The above message (formatted for readability) may be signed for additional security. In practice, all the data contained in a <samlp:AuthnRequest> , such as Issuer which contains the SP ID, and NameIDPolicy , has been agreed between IdP and SP beforehand (via manual information exchange or via SAML metadata ). In that case signing the request is not a security constraint. When the <samlp:AuthnRequest> contains information not known by the IdP beforehand, such as Assertion Consumer Service URL, signing the request is recommended for security purposes.
Susan Lafond, a Nationally Board Certified Teacher in English as a New Language (EAYA ENL), has 20 years of combined experience teaching ESL and foreign language. She currently works as a professional development assistant for educators with New York State United Teachers (NYSUT). She serves on AFT's ELL Educator Cadre, as well as an expert practitioner and advisor to Colorín Colorado, developing and editing materials for the web site. Her success with high school students was featured on the site in their From the Heart section. She participated in a webcast for them that focused on supporting ELLs in content classes. In 2006, she traveled to Beirut, Lebanon as a turnkey teacher trainer for the Lebanese Syndicate on behalf of AFT.
In contrast, human language is open-ended and productive , meaning that it allows humans to produce a vast range of utterances from a finite set of elements, and to create new words and sentences. This is possible because human language is based on a dual code, in which a finite number of elements which are meaningless in themselves (. sounds, letters or gestures) can be combined to form an infinite number of larger units of meaning (words and sentences).  However, one study has demonstrated that an Australian bird, the chestnut-crowned babbler, is capable of using the same acoustic elements in different arrangements to create two functionally distinct vocalizations.  Additionally, pied babblers have demonstrated the ability to generate two functionally distinct vocalisations composed of the same sound type, which can only be distinguished by the number of repeated elements.