="EmployerZip">02339</Var>
<Var Ld="EmployerPhone">[phone]</Var>
<Var Ld="EIN">04-2477545</Var>
<Var Ld="PlanNumOther">001</Var>
<Var Ld="PlanNameA">Hanover Obstetrics & Gynecology, Inc.</Var>
<Var Ld="PlanNameB">401(k) Profit Sharing Plan</Var>
<Var Ld="AmendmentOne" />
<Var Ld="AmendDate">August 1, 2010</Var>
<Var Ld="NWitnessLine" />
<Var Ld="PlanAdminERAddress" />
<Var Ld="IndivTrustee" />
<Var Ld="DesignatedAmendments" />
<Var Ld="401KfeaturesNoChange" />
<Var Ld="DiscrContrNoChange" />
<Var Ld="DistributionsAmendNo" />
<Var Ld="MiscAmendYes" />
<Var Ld="NoChangeCompDefinition" />
<Var Ld="NLoans" />
<Var Ld="HCENoChange" />
<Var Ld="NElimOfFamAggreg" />
<Var Ld="AddTransRollNo" />
<Var Ld="PYFYNoChange" />
<Var Ld="ChangeTrustNameYes" />
<Var Ld="ChangedTrustee1Name">Albert Marcus, M.D.</Var>
<Var Ld="ChangedTrustee1EffDate">August 1, 2010</Var>
<Var Ld="ChangedTrustee1Removed" />
<Var Ld="MergFreezeTermNA" />
<Var Ld="NERAdopt" />
<Var Ld="RelDate" />
</answers>
</Project>

Answer 1

In Visual Studio open your xml file, go for the "XML" menu, select "Create Schema".

Answer 2

Instead of using a group, define "Var" as an element with an "Ld" attribute:
<complexType name="Var">
<annotation>
<documentation>
Description of what a Var is
</documentation>
</annotation>
<attribute name="Ld" type="string">
<annotation>
<documentation>
Description of what this attribute means
</documentation>
</annotation>
</attribute>
</complexType>
The define the list of answers:
<complexType name="Answers">
<annotation>
<documentation>
A list of Var elements
</documentation>
</annotation>
<sequence>
<element name="Var" type="Var" minOccurs="0" maxOccurs="unbounded">
<annotation>
<documentation>
The list of Var elements
</documentation>
</annotation>
</element>
</sequence>
</complexType>
Then instead of this:
<xsd:group ref="Answers"
minOccurs="0"
maxOccurs="unbounded"/>
You'd use this:
<element name="answers" type="Answers"/>
Also, a good rule of thumb is to make the default namespace match the type of file you're writing. So if you're writing a schema, put this in the root element instead and you won't have to write "xsd" prefixes everywhere:
xmlns="http://www.w3.org/2001/XMLSchema"
And it's also a good idea to create a target namespace for your schema so that your elements have an associated namespace:
targetNamespace="http://my.example.com/schema"
xmlns:mec="http://my.example.com/schema"
Which would mean your elements would be referred to as type="mec:Project" instead of just "Project" and therefore prevent any future problems when using this schema in conjunction with another one.

Answer 3

How to define an element to contain only text but also an attribute
Generally type of elements with only text content has to be xs:simpleType. In this case this causes a problem, because type definition of elements that can contain attributes (or other elements) must be xs:complexType. The solution is to use xs:simpleContent to allow text only and xs:extension to extend this type with the desired attributes.
Creating complex text-only elements
xs:simpleContent is used to derive types from other built-in or previously defined types. It requires either xs:extension or xs:restriction child element with attribute base that defines the base type (simple) that you will extend or restrict. In this case the base type can be xs:string. xs:extension or xs:restriction contains the desired new features.
<xs:element name="var">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string">
<xs:attribute name="Ld" type="xs:string" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
Several attribute definitions can added inside xs:extension - in this case we only needed one. xs:simpleContent cannot contain any element definitions, only new attributes. If the base type is not the same as any of the built-in schema datatypes, for example if the text has some length restrictions, you must define the base type as a global simple type definition and use its name in the base attribute.
Allowing text inside elements that can contain other elements is simpler: just use <xs:complexType mixed="true"> when defining the element contents.