...The Distinguished Encoding Rules, or DER, of the ASN.1 standard follows this approach but includes numerous constraints and, more importantly, demands that data fields to be described using binary metadata rather than text. The Secure Protocol Format, or SPF, was created as a simplified version of DER. In addition to delimiting data by length, it also affords programmers the ability to use text for describing data, just like tags are used in HTML and XML. Thus, SPF provides a simple and practical approach to preventing command injection attacks while allowing text to describe data.