Understanding work object attachments
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A work object attachment identifies a named file, screen shot
image, URL or text note that a user or an activity has associated with a
work object. On the standard harness
rule Perform and Review forms, a paper clip button 
provides access to review or add attachments.
The system stores attachments in instances of these concrete classes, subclasses of the Data-Work Attach- class:
Your application can include additional custom attachment types.
By default, work object attachments are stored as rows of the
pc_data_workattach table. Note that attachments are not
stored in the same database table as the work objects themselves.
When a user designates a file as an attachment, the system uploads a copy of the file and links it to the history of the work object. The system saves attachments for correspondence in HTML format (HTM file type) even if a user edited the correspondence with Microsoft Word. If the correspondence includes embedded images or other embedded objects, the attachment is saved as a ZIP archive (ZIP file type) containing the objects and the HTM file. The system converts the ZIP file internally into characters using Base64 encoding.
The description text (Subject field) of a file attachment is limited to 60 characters. B-22661
By default, file attachments are restricted to 1 gigabyte 25 megabytes in size.
You can set a larger or smaller limit with the prconfig.xml
file setting:
<env name="Initialization/MaximumFileUploadSizeMB" value="nn" />
where nn is the size in megabytes. (In V5.5 and earlier releases, the default limit was 25MB.)
If a user accesses the Process Commander server with the HTTPS protocol
(rather than HTTP), this may block certain download operations from the
server to the workstation. For details and suggestions, see Pega
Developer Network article 
PRKB-17997 Troubleshooting:
"Internet Explorer cannot download " messages (Tomcat with
SSL).
Optionally, you can choose to store file attachments for an application in an external content management system such as Alfresco. This capability requires the optional Pega-Connect RuleSet. V6.1SP2
URL and URI attachments can provide flexibility and power while
requiring little storage. A URL can point to a document or file on an
intranet or the World Wide Web. A URL can also cause Process Commander to
execute an activity in your application; the activity can search or
retrieve a document or file, call an external system, and so on. See Pega
Developer Network article PRKB-16586 Linking to external
documents versus importing them as work object attachments.
A user can capture a screen image of any open window as a JPG file, known as a screen shot attachment. The JPG file is stored internally as characters using Base64 encoding. Use the Advanced View of the standard History and Attachments display to enter screen shot attachments
A user with a scanner attached to her workstation can use the Image Viewer tool to scan documents and attach them as TIFF image files to work objects. The standard Work-.AttachFromScanner local flow action starts this operation. The system converts the TIFF file into characters using Base64 encoding.
Use the Advanced View of the standard History and Attachments display to enter screen shot attachments.
Files received from any source might contain computer viruses. You can connect your application's processing of work object attachments to an external virus-checking module. Virus checking occurs before the system saves the attachment to the database. Override the standard extension point activity Data-WorkAttach-File.CallVirusCheck to call the checker and modify processing by the flow rule to handle files reported to contain viruses. C-2417 ECKSM The virus check module can be a Java routine or (when Process Commander is hosted on Microsoft Windows) in a Windows DLL file.
While the number of attachments you can add to a work object is unlimited, the standard list view rule Link-Attachment.AttachmentList.ALL displays only up to 100 attachments. You can override this rule if necessary. CLINIC 7/19/2005
If the "Index Attachments" checkbox is checked in the Search gadget of the System landing page (
> System > Settings > Search), a search of work objects in a composite User portal can include searching the contents of text-file attachments for a specified word or text string. See Understanding full-text search.wetma 4-1-10
Process Commander provides two approaches to convert Word DOC files to Portable Document (PDF) formats. For each approach, the original DOC file and the converted PDF file become two file attachments, typically of separate categories:
To convert in the background: C-2438
To convert in the foreground, include the standard flow action .Work-.ConvertAttachmenttoPDF as a local flow action in appropriate assignments in the flow rule. Users must select this flow action, complete the form, and wait for workstation conversion.
You can support attachments with attachment category rules to control the user's ability to add, view, edit, or delete attachments. For more information, see Attachment category.
You can configure your application to store attachments of type file in an external content management system using the CMIS protocol. See Pega
Developer Network article PRKB-26269 How to integrate your application with a content management system .
