Differences with SGML

The following constructs which are permitted in SGML are not allowed in XML:

Unclosed start-tags
```
<text>test<break</text>
```
Unclosed end-tags
```
<text><b>test</b</text>
```
Empty start-tags
```
<text><>test</b></text>
```
Empty end-tags
```
<text><b>test</></text>
```
Attribute values in attribute specifications entered directly rather than as literals
```
<text style=bold>test</text>
```
Attribute specifications that omit the attribute name
```
<text bold>test</text>
```