代码大神求教，代码中的符号#、@都是什么意思

<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>
在上面的代码中，#、@都什么意思，还有<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" />中的ge、le都是什么意思