The Washington state Constitution requires that all taxes be uniform upon the same class of property within the territorial limits of the authority levying the tax. In order to comply with this constitutional mandate and ensure that all taxes are uniform, all real property must be valued in a manner consistent with this principle of uniformity. Also, to comply with statutory and case law, the county assessor must value all taxable real property in the county on a regular, systematic, and continuous basis. All taxable real property within a county must be valued or revalued annually, and each county assessor must review all taxable real property characteristics in accordance with the International Association of Assessing Officers' standards for physical inspections. All taxable real property within a county must also be physically inspected at least once every six years, per RCW 84.41.030. The assessor must adhere to a revaluation plan that will ensure equality and uniformity in the valuation of real property, and must use proper appraisal methods. The administrative rules in this chapter describe and explain the processes to be used by the county assessor in valuing and revaluing real property for purposes of taxation.