对于给定的 XML 文件，此 DTD 是否错误答案

【问题标题】：Is this DTD wrong for the given XML file对于给定的 XML 文件，此 DTD 是否错误
【发布时间】：2018-08-19 00:38:42
【问题描述】：

XML（来自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>

对于上面的 XML 代码，我尝试了如下的 DTD，但我无法验证它。请检查我的 DTD 有什么问题。需要在 DTD 中进行哪些更改才能验证 XML 代码而不会出现任何错误？

【问题讨论】：

请编辑您的问题以包含 XML 文档（不要将其添加为链接）、验证 XML 文档的代码或命令以及您收到的完整错误消息。

标签： xml dtd xml-validation

【解决方案1】：

由于 gender、description（product 元素）和 image 的 ATTLIST 声明，您的 DTD 无效。 enumerations 中的值不应被引用。

此外，值应该是有效的NMTOKEN（名称标记）类型，这意味着它们不能包含空格（因此Extra Large 需要在两个DTD 中变为ExtraLarge、Extra_Large 等和 XML 实例）。

因此，要修改 DTD 以使 XML 有效，这些 ATTLIST 声明需要更改为：

<!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>

请注意，我将属性设为必需 (#REQUIRED)，但您可以将它们设为 #IMPLIED（可选）或给它们一个默认值（将值括在引号中）。请参阅https://www.w3.org/TR/REC-xml/#sec-attr-defaults 了解更多信息。

您还需要将description 属性值从“超大”更改。

另一件事;在您的 XML 中，您使用 "Men's" 和 "Women's" 作为 gender 属性的值。您需要将它们更改为“男士”和“女士”。

我还注意到您在product 元素的属性中使用了默认值。这没有意义。当您有第二个产品不是“开衫毛衣”时会发生什么？

我认为您应该将这些声明更改为：

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

请注意，我将这两个声明合并为一个，并进行了格式化以提高可读性。这不是必需的，但在我看来确实更容易阅读。

最后一件事；在color_swatch 上枚举image 也没有意义。您必须列出其中列出的每种产品的每张图片。也许将其更改为：

<!ATTLIST color_swatch image CDATA #REQUIRED>

更新的 DTD（还将 ATTLIST 声明移到相应的 ELEMENT 声明下。这只是个人喜好。）：

<!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>

【讨论】：