```xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns4:query_definition xmlns:ns2="http://www.i2b2.org/xsd/cell/crc/psm/1.1/" xmlns:ns4="http://www.i2b2.org/xsd/cell/crc/psm/querydefinition/1.1/" xmlns:ns3="http://www.i2b2.org/xsd/cell/crc/psm/analysisdefinition/1.1/">
    <query_name>(t) AsthmaAsthmaAsthma@20:19:01</query_name>
    <query_timing>ANY</query_timing>
    <specificity_scale>0</specificity_scale>
    <panel>
        <panel_number>1</panel_number>
        <panel_timing>ANY</panel_timing>
        <panel_accuracy_scale>100</panel_accuracy_scale>
        <invert>0</invert>
        <total_item_occurrences>1</total_item_occurrences>
        <item>
            <hlevel>3</hlevel>
            <item_name>Asthma</item_name>
            <item_key>\\ICD10_ICD9\Diagnoses\(J00-J99) Dise~45pn\(J40-J47) Chro~fbox\(J45) Asthma\</item_key>
            <item_icon>FA</item_icon>
            <tooltip>Diagnoses \ Diseases of the respiratory system (j00-j99) \ Chronic lower respiratory diseases (j40-j47) \ Asthma</tooltip>
            <class>ENC</class>
            <item_is_synonym>true</item_is_synonym>
        </item>
    </panel>
    <subquery_constraint>
        <first_query>
            <query_id>Observation A</query_id>
            <join_column>STARTDATE</join_column>
            <aggregate_operator>FIRST</aggregate_operator>
        </first_query>
        <operator>LESS</operator>
        <second_query>
            <query_id>Observation B</query_id>
            <join_column>STARTDATE</join_column>
            <aggregate_operator>LAST</aggregate_operator>
        </second_query>
        <span>
            <operator>GREATEREQUAL</operator>
            <span_value>2000</span_value>
            <units>DAY</units>
        </span>
    </subquery_constraint>
    <subquery>
        <query_id>Observation A</query_id>
        <query_type>EVENT</query_type>
        <query_name>Observation A</query_name>
        <query_timing>SAMEINSTANCENUM</query_timing>
        <specificity_scale>0</specificity_scale>
        <panel>
            <panel_number>0</panel_number>
            <panel_timing>SAMEINSTANCENUM</panel_timing>
            <panel_accuracy_scale>100</panel_accuracy_scale>
            <invert>0</invert>
            <total_item_occurrences>1</total_item_occurrences>
            <item>
                <hlevel>3</hlevel>
                <item_name>Asthma</item_name>
                <item_key>\\ICD10_ICD9\Diagnoses\(J00-J99) Dise~45pn\(J40-J47) Chro~fbox\(J45) Asthma\</item_key>
                <item_icon>FA</item_icon>
                <tooltip>Diagnoses \ Diseases of the respiratory system (j00-j99) \ Chronic lower respiratory diseases (j40-j47) \ Asthma</tooltip>
                <class>ENC</class>
                <item_is_synonym>true</item_is_synonym>
            </item>
        </panel>
    </subquery>
    <subquery>
        <query_id>Observation B</query_id>
        <query_type>EVENT</query_type>
        <query_name>Observation B</query_name>
        <query_timing>SAMEINSTANCENUM</query_timing>
        <specificity_scale>0</specificity_scale>
        <panel>
            <panel_number>0</panel_number>
            <panel_timing>SAMEINSTANCENUM</panel_timing>
            <panel_accuracy_scale>100</panel_accuracy_scale>
            <invert>0</invert>
            <total_item_occurrences>1</total_item_occurrences>
            <item>
                <hlevel>3</hlevel>
                <item_name>Asthma</item_name>
                <item_key>\\ICD10_ICD9\Diagnoses\(J00-J99) Dise~45pn\(J40-J47) Chro~fbox\(J45) Asthma\</item_key>
                <item_icon>FA</item_icon>
                <tooltip>Diagnoses \ Diseases of the respiratory system (j00-j99) \ Chronic lower respiratory diseases (j40-j47) \ Asthma</tooltip>
                <class>ENC</class>
                <item_is_synonym>true</item_is_synonym>
            </item>
        </panel>
    </subquery>
</ns4:query_definition>

```

I want to find patients who have been diagnosed with asthma (ICD-9 code: 493) within 20 days of the start date of the observation window, with a specificity scale of 0, and a panel accuracy scale of 100, using the panel named "AsthmaAsthmaAsthma@20:19:01" with a subquery constraint that checks if the first query's start date is less than or equal to 20 days from the second query's last date, using the same instance number for both subqueries.