The FSCAN Facility and FOCUS Structures

This section is a brief summary of FOCUS structures and how they affect the FSCAN facility.

FOCUS databases are organized into segments which have the following properties:

Segments consist of individual data records called segment instances, in which fields have a one-to-one correspondence with each other.
Segments relate to each other as parents and children.
A group of instances in a child segment describes one instance in a parent segment.
One parent segment may have many child segments, but a child segment may have only one parent.
A FOCUS structure has one segment from which all other segments are descended. This is called the root segment.

The diagram below represents the structure of the EMPLOYEE database:

Note the position of the segments in the structure:

The EMPINFO segment is the root segment. All other segments are descended from it.
EMPINFO has four children: the FUNDTRAN, PAYINFO, ADDRESS, and SALINFO segments.
The SALINFO segment has one child, the DEDUCT segment.

The FSCAN facility displays instances in one segment at one time. When it displays the root segment (as it will when you first enter FSCAN), it displays all the instances in the segment.

The following screen illustrates how FSCAN displays the EMPINFO segment.

FSCAN   FILE   EMPLOYEEFOCUS    A1             CHANGES :0
 
        EMP_ID      LAST_NAME  FIRST_NAME  HIRE_DATE   DEPARTMENT
        ------      ---------  ---------   --------    ----------
==      071382660   STEVENS    ALFRED      800602      PRODUCTION
==      112847612   SMITH      MARY        810701      MIS
==      117593129   JONES      DIANE       820501      MIS
==      119265415   SMITH      RICHARD     820104      PRODUCTION
==      119329144   BANNING    JOHN        820801      PRODUCTION
==      123764317   IRVING     JOAN        820104      PRODUCTION
==      126724188   ROMANS     ANTHONY     820701      PRODUCTION
==      219984371   MCCOY      JOHN        810701      MIS
==      326179357   BLACKWOOD  ROSEMARIE   820401      MIS
==      451123478   MCKNIGHT   ROGER       820202      PRODUCTION
---------------------------------INPUT---------------------------------
--
==
==>
                                                       MORE=>

Note that the screen only displays the first five fields of the first ten instances in the segment. To view the other fields and instances, use the scrolling facilities described in Scrolling the Screen.

Also note that you cannot move from one segment to another by simply scrolling. To move from a parent segment to a child segment and back again, you must use the PARENT and CHILD commands discussed in Displaying Descendant Segments: The CHILD, PARENT, and JUMP Commands.

When FSCAN displays a child segment, it displays only those instances relating to an instance in the parent segment. You can scroll back and forth to view all the instances in the group, but you cannot scroll to view the child instances of another parent. At the top of the screen, FSCAN displays up to five keys of the parent instance, and of the parent of the parent, and so on, up to the root segment.

For example, the EMPINFO segment contains the ID numbers and names of employees; its child (SALINFO) contains monthly pay instances. (Each instance lists how much each employee was paid each month.) Each group of instances in SALINFO represents all the monthly pay of one employee recorded in the EMPINFO segment. When FSCAN displays the SALINFO segment, it displays one group of instances at one time.

This is how FSCAN displays the monthly pay of Alfred Stevens, who is listed in the EMPINFO segment. Note that Mr. Stevens' employee ID (the EMPINFO key field) appears at the top of the screen:

FSCAN  FILE  EMPLOYEEFOCUS    A1               CHANGES :0
 
EMP_ID : 071382660
 
          PAY_DATE     GROSS
          --------     -----
==        820831       916.67
==        820730       916.67
==        820630       916.67
==        820528       916.67
==        820430       916.67
==        820331       916.67
==        820226       916.67
==        820129       916.67
==        811231       833.33
---------------------------------INPUT---------------------------------
--
==
 
 
==>

If you are displaying one child segment and wish to display another one, you must return to the parent and request the other child segment. For example, if you are examining Alfred Stevens' monthly pay and wish to view his salary history (contained in the segment PAYINFO), return to the EMPINFO segment and request PAYINFO information for Alfred Stevens using the CHILD command described in Displaying Descendant Segments: The CHILD, PARENT, and JUMP Commands.

The figure below shows this path schematically. The arrows show the direction you are traveling to move from the SALINFO segment to the PAYINFO segment:

Similarly, if you are displaying one group of child instances and wish to display another group within the same segment but belonging to a different instance in the parent, you must return to the parent segment and request the child segment for the other instance.

For example, suppose you are examining Alfred Stevens' monthly pay and wish to view Mary Smith's monthly pay. You must return to the EMPINFO segment and select the SALINFO segment for Mary Smith.

The figure below shows this path schematically. The arrows show the direction you are traveling to move from Alfred Stevens' monthly pay instances to Mary Smith's monthly pay instances:

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