ShipStation has an XML API (PDF). Unfornately, because of poor PDF formatting, its impossible to properly copy-paste the XML validation schema. The following is the properly formated schema (as far as I can tell). Save it as a .xsd file and use it to validate your app’s output.
The email regular expression may change due to your language of choice. Originally, the PDF used:
([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+```
However, PHP didn’t like the \@ so I changed it to @. Your mileage may vary.
<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="http://example.com/XMLSchema/1.0" targetNamespace="http://example.com/XMLSchema/1.0" elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="Orders">
<xs:complexType>
<xs:sequence>
<xs:element name="Order" maxOccurs="unbounded" minOccurs="0">
<xs:complexType>
<xs:all>
<xs:element type="String50" name="OrderID" minOccurs="0"/>
<xs:element type="String50" name="OrderNumber"/>
<xs:element type="DateTime" name="OrderDate"/>
<xs:element type="String50" name="OrderStatus"/>
<xs:element type="DateTime" name="LastModified"/>
<xs:element type="String100" name="ShippingMethod" minOccurs="0"/>
<xs:element type="String50" name="PaymentMethod" minOccurs="0"/>
<xs:element type="xs:float" name="OrderTotal"/>
<xs:element type="xs:float" name="TaxAmount" minOccurs="0"/>
<xs:element type="xs:float" name="ShippingAmount" minOccurs="0"/>
<xs:element type="String1000" name="CustomerNotes" minOccurs="0"/>
<xs:element type="String1000" name="InternalNotes" minOccurs="0"/>
<xs:element type="xs:boolean" name="Gift" minOccurs="0"/>
<xs:element type="String1000" name="GiftMessage" minOccurs="0"/>
<xs:element type="String100" name="CustomField1" minOccurs="0"/>
<xs:element type="String100" name="CustomField2" minOccurs="0"/>
<xs:element type="String100" name="CustomField3" minOccurs="0"/>
<xs:element name="Customer">
<xs:complexType>
<xs:all>
<xs:element type="String50" name="CustomerCode"/>
<xs:element name="BillTo">
<xs:complexType>
<xs:all>
<xs:element type="String100" name="Name"/>
<xs:element type="String100" name="Company" minOccurs="0"/>
<xs:element type="String50" name="Phone" minOccurs="0"/>
<xs:element type="Email" name="Email" minOccurs="0"/>
</xs:all>
</xs:complexType>
</xs:element>
<xs:element name="ShipTo">
<xs:complexType>
<xs:all>
<xs:element type="String100" name="Name"/>
<xs:element type="String100" name="Company" minOccurs="0"/>
<xs:element type="String100" name="Address1"/>
<xs:element type="String100" name="Address2" minOccurs="0"/>
<xs:element type="String100" name="City"/>
<xs:element type="String100" name="State"/>
<xs:element type="String50" name="PostalCode" minOccurs="0"/>
<xs:element type="StringExactly2" name="Country"/>
<xs:element type="String50" name="Phone" minOccurs="0"/>
</xs:all>
</xs:complexType>
</xs:element>
</xs:all>
</xs:complexType>
</xs:element>
<xs:element name="Items">
<xs:complexType>
<xs:sequence>
<xs:element name="Item" maxOccurs="unbounded" minOccurs="0">
<xs:complexType>
<xs:all>
<xs:element type="String50" name="LineItemID" minOccurs="0"/>
<xs:element type="String100" name="SKU"/>
<xs:element type="String200" name="Name"/>
<xs:element type="xs:boolean" name="Adjustment" minOccurs="0"/>
<xs:element type="xs:anyURI" name="ImageUrl" minOccurs="0"/>
<xs:element type="xs:float" name="Weight" minOccurs="0"/>
<xs:element name="WeightUnits" minOccurs="0">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:pattern value="pound|pounds|lb|lbs|gram|grams|gm|oz|ounces|Pound|Pounds|Lb|Lbs|Gram|Grams|Gm|Oz|Ounces|POUND|POUNDS|LB|LBS|GRAM|GRAMS|GM|OZ|OUNCES"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
<xs:element type="xs:byte" name="Quantity"/>
<xs:element type="xs:float" name="UnitPrice"/>
<xs:element type="String100" name="Location"/>
<xs:element name="Options" minOccurs="0">
<xs:complexType>
<xs:sequence>
<xs:element name="Option" maxOccurs="10" minOccurs="0">
<xs:complexType>
<xs:all>
<xs:element type="String30" name="Name"/>
<xs:element type="String30" name="Value"/>
<xs:element type="xs:float" name="Weight" minOccurs="0"/>
</xs:all>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:all>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:all>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute type="xs:short" name="pages"/>
</xs:complexType>
</xs:element>
<xs:simpleType name="DateTime">
<xs:restriction base="xs:string">
<xs:pattern value="[0-9][0-9]?/[0-9][0-9]?/[0-9][0-9][0-9]?[0-9]? [0-9][0-9]?:[0-9][0-9]?:?[0-9]?[0-9]?.?[aApP]?[mM]?"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="Email">
<xs:restriction base="xs:string">
<xs:pattern value="([a-zA-Z0-9_\.\-])+@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="StringExactly2">
<xs:restriction base="xs:string">
<xs:minLength value="2"/>
<xs:maxLength value="2"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="String30">
<xs:restriction base="xs:string">
<xs:maxLength value="30"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="String50">
<xs:restriction base="xs:string">
<xs:maxLength value="50"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="String100">
<xs:restriction base="xs:string">
<xs:maxLength value="100"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="String200">
<xs:restriction base="xs:string">
<xs:maxLength value="200"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="String1000">
<xs:restriction base="xs:string">
<xs:maxLength value="1000"/>
</xs:restriction>
</xs:simpleType>
</xs:schema>