對於給定的 XML 文件，此 DTD 是否錯誤

Question

XML （來自https://github.com/SMAPPNYU/ProgrammerGroup/blob/master/LargeDataSets/sample-xml.xml ）

<?xml version="1.0"?>
<?xml-stylesheet href="catalog.xsl" type="text/xsl"?>
<!DOCTYPE catalog SYSTEM "catalog.dtd">
<catalog>
    <product description="Cardigan Sweater" product_image="cardigan.jpg">
        <catalog_item gender="Men's">
            <item_number>QWZ5671</item_number>
            <price>39.95</price>
            <size description="Medium">
                <color_swatch image="red_cardigan.jpg">Red</color_swatch>
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
            </size>
            <size description="Large">
                <color_swatch image="red_cardigan.jpg">Red</color_swatch>
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
            </size>
        </catalog_item>
        <catalog_item gender="Women's">
            <item_number>RRX9856</item_number>
            <price>42.50</price>
            <size description="Small">
                <color_swatch image="red_cardigan.jpg">Red</color_swatch>
                <color_swatch image="navy_cardigan.jpg">Navy</color_swatch>
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
            </size>
            <size description="Medium">
                <color_swatch image="red_cardigan.jpg">Red</color_swatch>
                <color_swatch image="navy_cardigan.jpg">Navy</color_swatch>
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
                <color_swatch image="black_cardigan.jpg">Black</color_swatch>
            </size>
            <size description="Large">
                <color_swatch image="navy_cardigan.jpg">Navy</color_swatch>
                <color_swatch image="black_cardigan.jpg">Black</color_swatch>
            </size>
            <size description="Extra Large">
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
                <color_swatch image="black_cardigan.jpg">Black</color_swatch>
            </size>
        </catalog_item>
    </product>
</catalog>

DTD

<!ELEMENT catalog (product)>
<!ELEMENT product (catalog_item+)>
<!ELEMENT catalog_item (item_number,price,size+)>
<!ELEMENT size (color_swatch+)>
<!ELEMENT item_number (#PCDATA)>
<!ELEMENT price (#PCDATA)>
<!ELEMENT color_swatch (#PCDATA)>


<!ATTLIST product description "Cardigan Sweater" CDATA>
<!ATTLIST product product_image "cardigan.jpg" CDATA>
<!ATTLIST catalog_item gender ("Mens"|"Womens") CDATA>
<!ATTLIST size description ("Small"|"Medium"|"Large"|"Extra Large") CDATA>
<!ATTLIST color_swatch image ("red_cardigan.jpg"|"burgundy_cardigan.jpg"|"navy_cardigan.jpg"|"black_cardigan.jpg") CDATA>

---

對於上面的 XML 代碼，我嘗試了如下 DTD，但我無法驗證它。 請檢查我的 DTD 有什么問題。 需要在 DTD 中進行哪些更改才能驗證 XML 代碼而不會出現任何錯誤？

Answer 1

由於針對gender 、 description （ product元素）和image的 ATTLIST 聲明，您的 DTD 無效。 不應引用枚舉中的值。

此外，這些值應該是有效的NMTOKEN （名稱標記）類型，這意味着它們不能包含空格（因此Extra Large在 DTD 和 XML 實例中都需要變為ExtraLarge 、 Extra_Large等）。

因此，要修改 DTD 以使 XML 有效，這些 ATTLIST 聲明需要更改為：

<!ATTLIST catalog_item gender (Mens|Womens) #REQUIRED>
<!ATTLIST size description (Small|Medium|Large|ExtraLarge) #REQUIRED>
<!ATTLIST color_swatch image (red_cardigan.jpg|burgundy_cardigan.jpg|navy_cardigan.jpg|black_cardigan.jpg) #REQUIRED>

請注意，我將屬性#REQUIRED必需 ( #REQUIRED )，但您可以將它們#IMPLIED （可選）或給它們一個默認值（將值括在引號中）。 有關更多信息，請參閱https://www.w3.org/TR/REC-xml/#sec-attr-defaults 。

您還需要從“Extra Large”更改description屬性值。

另一件事; 在您的 XML 中，您使用“Men's”和“Women's”作為gender屬性的值。 您需要將它們更改為“男士”和“女士”。

我還注意到您在product元素的屬性中使用了默認值。 這沒有意義。 當您擁有不是“開衫毛衣”的第二款產品時會發生什么？

我認為您應該將這些聲明更改為：

<!ATTLIST product 
    description   CDATA #REQUIRED 
    product_image CDATA #REQUIRED>

請注意，我將兩個聲明合二為一並進行了格式化以提高可讀性。 這不是必需的，但在我看來確實使閱讀更容易。

最后一件事; 在color_swatch上枚舉image也沒有意義。 您必須擁有其中列出的每個產品的每個圖像。 也許將其更改為：

<!ATTLIST color_swatch image CDATA #REQUIRED>

更新了 DTD （也將 ATTLIST 聲明移到了相應的 ELEMENT 聲明下。這只是個人偏好。）：

<!ELEMENT catalog (product)>

<!ELEMENT product (catalog_item+)>
<!ATTLIST product 
    description   CDATA #REQUIRED 
    product_image CDATA #REQUIRED>

<!ELEMENT catalog_item (item_number,price,size+)>
<!ATTLIST catalog_item gender (Mens|Womens) #REQUIRED>

<!ELEMENT size (color_swatch+)>
<!ATTLIST size description (Small|Medium|Large|ExtraLarge) #REQUIRED>

<!ELEMENT item_number (#PCDATA)>
<!ELEMENT price (#PCDATA)>

<!ELEMENT color_swatch (#PCDATA)>
<!ATTLIST color_swatch image CDATA #REQUIRED>

更新的 XML

<?xml version="1.0"?>
<?xml-stylesheet href="catalog.xsl" type="text/xsl"?>
<!DOCTYPE catalog SYSTEM "catalog.dtd">
<catalog>
    <product description="Cardigan Sweater" product_image="cardigan.jpg">
        <catalog_item gender="Mens">
            <item_number>QWZ5671</item_number>
            <price>39.95</price>
            <size description="Medium">
                <color_swatch image="red_cardigan.jpg">Red</color_swatch>
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
            </size>
            <size description="Large">
                <color_swatch image="red_cardigan.jpg">Red</color_swatch>
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
            </size>
        </catalog_item>
        <catalog_item gender="Womens">
            <item_number>RRX9856</item_number>
            <price>42.50</price>
            <size description="Small">
                <color_swatch image="red_cardigan.jpg">Red</color_swatch>
                <color_swatch image="navy_cardigan.jpg">Navy</color_swatch>
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
            </size>
            <size description="Medium">
                <color_swatch image="red_cardigan.jpg">Red</color_swatch>
                <color_swatch image="navy_cardigan.jpg">Navy</color_swatch>
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
                <color_swatch image="black_cardigan.jpg">Black</color_swatch>
            </size>
            <size description="Large">
                <color_swatch image="navy_cardigan.jpg">Navy</color_swatch>
                <color_swatch image="black_cardigan.jpg">Black</color_swatch>
            </size>
            <size description="ExtraLarge">
                <color_swatch image="burgundy_cardigan.jpg">Burgundy</color_swatch>
                <color_swatch image="black_cardigan.jpg">Black</color_swatch>
            </size>
        </catalog_item>
    </product>
</catalog>