Syntax

Reading XML Schema using READ-XMLSCHEMA( ) has two distinct meanings, depending on your use case:

  • If you are creating a dynamic object, then reading XML Schema is the process of creating the definition of the dynamic object from the specified XML Schema.
  • If the object already has a definition, then reading XML Schema is the process of comparing the existing definition to the specified XML Schema. This comparison is known as verification. Since static objects cannot exist without a definition, the purpose of reading XML Schema into a static object is always verification. If a dynamic object already has its definition, then the purpose of reading XML Schema into it is also verification.

Verification allows you to test the compatibility of the object with the specified XML Schema document. If the object and XML Schema are not an exact or close match, the READ-XMLSCHEMA( ) method call fails and returns FALSE. The verification-mode parameter (described later) controls how close the match must be.

Note: The XML document must be an XML Schema written in the XML Schema Definition (XSD) language in the 2001 XML Schema namespace (http://www.w3.org/2001/XMLSchema). Non-OpenEdge applications might use XSD in many ways. The READ-XMLSCHEMA( ) method attempts to parse any XSD elements that form an obvious relational structure into ABL temp-tables and ProDataSets. However, the method might not be able to handle every XSD element generated by a non-OpenEdge source. The closer a particular XSD element conforms to what the WRITE-XMLSCHEMA( ) method creates, the more likely that the READ-XMLSCHEMA( ) method will succeed.

Here is the syntax for READ-XMLSCHEMA( ). The method returns TRUE or FALSE to indicate whether the operation was successful.

READ-XMLSCHEMA ( source-type, {file|memptr|handle|longchar}, override-default-mapping[, field-type-mapping[, verify-schema-mode]] )
source-type
A CHARACTER expression that specifies the source XML document type. Valid values are: "FILE","MEMPTR", "HANDLE", and"LONGCHAR".
file
A CHARACTER expression that specifies the name of an XML Schema file. You can specify an absolute pathname, a relative pathname (based on the current working directory), or a URL pathname. Valid URL protocols include FILE and HTTP (the HTTPS protocol is not supported). The AVM verifies that the file exists and is accessible.
memptr
A MEMPTR variable that contains the XML Schema document text. The size of the MEMPTR variable must match the size of the XML document text.
handle
A WEB-CONTEXT system handle, X-document object handle, or X-noderef object handle.
longchar
A LONGCHAR variable that contains the XML Schema document text.
override-default-mapping
A LOGICAL expression where TRUE directs the AVM to override the default mapping between XML Schema string and binary data types and ABL data types when creating ABL temp-table definition from an XML Schema. The default value is FALSE.
The XML Schema string data type maps to the ABL CHARACTER data type by default, and the XML Schema base64Binary and hexBinary data types map to the ABL RAW data type by default. If you specify TRUE, the READ-XMLSCHEMA( ) method creates a temp-table schema with CLOB and BLOB fields instead of CHARACTER and RAW fields.
If you specify the Unknown value (?), the method uses the default value of FALSE.
Note: If the temp-table or ProDataSet has an ABL definition, this option is ignored.
field-type-mapping
An optional CHARACTER expression that evaluates to a comma-separated list of field name, data type pairs using the following syntax:
field-name-1, data-type-1[, field-name-n, data-type-n ]...)
This option allows you to specify the ABL data type for a specific field from the XML Schema. Generally, this option is only used to map fields from non-ABL generated schema. When reading and writing ABL-generated XML Schema, there is little need to override field mappings because of the ABL extensions to standard XML Schema. (The ABL extensions use an identifying prefix prodata.)
field-name
The name of the specified field. For a ProDataSet object, you must qualify the field name with the buffer name from the XML Schema. That is, buffer-name.field-name.
data-type
The target ABL data type for the specified field. The data type must be a valid ABL data type, and it must be compatible with the XML Schema type based on the ABL XML data type mapping rules. For example, any XML Schema type can be mapped to ABL CHAR or CLOB, but an XML Schema dateTime can be mapped only to ABL DATE, DATETIME or DATETIME-TZ.
If you specify the Unknown value (?), the method uses the default data type.
Note: If the temp-table or ProDataSet has an ABL definition, this option is ignored.
For more information about the ABL XML data type mapping rules, see XML Schema and ABL Data Type Mappings.
verify-schema-mode
An optional CHARACTER expression that specifies the mode in which the READ-XMLSCHEMA( ) method verifies any XML Schema against an existing ABL definition. The expression must evaluate to "LOOSE" or "STRICT". The default value is "LOOSE".
Note: For a dynamic temp-table or ProDataSet temp-table buffer that does not have ABL definition (that is, the object is in the CLEAR state), this option is ignored.
The following table lists the READ-XMLSCHEMA( ) method schema verification modes.
Table 1. READ-XMLSCHEMA( ) method verification mode
For this mode . . . And this object . . . The READ-XMLSCHEMA( ) method . . .
STRICT temp-table Matches temp-table columns by name. The data type and extent of the column in the XML Schema must match those for the matching column in the temp-table. Other field attributes in the XML Schema are ignored. The XML Schema must define a field for every temp-table field and cannot define any additional fields.
ProDataSet Matches temp-tables and columns by name. There must be a temp-table defined in the XML Schema for each table of the ProDataSet. There can be no tables defined in the XML Schema that are not in the ProDataSet definition. There must be field defined in the XML Schema for each field in the temp-table, with the same data type and extent, and there can be no fields defined in the XML Schema that are not in the temp-table definition. There must also be a data relationship defined in the XML Schema for every data-relation in the ProDataSet, and there can be no data relationships defined in the XML Schema that are not defined in the ProDataSet. The field mapping between the parent and child buffers must match.
LOOSE temp-table Matches temp-table columns by name. The data type and extent of the column in the XML Schema must match those for the matching column in the temp-table. Other field attributes in the XML Schema are ignored. The XML Schema might be a subset or superset of the temp-table definition. Any columns that are not present in both the XML Schema and the temp-table are ignored.
ProDataSet Matches temp-tables and columns by name. The data type and extent of the column in the XML Schema must match those for the matching column in the temp-table. Other field attributes in the XML Schema are ignored. Data relationships are matched by parent buffer and child buffer names. For each match between a data relationship in the XML Schema that a data-relation in the ProDataSet, the field mapping must match for the parent and child buffers. The XML Schema may be a subset or superset of the ProDataSet definition. Any temp-tables, columns, or data-relations that are in the ProDataSet, but not in the XML Schema, are ignored. For a dynamic ProDataSet object, the method adds temp-tables and data-relations to the object when the temp-tables and data-relations are defined in the XML Schema, but are not members of the ProDataSet. Fields are not added to existing temp-tables. For a static ProDataSet object, any temp-tables or data-relations that are in the XML Schema, but not in the ProDataSet, are ignored.
If you specify the Unknown value (?), the method uses the default value of LOOSE.
If the XML Schema verification fails, the method generates an error message indicating the XML Schema element that caused the failure and returns FALSE.