About applying multiple signatures to formsAdded by IBM on August 8, 2013 | Version 1 (Original)
|Documents often require multiple signatures. Furthermore, it is common practice for some signatures to endorse other signatures. XFDL provides a signature filtering system to support multiple signatures in a single document.
Multiple signatures allow any combination of form elements to be included or excluded from a signature, which in turn allows forms to be divided into logical sections for the purposes of signing.
For example, an insurance claim requires the claimant to sign the document. Later, the insurance adjuster may also have to sign the document, both to endorse the information provided by the claimant and to endorse information they have added to the claim.
XFDL includes a series of signature filters that are implemented as XFDL options. The complete list of available signature filters is:
Each filter applies to a different cross-section of XFDL elements. For example, the signitems and signitemrefs filters control which items are signed or ignored, while the signoptions and signoptionrefs filters control which options are signed or ignored. Each level of filter also has an assigned order of precedence. For example, filters at the option level override filters at the item level. The order of precedence for these filters is outlined in Order of precedence of filters.
By using these filters in combination, XFDL provides complete control over which elements are omitted from a signature (or alternately to indicate which elements should be included in a signature, though 'inclusive logic' filters should be used sparingly and with great care).
The signatures will sign separate portions of the form, or will overlap with other signatures, as specified by the filters used. For example, the first signature may use a set of filters that includes all elements in the first half of a page. The second signature may use a filter that includes the first signature and the first half of the page. Finally, a third signature might use a filter that includes the entire page and both the first and second signatures.
For example, a document may include a "For Office Use Only" section that should not be signed by the original user. By applying the correct filters, this section can be excluded from the signature, allowing office workers to complete those portions of the document even after the document has been signed.