Introduction to Attributes

This section describes attributes associated with elements declared in and specific to the NCBI Historical DTD; an attribute previously declared in the Book DTD or base Suite has not been included, unless:

Although the attributes are declared in several modules, they are described here in alphabetical order of their tag names (i.e., attribute type names). The tag name is the shorter machine-readable name used in tagged documents, DTD fragments and schemas, and by software; for example, the tag name “alt-term-type” is used for the attribute named “Type of Alternate Term”.

Each attribute is described by a separate HTML page, where the heading for the page displays the attribute’s tag name followed by its longer descriptive name. The rest of the attribute description page discusses aspects of the attribute, its usage, and the elements to which it can be attached. These sections within the page always appear in the following order although any given attribute description may not contain all the sections:


This section contains a narrative description of the attribute. This is not a formal dictionary definition, but more an explanation of what the attribute name means, what type of information it provides, or how it can be used.


This section discusses expected uses for the attribute, such as when or why it might be used or how to determine its value. (See also the similar section Remarks, which describes additional aspects of the attribute.)


This section provides additional information about the attribute, such as similar or contrasting attributes, processing information, or material about the base element . (See also the similar section Usage, which describes when, why, or how to use the attribute.)

Conversion Notes are usage instructions aimed at persons converting from another journal article tag set to this one, for example, information concerning the problems associated with embedding TeX or LaTeX in XML and the need, therefore, to surround TeX or LaTeX with a CDATA section.

Implementor’s Notes are instructions written to persons creating or maintaining DTDs or schemas based on the Suite.


This section performs three functions: 1) naming the elements which can take the attribute, 2) describing the specific values and defaults for the attribute, and 3) optionally providing a list of suggested values for those attributes whose value is any character data (i.e., not a specific list of values).

Elements — The elements that may take the attribute are named following the phrase “In elements:”. For each element, both the tag name (the shorter element type name) and the longer descriptive name are given.

If the attribute can be used in more than one way, or with several slightly different meanings, there will be more than one “In elements:” section. Each “In elements:” section is followed by a value table that describes the attribute’s values when it is used with the specific elements just listed. For example, the attribute may have exactly the same meaning whenever it is used, but sometimes it is required while other times it is optional, so there will be two “In elements:” sections, one naming all the elements for which the attribute is required, and one naming all the elements for which the attribute is optional.

Values — Following each “In elements:” section is an Attribute Value Table that lists the possible values of the attribute and explains selected values. When the attribute originates in the NCBI Historical DTD, the Book DTD, or the base Suite, the Values section also explains the meaning of each value. Attributes defined in PUBLIC tag sets that have been incorporated into the Book or Historical Tag Set or base Suite (such as the MathML Tag Set) do not have their values explained, since those values are not under control of these DTDs or the base Suite and may change.

The Attribute Value Table typically contains two columns although a third column titled “Behavior” may be present. Each row in the table describes one value, where:

  • The entry in the column titled “Value” names or describes the value,
  • The entry in the column titled “Meaning” explains the meaning of the attribute value or describes potential content for the value, and
  • Where present, the entry in the column titled “Behavior” describes what an XML application might do with the attribute value.

The last row of the table begins with the word “Restriction:”. This row indicates whether the attribute must be supplied when the relevant element is used or is optional and may be supplied. A default value, if any exists, is also provided.

Suggested Values — For those attributes whose value is defined as text (letters, numbers, or special characters), neither DTD enforces any particular value(s), but a list of suggested values may be provided.