xml代码中#、@、%都什么意思

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<?xml version="1.0" encoding="utf-8"?> <Clock version="1" type="awesome" frameRate="30" screenWidth="1080" scaleByDensity="false"> <VariableBinders> <ContentProviderBinder name="weather" uri="content://weather/weather" columns="city_name,temperature,weather_type" countName="hasweather" denpendency="selected_city"> <Variable name="weather_city" type="string" column="city_name" /> <Variable name="weather_temperature" type="int" column="temperature" /> <Variable name="weather_id" type="int" column="weather_type" /> </ContentProviderBinder> </VariableBinders> <ContentProviderBinder name="weather_aqi" dependency="weather" uriFormat="content://weatherinfo/aqi/%s" uriParas="@city_id" columns="aqi,pm25,pm10,so2,no2,pub_time,src,spot" countName="hasweatherinfo"> <Variable name="aqi" type="int" column="aqi" /> <Variable name="pm25" type="int" column="pm25" /> <Variable name="pm10" type="int" column="pm10" /> <Variable name="so2" type="int" column="so2" /> <Variable name="no2" type="int" column="no2" /> </ContentProviderBinder> <!-- 空气质量指数 --> <ContentProviderBinder name="weather_aqi" dependency="weather" uriFormat="content://weatherinfo/aqi/%s" uriParas="@city_id" columns="aqi,pm25,pm10,so2,no2,pub_time,src,spot" countName="hasweatherinfo"> <Variable name="aqi" type="int" column="aqi" /> <Variable name="pm25" type="int" column="pm25" /> <Variable name="pm1" type="int" column="pm25" row="1" /> <Variable name="pm2" type="int" column="pm25" row="2" /> <Variable name="pm3" type="int" column="pm25" row="3" /> <Variable name="pm10" type="int" column="pm10" /> <Variable name="so2" type="int" column="so2" /> <Variable name="no2" type="int" column="no2" /> </ContentProviderBinder> <Var name="air_quality" expression="ifelse(ge(#aqi,0)*lt(#aqi,50),'优',ge(#aqi,50)*lt(#aqi,100),'良',ge(#aqi,100)*lt(#aqi,150),'轻度污染',ge(#aqi,150)*lt(#aqi,200),'中度污染',ge(#aqi,200)*lt(#aqi,300),'重度污染',ge(#aqi,300)*le(#aqi,500),'严重污染','获取信息异常')" type="string" /> <VarArray type="string"> <Vars> <Var name="weather_description" index="#weather_id" /> </Vars> <Items> <Item expression="@wd00" /> <Item expression="@wd01" /> <Item expression="@wd02" /> <Item expression="@wd03" /> <Item expression="@wd04" /> <Item expression="@wd05" /> <Item expression="@wd06" /> <Item expression="@wd07" /> <Item expression="@wd08" /> <Item expression="@wd09" /> <Item expression="@wd10" /> <Item expression="@wd11" /> <Item expression="@wd12" /> <Item expression="@wd13" /> <Item expression="@wd14" /> <Item expression="@wd15" /> <Item expression="@wd16" /> <Item expression="@wd17" /> <Item expression="@wd18" /> <Item expression="@wd19" /> <Item expression="@wd20" /> <Item expression="@wd21" /> <Item expression="@wd22" /> <Item expression="@wd23" /> <Item expression="@wd24" /> </Items> </VarArray> 代码大神，请教一下，以上的代码中#、@、%都什么意思，还有ge(#aqi,0)和*le是什么意思