DTD and XSD are both used to define the structure and legal elements of an XML document, but XSD provides more robust validation capabilities. DTD has limitations in that it only supports validation of the root element, lacks namespaces and data types, and is weakly typed. In contrast, XSD supports validation of any element, uses namespaces, provides primitive and custom data types with restrictions, and is strongly typed. While DTD is suitable for small XML data, XSD is better suited for large XML documents like those used in web services and datasets due to its stronger validation features.

1. Difference between DTD and XSD
S.No DTD XSD
1 Abbreviation: Abbreviation:
DTD stands for Document Type XSD stands for Xml Schema
Definition Definition
2 Markup validation: Markup validation:
Can specify only the root element Any global element can be root. No
in the instance document. No ambiguous content support.
ambiguous content support.
3 Namespace support : Namespace support :
DTD does not support namespace XSD uses its own set of namespaces
instead it has its own set of and elements for defining the schema.
keywords for defining a schema
example:
!DOCTYPE for root tag
!ELEMENT for an element
!ATTLIST for an attribute
!ENTITY for defining variables.
4 Code reuse: Code reuse:
Poorly supported. Can use Can reuse definitions using named
parameter entities. types.
5 Datatype Support : Datatype Support :
No real datatype support. DTD Provides flexible set of datatypes.
has only #PCDATA as the data
type for the elements.(it is used 1. primitive / fundamental data types:
for string datatype) string,decimal,float,boolean
2. Custom Data types
i. complex type : a data type that
contains child elements or attributes
and
also the mixed contents
ii. simple type : a data type that
contains only values.
Provides multi-field key cross
references. No co-occurrence
constraints.
6 Datatype Validation: Datatype Validation:
In DTD, no such restrictions XSD allows us to specify restriction

2. on data .
Example: <price></price> tag. we can
write only digits here.
7 Uses: Uses:
DTD is more suitable for small XSD is used in large XML Data ex:
XML Data ADO.NET DataSets, Web Services.
ex:bookname,companyname etc.
8 Strongly / Weakly typed: Strongly / Weakly typed:
DTD is weaky typed. XML Schema is strongly typed.
DTD lacks strong typing An XML Schema can define the data
capabilities, and has no way of type of certain elements, and even
validating the content to data constrain it to within specific lengths
types. or values. This ability ensures that the
data stored in the XML document is
accurate.
9 Provisions of Inline Definitions: Provisions of Inline Definitions:
DTD allows inline definitions. XML Schema does not allow inline
definitions
This is good when working with
small files, as it allows us to
contain both the content and the
schema within the same
document, but when it comes to
larger documents, this can be a
disadvantage, as we pull content
every time we retrieve the
schema. This can lead to serious
overhead that can degrade
performance.
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