External Entities are a list of other schemas that the DTD will use.

An External Entity is generally called by a XML notation (see XML notation (DTDs only)) in the DTD. An external entity is represented solely by a definition within the encyclopedia; there are no graphical symbols on a diagram that represent it.

The general steps for modeling and generating a DTD for an external entity are:

See XML notation (DTDs only) for details on the steps above.

According to DTD specifications, the SYSTEM keyword is generally intended for private DTDs used by a single author or group.

The System field holds the location (path name or url) of the external file. For example:

The DTD that is generated will contain the SYSTEM keyword followed by the specified path and file name, for example:

PUBLIC is an XML keyword indicating that the DTD is intended for broad use. When the PUBLIC keyword is used, you must also specify a name for the DTD.

If you want to use the PUBLIC identifier instead of the SYSTEM identifier, fill in the Public Name property. If the system sees a value in the Public Name field, the PUBLIC identifier is used instead of the SYSTEM identifier in the generated DTD, for example, if the following properties were set for an external entity named jpeg:

System: http:\\www.unicomsi.com\products\product.jpg

Product Name: Product JPEG

the following DTD code would be produced:

Specify the name of the XML notation (see XML notation (DTDs only)) that calls the External Entity.

Text in the Comments field will be generated into the schema file but will be formatted as follows:

Processing Instructions are passed to an application. They typically contain a declaration of the target application and whatever instructions the application needs to process the XML schema.

Text in the Description field does not get generated to a DTD, but is generated to a BizTalk schema. You may enter a description of the modeling element, or its use in the schema. The description can be included in a report. By default, it is included in HTML reports.

Specifies one and only one schema (see What is an XML schema?) that will be used throughout the diagram, and/or the XML Schema definition that XML elements (see XML element) and attributes are keyed to. Note that all elements and element attributes created on the diagram will default to this schema name. Attribute and element symbols may be keyed to one and only one schema. If the schema is renamed, all elements and attributes that use it will be rekeyed to the new name. “Names” may be the same as long as they are keyed to different schemas.

The attribute and element instances will use the diagram's schema by default, however, this is not required. Element and attribute symbols using schema outside of the diagram’s will display with dotted borders.