HP System Dictionary/XL Utilities Reference Manual - Part 1 SDDBD (32256-90003)

74 Chapter8

Schema Generation Process

Database

SDDBC searches the IMAGE-DATABASE entity for the database speciﬁed in the IMAGE

command. This entity is used as the database name in the schema. The attribute value of

image-database-type is used to determine if the database is a TurboIMAGE database.

Passwords

To get the user classes and passwords for the database, SDDBC searches the

IMAGE-DATABASE contains IMAGE-CLASS relationships. The user class numbers and

passwords are obtained from the attributes class-number and password of the image-class

entity. SDDBC sorts the password information by class-number and writes the user class

numbers and passwords to the password part of the schema ﬁle.

Items

To get all the items in the database, SDDBC ﬁrst searches all the data sets related to the

speciﬁed database by ﬁnding the IMAGE-DATABASE contains IMAGE-DATASET

relationships. The record layout of the IMAGE-DATASET is then found by using the

IMAGE-DATASET contains RECORD relationships. There can be more than one record

layout per data set. If there is more than one layout for the data set, SDDBC uses the

primary record layout which is indicated by the IMAGE-DATASET contains RECORD

attribute primary-record. If there is more than one record layout and none of them are the

primary record layout, then SDDBC will use the ﬁrst record layout as retrieved from the

dictionary. If there is more than one primary record layout, SDDBC will use the ﬁrst

primary record as retrieved from the dictionary. The items are obtained by following the

RECORD contains ELEMENT relationships. The attribute element-type of the RECORD

contains ELEMENT relationship is used as the type designator of an item deﬁnition. If the

attribute back-reference is true, then the element-type attribute is retrieved from the

element entity itself.

The element entities are then retrieved, and attribute count is used as sub-item count, and

attribute byte-length is used to derive the sub-item length as follows:

Item type Byte-length Sub-item length

D,I,J,K,R n n + 1 / 2

U,X,Z n n

P n 2 * n

The sub-item length of the data item is rounded to an integral number of words in length

regardless of the type designator and its unit of measure. This is to conform with the

standards set by IMAGE/V.

To get the read and write class lists for an item deﬁnition, SDDBC searches the

ELEMENT contains IMAGE-CLASS relationships. The class list is appended next to the

data item in the item part of an item deﬁnition.

SDDBC then writes all the data items in sorted order (of item names) to the item part of

the schema ﬁle.