I have a question about the Real-time Clock component (RTC) for the x86 VMM found here:

import <RTC.idl4>;

import <PutChar.idl4>;

component CMOS {

    hardware;

    provides IOPort cmos_address;

    provides IOPort cmos_data;

    attribute string cmos_address_attributes = "0x70:0x70";

    attribute string cmos_data_attributes = "0x71:0x71";

}

component RTC {

    provides RTC rtc;

    maybe uses PutChar putchar;

    uses IOPort cmos_address;

    uses IOPort cmos_data;

    attribute int heap_size = 0;

    /* Connect the hardware RTC to the RTC component */

    composition {

        component CMOS cmos;

        connection seL4HardwareIOPort rtc_cmos_address(from cmos_address, to cmos.cmos_address);

        connection seL4HardwareIOPort rtc_cmos_data(from cmos_data, to cmos.cmos_data);

    }

    configuration {

        cmos.cmos_address_attributes <- cmos_address_attributes;

        cmos.cmos_data_attributes <- cmos_data_attributes;

    }

}

What is the meaning of the last two statements in the configuration block? what is the scoping rules for the "cmos_address_attributes" and "cmos_data_attributes" variables? It looks like these attributes are already set in the definition of the CMOS component? They seemed to be assigned again in the configuration block?