#error is the preprocessor directive which produces compile time error messages. These directives are most useful for detecting programmer inconsistencies and violation of constraints during preprocessing.

A valid XML document, in addition to being well formed, conforms to all the constraints imposed by a DTD. It does not contain any tags that are not permitted by the DTD, and the order of the tags conforms to the DTD's specifications.

 Redundancy is controlled.
 Unauthorised access is restricted.
 Providing multiple user interfaces.
 Enforcing integrity constraints.
 Providing backup and recovery.

Extension -It is the number of tuples present in a table at any instance. This is time dependent.

Intension -It is a constant value that gives the name, structure of table and the constraints laid on it.

A relation is said to be in DKNF if all constraints and dependencies that should hold on the the constraint can be enforced by simply enforcing the domain constraint and key constraint on the relation.

A JSP page written in XML syntax and subject to the constraints of XML documents.

Document type definition. An optional part of the XML document prolog, as specified by the XML standard. The DTD specifies

constraints on the valid tags and tag sequences that can be in the document. The DTD has a number of shortcomings, however,

and this has led to various schema proposals. For example, the DTD entry says that the XML

element called username contains parsed character data-that is, text alone, with no other structural elements under it. The

DTD includes both the local subset, defined in the current file, and the external subset, which consists of the definitions

contained in external DTD files that are referenced in the local subset using a parameter entity.

The methods by which interactions with resources are limited to collections of users or programs for the purpose of enforcing

integrity, confidentiality, or availability constraints.

Dataset.Clone() will copy just the dataset structure including all the datatables, schemas, relations and constraints; it will not copy the data. Dataset.Copy() will copy both dataset structure and data.