FAQ
|
Q. |
Why use OMG CWM and XMI XML? |
|
A. |
OMG CWM/XMI XML was chosen for MDS as it is a standards-based effort whose stated purpose is to “enable easy interchange of metadata between data warehousing tools and metadata repositories in distributed heterogeneous environments.” All serious tools should provide an XML export using CWM/XMI even if they continue to use proprietary export formats. |
|
Q. |
Where do imported objects go? |
|
A. |
All objects go into classes of the MDS CWM_Metamodel. The one-and-only root or top-level object is imported into either the CWMRDB_Catalog class or CWM_Model class. All other objects in the import can be found as destination objects of the root object. |
|
Q. |
The MDS MetaXML utility only recognizes XML in its native schema format, so how is it importing CWM/XMI XML? |
|
A. |
MetaXML is not directly importing CWM/XMI XML. A transformation file is applied first, creating a new XML file (designated as the “t_” file in the confirm-import message). The transformed file is in MetaXML schema format and is handed over to MetaXML to import. For more information, see “Technical Details” on page 255. |
|
Q. |
The import does not identify which tool the metadata comes from. What if I want to include this information for the MDS import? |
|
A. |
Consider adding user-defined properties to the CWMRDB_Catalog class using MetaBrowse or MetaXML. After the import, you can use MetaBrowse to update the appropriate CWMRDB_Catalog object and add values to its user-defined properties. |
To track a set of imported objects, consider using an MDS label. After the import, use MetaBrowse to choose the appropriate CWMRDB_Catalog object from the import and apply an MDS label with propagation. The label is then applied to all imported objects.
Note: When you add user-defined properties to a CWM_Metamodel class, use MetaXML to export the metamodel to a file, thereby saving your changes for future reference.
|
Q. |
Can I export tool objects from MDS repository into my tool (referred to as a “round-trip”)? |
|
A. |
Yes, provided your tool can import CWM/XMI XML. All tools listed in Table 178 on page 244 provide import functionality. However, there is no GUI interface for the MDS part of this task. See “Technical Details” on page 255 for information on performing an MDS export and the steps for generating CWM/XMI XML for the tools. |
|
Q. |
Can I modify imported metadata? |
|
A. |
Yes. Imported objects are like other metadata objects in the MDS repository. Updates are permitted as long as you have the proper privileges. |
|
Q. |
If I change imported metadata, are the changes reflected when I round-trip back to my tool? |
|
A. |
That depends. All MDS objects have several common properties that are not part of the CWM, for example the Description property. If you add descriptions to imported MDS objects and then export them, your Description text appears in the exported XML. However, the XSLT that converts the MDS XML back to CWM/XMI XML format does not use the Description field, so your descriptions will be lost during that step of the process. |
On the other hand, if you modify the value of a property from the original CWM/XMI XML, the MetaXML export will reflect the change, and the XSLT will preserve it, allowing the tool to import the change. It is your responsibility to make sure that your change does not break the tool’s expectations or internal rules. Otherwise, the tool import may fail, the tool execution may produce errors, or your data may “merely” be inconsistent).
|
Q. |
What happens to the XML file exported from my tool and the resulting transformed XML file? |
|
A. |
Nothing. The original file is used in read-only mode and is never altered. The transformed file is placed in the same directory as the original file and not touched after the import. You may delete either or neither file as desired. You may also re-import the transformed or original file. |
|
Q. |
Can an MDS CWM_Metamodel be created before doing a CWM import? |
|
A. |
Yes. The file containing the metamodel definition is a regular XML representation using a schema native to MetaXML. It can be imported by MetaXML at any time, the same as any other XML file. It is located in the tools folder of the MDS installation and is named CWM_Metamodel.xml. |
|
Q. |
What if I import the same CWM RDBMS::Catalog a second time? |
|
A. |
You get a new set of objects, regardless of whether you deleted the first import. This behavior is consistent with current MetaXML behavior when the “action” is “add,” which is how the transformed XML is created. |
|
Q. |
Why can I not export all the metadata out of my tool? |
|
A. |
You can export whatever the tool allows. However, unless the tool exports its metadata in CWM/XMI format, MDS will not be able to load it. The XML Bridge is based on the CWM/XMI standard provided by the OMG, so metadata exported in non-standard format cannot be imported. |
Note: A tool may not allow an export of its proprietary metadata in a standards-based format.
|
Q. |
What metadata is exported from a tool and imported into MDS? What tool metadata does MDS support? |
|
A. |
XML Bridge imports all tool metadata from an exported CWM/XMI file and has no control of what metadata a tool chooses to export in that format. Consult your tool vendor for specifics on what is exported by their tool. |
|
Q. |
I have XML files not in CWM/XMI format, but for which I can produce XSLT to transform them into MetaXML schema. Can I use XML Bridge to import them as well? |
|
A. |
Yes. See “Technical Details” on page 255. |
|
Q. |
I have a batch environment I would like to use to do XML Bridge imports into MDS. Is that possible? |
|
A. |
Yes, at least from the MDS side of the exchange. After you have exported the tool’s CWM/XMI XML to a file, MDS provides a simple “batch” way to transform the XML into MetaXML schema. For details, see “Technical Details” on page 255. |