You are an AI assistant tasked with analyzing a passage of text to insert retrieval tokens and identify Prefix-intent (PI) and Key Factual Information (KFI). A Prefix-Intent (PI) should be a piece of text that should precede factual information, it must not be only 1 or 2 words. Key Factual Information (KFI) should be meaningful and include important details.

Your goal is to insert a  <|retrieval|> token after it is clear what the intent of the text is (e.g., "The president of the USA is"), but  before the key factual information is stated (e.g., "Joe Biden"). Whenever there is a <|retrieval|> token, we will retrieve the key factual information.

Here is the passage you will be working with:

<passage>
Karl Erb Karl Erb (13 July 1877 – 13 July 1958) was a German tenor vocalist who made his career first in opera and then in oratorio and lieder recital. He excelled in all these genres, and before 1920 gave classic performances of key roles in modern works, and created lead roles in those of Hans Pfitzner. He was the first husband of Maria Ivogün and was considered by many the ideal Evangelist in the St Matthew Passion of Johann Sebastian Bach. Origins and early training Erb was born in Ravensburg. As a child, he was enrolled in the local Liebfrauenkirche charity choir and music class. His mother taught him to love poetry and he excelled at school. His voice did not break abruptly, but deepened and intensified to a beautiful and spiritual timbre. He was sought out for private musical events and performed in amateur theatre at the Ravensburg Konzerthaus. He later worked at Wolfegg and at Rot as cashier for the State Gas and Waterworks. In 1902, the Konigliche Hoftheater in Stuttgart burnt down, and the company worked temporarily in Ravensburg. Erb, assisting the choir in Cavalleria rusticana, was noticed by . Von Putlitz had been appointed Theatre Intendant at Munich long before through the personal efforts of Richard and Cosima Wagner, cf Ernest Newman, and offered a chance to sing solo. He declined, but further offers were made. Stuttgart In 1906, aged 29, he started an unpaid probationary year at Stuttgart (beginning January 1907, which led to a five-year paid contract. He had the help of a young répétiteur, a singing teacher, a drama tutor (Hans Islaub, who got rid of his Swabian accent) and a ballet master. He studied the roles of Max (Der Freischütz), Lionel (Martha), Walter (Die Meistersinger von Nürnberg) and Mathias in Der Evangelimann by Wilhelm Kienzl. Through the singer Elsa Wiborg, he was given the chance to sing privately for the King and Queen; then, on 14 June 1907, he made his debut in Evangelimann at the new Hoftheater. Erb was also gave recitals and made oratorio appearances during his probation at Stuttgart. He then appeared as Lohengrin (in which the shimmering brightness of his voice was especially effective), as Buddha (in Adolf Vogel's Maja ), as Little Massarena in Le domino noir, Achilles (Iphigenia in Aulis), Walter (Meistersinger) and as Faust in the title role of Gounod's opera. By the end of the trial year he had sung at the Hoftheater at 30 evenings or masterclasses: an unparalleled success. Soon afterwards, at von Putlitz's urging, Erb took singing lessons from Felix Decken, a tenorbuffo, who tried to break and rebuild his technique. Erb, deeply undermined, sacked him and nearly broke with von Putlitz, but instead they agreed that he pass the winter season 1908 as leading lyric tenor for the brand new Theatre at Lübeck. Lübeck Erb opened triumphantly (October 1908) in Lohengrin. He maintained a sober existence, but gravitated to the social circle of Ida Boy-Ed, where he mixed with Hermann Abendroth, Wilhelm Furtwängler and others. He travelled to Hamburg to see Caruso and Edith Walker in Tosca. Greatly inspired, he added Lionel (Martha), Manrico (Il trovatore), Gomez (Das Nachtlager in Granada (Kreutzer)), Froh (Das Rheingold), Florestan (Fidelio), Alessandro Stradella in Friedrich von Flotow's opera, the Duke of Mantua (Rigoletto), Turiddu (Cavalleria rusticana), Fenton (Die lustigen Weiber von Windsor (Carl Otto Nicolai)), Hoffmann in Jacques Offenbach's opera, and Alfred in Die Fledermaus to his repertoire. All these parts were sung in German. In April 1909 at the end of his first season in Lübeck, he returned to Stuttgart and showed
</passage>

Follow these steps to complete the task:

1. Inserting retrieval tokens:
   a. Read through the text carefully.
   b. Identify potential Prefix-Intent (PI) sections that consist of a single intent and could serve as a search query. You must not modify the prefix intent and it MUST be part verbatim in the passage. It cannot be single or only a few words.
   c. For each identified PI, evaluate if the following sentence/subsentece that could serve as Key Factual Information (KFI).
   d. Insert <|retrieval|> tokens into the text AFTER the Prefix Intent (PI) and BEFORE key factual information is stated (KFI).
   e. Key Factual information should not intersect with Prefix Intent.

2. Identifying Prefix-Intent (PI) and Key Factual Information (KFI):
   a. For each <|retrieval|> token you've inserted, identify the preceding text as the Prefix-Intent (PI).
   b. Identify the following text, up to the next PI, as the Key Factual Information (KFI).
   c. Ensure that both PI and FI are short subsentences or phrases but not 1 or 2 words.

3. Insert <|start-PI|>,<|end-PI|>, <|start-KFI|>, <|end-KFI|>.
   a. For each identified Prefix Intent (PI), add a start and end special tokens (<|start-PI|>,<|end-PI|>) to quickly identify them.
   b. Do the same for the Key Factual Information (KFI) (<|start-KFI|>, <|end-KFI|>)
   c. Ensure that the very first PI in the passage is preceded by <|start-PI|>.
   d. Double-check that every PI and KFI is properly enclosed in these tags.

4. Describing ideal retrieved information:
   a. Given the Prefix-Intent (PI) and Key Factual Information (KFI), imagine an ideal retriever and enormous corpus. 
   b. Using the retriever and corpus, imagine that you can retrieve information given the Prefix-Intent.  
   c. Describe how that content should look like so it helps generating the Key Factual Information (KFI)


5. Reformulate the Prefix Intent if necessary: Reformulate it to not be impersonal. This means that if the subject it is not identified (e.g. it, he, she) you need to add the appropriate subject so the prefix-intent can be understood by itself. The subject should be changed from the previous information in the passage. Reformulated Prefix should not add any extra information or intent that is not mentioned in the original Prefix Intent.


6. Output format:
   For each pair of Prefix-Intent (PI) and Key Factual Information (KFI) you identify, provide the following output separating each example in a JSON list output. Ensure that it is actually a JSON.

   - Prefix_intent: [Write the Prefix Intent here]
   - Prefix_reformulated: [Write the Prefix Intent reformulated]
   - Key_Factual_Information: [Write the Key Factual Information here]
   - Verification: [Confirm that the KFI can be directly derived from the PI given a strictly connected context]
   - Ideal_Knowledge: [Describe how the ideal retrieved content should look to generate the KFI]
   - Explanation: [Briefly explain how the PI and KFI connect and why you chose to insert the <|retrieval|> token in that position]


7. Final step:
   After you have completed the analysis and provided outputs for all identified PI-KFI pairs, present the original passage with the <|retrieval|> tokens inserted in their appropriate positions

Here's an example of the expected output format:

Passage: Girmal Falls General This waterfall extends to a height of up to 100 feet, making it the highest waterfall of Gujarat. The picturesque beauty of this site makes it popular among visitors and people of the region alike. The water swiftly falls from a great height, creating a fog like condition that’s eye catching. The government of this state is working on many projects to make this place an ideal picnic spot and a tourist attraction. The fall comes to its best form at the time of monsoon and provides an immensely striking appearance. Some of the best natural features of Gujarat can be explored in this place. This place is a nice and refreshing retreat for any traveler.

```json
{ "results" : [
  {
    "Prefix_intent": "Girmal Falls General This waterfall extends to a height of up to",
    "Prefix_reformulated": "What is the height of Girmal Falls?",
    "Key_Factual_Information": "100 feet, making it the highest waterfall of Gujarat",
    "Verification": "The KFI directly provides the height information requested in the PI.",
    "Ideal_Knowledge": "A list of waterfalls in Gujarat, India, with their heights and rankings, specifically mentioning Girmal Falls as the highest at 100 feet.",
    "Explanation": "The PI introduces Girmal Falls and sets up a query about its height, while the KFI provides the specific measurement and its significance. The <|retrieval|> token is inserted to indicate where additional information might be needed to support the factual statement."
  },
  {
    "Prefix_intent": "The water swiftly falls from a great height, creating",
    "Prefix_reformulated": "What does the water falling from Girmal Falls create?",
    "Key_Factual_Information": "a fog like condition that's eye catching",
    "Verification": "The KFI directly describes the effect created by the falling water, as prompted by the PI.",
    "Ideal_Knowledge": "Detailed descriptions of the visual effects created by high waterfalls, including the formation of mist or fog-like conditions due to water droplets in the air.",
    "Explanation": "The PI describes the water falling and sets up a query about its effect, while the KFI provides the specific visual phenomenon created. The <|retrieval|> token is inserted to indicate where additional information might be needed to support the description."
  },
  {
    "Prefix_intent": "The fall comes to its best form at the time of",
    "Prefix_reformulated": "When does Girmal Falls come to its best form?",
    "Key_Factual_Information": "monsoon and provides an immensely striking appearance",
    "Verification": "The KFI directly answers when the waterfall is at its best and describes its appearance, as prompted by the PI.",
    "Ideal_Knowledge": "Information on the seasonal variations of Girmal Falls, highlighting the monsoon season's impact on water flow and visual appeal.",
    "Explanation": "The PI sets up a query about the best time to view the falls, and the KFI provides the specific season and describes the appearance. The <|retrieval|> token is inserted to indicate where additional information about seasonal changes might be needed."
  }],
"Updated_Passage":"<|start-PI|> Girmal Falls General This waterfall extends to a height of up to <|end-PI|> <|retrieval|> <|start-KFI|> 100 feet, making it the highest waterfall of Gujarat <|end-KFI|>. The picturesque beauty of this site makes it popular among visitors and people of the region alike. <|start-PI|> The water swiftly falls from a great height, creating <|end-PI|> <|retrieval|> <|start-KFI|> a fog like condition that’s eye catching <|end-KFI|>. The government of this state is working on many projects to make this place an ideal picnic spot and a tourist attraction. <|start-PI|> The fall comes to its best form at the time of <|end-PI|> <|retrieval|> <|start-KFI|> monsoon and provides an immensely striking appearance <|end-KFI|>. Some of the best natural features of Gujarat can be explored in this place. This place is a nice and refreshing retreat for any traveler."
}

```
8. Final check:
  a. Review the Updated_Passage to ensure all PIs and KFIs are properly tagged.
  b. Verify that the first PI in the passage starts with <|start-PI|>.
  c. Make sure there are no missing or misplaced tags.
 
Remember to analyze the entire passage, identify all relevant PI-KFI pairs, and provide the output for each pair as specified. After completing the analysis, present the original passage with the <|retrieval|> tokens inserted in their appropriate positions as part of a new key in the JSON file. Only Ouput the JSON File.