FTAM/9000 Programmer's Guide

442 Chapter 11

Document Types and Constraint Sets

Constraint Sets

Every application needs a speciﬁc set of ﬁle structures, and any real

system is likely to support only a limited range of ﬁle types, with

restrictions on the ways you can modify ﬁles. Constraint sets express

these limitations by restricting the following items.

• Range of allowable ﬁle structures

• Ways in which basic access actions can modify the structure

Constraint sets restrict (reduce) the ﬁle model. These sets help you

efﬁciently model the type of ﬁle you are accessing.

The constraints sets supported by HP–UX FTAM are Unstructured and

Sequential Flat.

Each constraint set consists of the following items.

• A statement of the intended ﬁeld of application

• A constraint set descriptor for reference in documentation

• Constraint set identiﬁer for reference in the FTAM protocol

• Constraints on the node names

• Set of valid ﬁle access actions

• Qualiﬁed actions when writing to the ﬁle

• Set of ﬁle access contexts in which the ﬁle can be read

• State of the ﬁle when created

• FADU located immediately after the ﬁle is opened

• Deﬁnitions of “beginning of ﬁle” and “end of ﬁle”

• Manner in which you read from or write to the whole ﬁle

• General constraints on how you can modify the structure

Unstructured Single, un-named data unit

Sequential Flat Series of un-named data units