MIL-DTL-87269D
Establishment of standard identiiers, data entity relationships, and multiple path access routes to individual
data elements shall be part of the IETMDB design and construction.
3.3.3 Data maintainability. The IETMDB shall be constructed with provisions that allow incorporation
of any change to automatically update all aspects of the database affected by that change. This
data-maintainability requirement shall involve the following two kinds of changes to the IETMDB:
a. Additions to, eliminations of, or changes to individual data elements and attributes.
b. Changes to relationships including establishment of new relationships or elimination of old
relationships.
3.3.4 Additional content speciic DTDs. When speciied, additional content speciic DTDs shall be used in
addition to or instead of the content speciic DTD provided by TMSS (see 6.2e.). These DTDs shall be
incorporated into the overall CDM in accordance with the requirements of para 3.3.2.
3.4 Generic layer. The generic layer of the CDM is deined in the DTD provided by TMSS. This DTD
provides templates, which shall be used to deine content speciic elements. The generic layer includes a
deinition for each template and the attribute lists associated with the template. The DTD provides a
deinition of three other data types; primitive data elements that shall remain standard across all content
speciic applications; user interaction elements, called dialogs; and the context iltering elements, which
shall be used to provide the most appropriate information to a user. The following paragraphs describe
the components of the generic layer:
3.4.1 Templates. Templates shall be used as described in the DTD to deine elements declared in content
speciic DTDs. The generic layer shall contain ive templates: Node, Node Alternatives, Node Sequence, If
Node, and Loop Node. Each template shall have two components: (1) a set of semantic rules that govern
the template s activities and (2) a list of attributes.
3.4.1.1 Node template. All elements conforming to the node template shall provide the capability for
creating composite structures within the content speciic layer. Composite structures shall contain primitives,
links, and preconditions. When a composite structure contains other composite structures within its
content model, this implies hierarchy.
3.4.1.2 Node Alternatives (Alts) template. All elements conforming to the Node Alts template shall contain
a list of mutually exclusive nodes, only one of which shall be used at the time of presentation.
3.4.1.3 Node Sequence (Seq) template. All elements shall conform to the Node Seq template group
elements together and provide an order or presentation sequence to the elements. The elements conforming
to the Node Seq shall also allow an author to deine branching logic within the TI.
3.4.1.4 IF node template. Elements conforming to the if node template shall provide a method for
conditional branching. These elements shall use the same logic as the IF-THEN-ELSE statement in a
programming language. The "IF" part is the expression in the content model. The "THEN" part is the irst
node seq and is selected when the expression evaluates to true. The "ELSE" part is the second node seq,
which is optional in the CDM, and is selected when the expression evaluates to not true.
3.4.1.5 Loop node template. The loop node template shall provide the equivalent of a loop in a
programming language. This element shall provide the capability to create either a "FOR" loop or a
"WHILE" loop within the data. The expressions and assertions shall be developed in accordance with
this template and provide the testing criteria for the loop. The node sequence shall contain the actual
elements to be repeated within the loop.
3.4.2 Relational links. Elements shall have relationships to other elements in the TI, when applicable.
These relationships shall be represented through two or more link ends. The link element shall provide the
capability to show the relationship between several elements. The contractor shall include the speciic
cross-references to elements within the IETMDB as well as information sources outside the IETMDB.
3.4.2.1 Links to reduce redundancy. Links shall be used to reduce the number of redundant elements by
referencing common elements. The templates deined within the generic layer CDM DTD shall deine
attributes to reduce redundant elements.
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