Table of contents

Asset previews (Watson Knowledge Catalog)

If you have the required permissions, you can see a preview of the contents of many types of data assets and some types of operational assets in projects and catalogs. For data assets from files, only files with specific file extensions and mime types have previews.

Permissions to view previews

To see an asset preview, these conditions must be true:

  • You have access to the asset, either because the privacy setting for the asset is public, or you are a member of or the owner of the asset.
  • You are not blocked by any data protection rules. If you are the owner of the asset, you can’t be blocked by data protection rules.
  • If the asset has an associated connection, these conditions must also be true:
    • You are not blocked from accessing the connection by any data protection rules.
    • The username in the connection details has access to the object at the data source.

If you see a lock icon a lock icon next to the column name of a relational data asset, it means that the data in the column is masked by a data protection rule. Data protection rules can mask data by masking the original values with similarly formatted values, or by substituting the values and format of the data with meaningless values. Within a catalog, the owner of the asset is not affected by data protection rules and always sees the original values. Within a project, all project collaborators see the asset the way it looks to the person who adds it from the catalog.

Preview content for types of assets, files, and data

The content you see in a preview depends on the type of asset, file, or data.

Relational data, CSV, Avro, partitioned data files, and Parquet files
The preview includes column names, data types, data classes, and a subset of rows of data. Data classes identify the type of content in the column. Data classes are inferred automatically as part of the asset profile. For connected data, you can see when the data in the preview was last fetched from the connection and refresh the preview data in projects and catalogs by clicking Refresh.
Data connections marked with a key icon (the key symbol for private connections) are locked. If you are authorized to preview the data source, you are asked to enter your personal credentials the first time you select it. This is a one-time step that permanently unlocks the connection for you. See Adding connections to projects.
TSV files
The preview includes column names, data types, and a subset of rows of data.
PDF, text, JSON, and images
The preview shows the whole document.
Microsoft Excel documents
The preview shows the first sheet.
Folder assets
The preview shows the files and subfolders, which you can also preview.
The preview shows the whole notebook.
The preview shows information about the model.
The preview shows a snapshot of what the dashboard looks like. When you select to publish a dashboard to a catalog, you can choose to add screen captures of the dashboard with the dashboard file to the catalog. If a snapshot of the dashboard was added to the catalog, users can preview the snapshot before adding the dashboard from the catalog into another project.
COBOL copybooks and data from z/OS
Normally, accessing data from mainframe systems can be problematic because these systems have restricted access and use unique software and code. But now you can use Data Virtualization Manager for z/OS to access data and COBOL copybooks from mainframes.

Copybooks are files that describe the structure of a data for COBOL program. With virtual tables and views that are generated from COBOL copybook maps, you can import and catalog metadata from mainframes into Cloud Pak for Data as data assets and COBOL copybook assets.

Previews of data assets that are pulled from virtual tables provide you with access to the data on the mainframe computer. COBOL copybook assets get reflected in the map metadata included with the IBM Data Virtualization Facility on the mainframe computer.

After you import your metadata, you can use the data assets as the basis for any of the tasks you normally use the Cloud Pak for Data catalog for.

You can also directly view the copybook asset to examine the structure of the data in the mainframe.


  • When you import copybook assets, make sure to select a catalog as the import target. Importing into a project is not supported.
  • Scoping is not supported when importing copybook assets.

File extensions and mime types of previewed files

These types of files that contain structured data have previews:

Extension Mime type
csv text/csv
csv1 application/csv
json application/json
txt text/plain
xlsx application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
xlsb application/
xls application/
xlsm application/

These types of image files have previews:

Extension Mime type
bmp image/bmp
gif image/gif
jpg image/jpeg
jpeg image/jpeg
png image/png

These types of document files have previews:

Extension Mime type
html text/html
pdf application/pdf
txt text/plain