database¶

The Dismod_at Database Tables¶

Comment Columns and Tables¶

Any table (in this database) may have any number of columns with names that begin with the two characters c_ . These are comment columns and are ignored by dismod_at . In addition, tables with a names beginning with c_ are also considered comments and are ignored by dismod_at .

Primary Key¶

If table_name is a table (in this database), its first column has name table_name _ id that is the primary key for the table. The values in this column are integer , start at zero and increment by one for each row in the table.

Name Column¶

Suppose that table_name is a table (in this database), and the column table_name _ name exists. In this case, the values in this column are text must be unique; i.e., the names can act as substitutes for the primary key. The names are intended to be easier for a human to remember than the ids.

Foreign Key¶

If this is the name of a table its primary key is the column this _ id . If this primary key is used in another table it is called a foreign key (in the other table). The name of the column in the other table will be this _ id or it will end with _ this _ id . A value in the foreign key column must also appear in the corresponding primary key column, or it must be null .

parent¶

Note that the column parent is a primary key value for the node table ; i.e, node_id . Note that this column is not named node_id nor does it end in _ node_id . This is not an exception because the parent column is itself in the node table and hence this is not a foreign key.

Null¶

It is an error for a value to be null unless the documentation for the corresponding column specifies a meaning for this case. Lower and upper bounds are an exception to this rule (see below).

Bounds¶

If a lower (upper) bound is null , it is interpreted as minus (plus) infinity.

Integer¶

The minimum integer (negative integer with the largest absolute value) is used to represent a null integer value in a table. An error message will be generated if the minimum integer appears in a table that is read by dismod_at.

Text can be Null, not Empty¶

The empty string is used to represent a null text value in a table. An error message will be generated if the empty string appears in a text field that is read by dismod_at.

Real Can be Null, not Nan¶

If a real value is null , it is represented as nan . An error message will be generated if the value nan appears in a table that is read by dismod_at.

Type Names¶

The types in this database are integer , real and text . The type names INTEGER , REAL , and TEXT can also be used.

Contents¶

Name	Title
input	Tables That Are Only Used as Inputs
data_flow	The Dismod_at Data Flow