A method for expanding an answer key to verify a question and answer system is provided in the illustrative embodiments. A definition is constructed of an extended answer type. The extended answer type represents an answer type of an unrepresented answer. The unrepresented answer is unrepresented in the answer key as a valid response to a question in a set of valid responses to the question in the answer key. The extended answer type is created in the answer key according to the definition. The extended answer type is populated such that the unrepresented answer becomes as additional valid response to the question, the creating and the populating extending the answer key to form an extended answer key. The populated extended answer type in the extended answer key is used to verify that a generated answer from the Q and A system is correct.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A method for expanding an answer key to verify a question and answer (Q and A) system, the method comprising: constructing a definition of an extended answer type, wherein the extended answer type represents an answer type of an unrepresented answer, wherein the unrepresented answer is unrepresented in the answer key as a valid response to a question in a set of valid responses to the question in the answer key; creating, using a processor and a memory, the extended answer type in the answer key according to the definition; populating the extended answer type such that the unrepresented answer becomes as additional valid response to the question, the creating and the populating extending the answer key to form an extended answer key; and using the populated extended answer type in the extended answer key to verify that a generated answer from the Q and A system is correct. 2. The method of claim 1, wherein the generated answer is incorrect according to an existing answer type in the answer key. 3. The method of claim 1, further comprising: forming the definition by modifying an abstract definition; constructing a second definition of a second extended answer type, wherein the second extended answer type represents an answer type of a second unrepresented answer. 4. The method of claim 3, wherein the abstract definition is used as a placeholder in the extended answer key for a third extended answer type. 5. The method of claim 1, wherein the unrepresented answer becomes the additional valid answer because a computation using the populated extended answer type results in the additional valid response. 6. The method of claim 1, wherein the unrepresented answer becomes the additional valid answer because a logic described in a metadata of the extended answer key computes to make the unrepresented answer the additional valid response. 7. The method of claim 1, wherein the unrepresented answer becomes the additional valid answer by being a member of a range of values specified in the populated extended answer type. 8. The method of claim 1, wherein the unrepresented answer becomes the additional valid answer by being a member of a range of values, wherein the range of values is computed using logic in a metadata of the extended answer key. 9. The method of claim 1, further comprising: configuring the extended answer type with a changeable condition, wherein a value of the additional valid answer changes when the condition changes. 10. The method of claim 1, wherein the extended answer key in an Extensible Markup Language (XML) document, wherein the definition is an XML structure. 11. The method of claim 1, wherein the question comprise a sentence in natural language, wherein the Q and A system is configured to respond to the natural language question. 12. The method of claim 1, wherein the question comprise a sentence in natural language, wherein the Q and A system is configured to respond to the natural language question using another extended answer type to represent answers one of (i) based on a cultural reference, (ii) in a particular language, and (iii) from a set of synonyms.