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>
China Railway DF4 The DF4 (Chinese: 东风4) is a type of diesel-electric locomotive used in the People's Republic of China. It has been in production since 1969 and is still produced as of 2007 by several local companies. It is the most common locomotive in China and is used for both passenger and freight services. Models DF4 The first DF4 was built in 1969 in Dalian. The first 108 locomotives that were built here are the original DF4s using the 16V240ZJ engine. It took seven years to build all 108 locomotives of this type. Due to unstable technique in the production of early-built DF4 locomotives, malfunctions of mechanic and electric parts occurred frequently during the operation, especially the diesel engine. Thus, most DF4 locomotives were taken out of service for maintenance, and railroad engineers from Fengtai Locomotive Depot sarcastically joked that the DF4 "can't make it from Dongdan to Xisi". Therefore, Dalian Locomotive Works introduced 16V240ZJA, an improved diesel engine. They are nicknamed "Watermelon". Few of the first series DF4 are still in operation, however the first ever is a permanent exhibition at the Beijing Railway Museum. DF4A The DF4A distinguishes itself from first series DF4s with an improved engine, the 16V240ZJA. Production started in 1976 (the first model being DF4-0109) and lasted until 1984. The DF4A designation is unofficial. DF4B Nicknamed Watermelon, Military Police, or Orange. General speaking, Watermelons and Militarys are used for freight, while Oranges are almost used for passenger services. DF4B are very similar to standard DF4, apart from an improved engine (16V240ZJB). Production started in Dalian in 1984. DF4C The DF4C was supposed to replace the DF4B as the main diesel locomotive in China and comes with several improvements, including a new engine revision (16240ZJC). The first DF4C was produced in 1985 and batch production started four years later, in 1989, and lasted until roughly the end of the 20th century. The DF4C comes in a different color scheme than the previous DF4s, namely dark blue and later light blue and beige. The passenger version, informally called DF4CK, has an A1A-A1A wheel arrangement. Gearing variations The DF4, DF4B and DF4C were each produced with two different gear ratios, "passenger" (up to or for DF4C) and "freight" (up to ). The passenger variant was often painted orange. DF4D The DF4D, the most recent DF4 revision, has been produced since 1996 with the 16V240ZJD engine. The passenger versions increased top speed to or . The freight version comes in a different color scheme than the previous DF4Ds, namely green (7000 Series) and later light blue (4000 Series) and yellow. The green version sat on radial bogies but later converted to standard bogies. Their top speed to 100 km/h (62 mph). DF4DJ The DF4DJ, originally DF4DAC, of which only 2 were built had AC drive technology supplied by Siemens. They were China's first AC drive diesel locomotive.<ref>DF4DJ 'baike.baidu.com</ref> DF4DD A road-switcher version of the DF4 with side walkways and a full-body cab similar to modern American locomotives. It was the most powerful road switcher class in China until the introduction of the HXN3B and HXN5B classes. DF4E The DF4E is a 2 unit locomotive of total power 4.86MW (2x2.43MW) Manufacturers DF4s have been manufactured by several companies: CSR Sifang Locomotive and Rolling Stock Co., Ltd. CSR Ziyang Locomotive Works (DF4B, DF4C & DF4C (A1A)) Dalian Locomotive & Rolling Stock Works Datong locomotive factory North Korea In 2001, the Korean State Railway bought two locomotives of type CKD4A (DF4D) new from CNR Dalian; these were delivered in July 2002. These are powered by the same 16V240ZJD as the Chinese
</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.