Firstly comes exploration of the origin and evolvement of pre-emption, with some words devoted to the future tendency of pre-emption 首先，对优先购买权的起源和发展进行了考察，描述了该权利在不同历史时期的发展与变化以及未来的走向。
After that, some discussions are made on the condition, period, method, efficiency of the performance of pre-emption and concurrency of pre-emption 第五，讨论了优先购买权的行使条件、行使期限、行使方式、行使效力和优先购买权的竞合等问题。
After that, some discussions are made on the condition, period, method, efficiency of the performance of pre-emption and concurrency of pre-emption 第五，讨论了优先购买权的行使条件、行使期限、行使方式、行使效力和优先购买权的竞合等问题。
Pre-emption refers to the privilege granted by law or contract to purchase the object in advance of the third party of same conditions 优先购买权是指特定人依照法律规定或者合同约定而享有的在出卖人出卖其标的物给第三人时，得以同等条件优先于他人而购买的权利。
Under the pre-emption doctrine, touted by the bush administration, an enemy that is in the process of acquiring weapons of mass destruction can be attacked before using those weapons 布什政府声称，根据预防性原则，拥有大规模杀伤武器的敌人在使用这些武器前就可以被攻击。
Consequently, the theory of conditionally formed rights, the theory-of claim or creditor's rights have all been proved to be void . the fourth part concerns the scope and types of pre-emption 附条件形成权说、请求权说、物权说或债权说在理论上都不成立。第四，对优先购买权的类型及其适用范围进行了探讨。
Each of the common owners shall enjoy the rights and assume the obligations respecting the joint property . each co-owner by shares shall have the right to withdraw his own share of the joint property or transfer its ownership . however, when he offers to sell his share, the other co-owners shall have a right of pre-emption if all other conditions are equal 新颖性，是指在申请日以前没有同样的发明或者实用新型在国内外出版物上公开发表过在国内公开使用过或者以其他方式为公众所知，也没有同样的发明或者实用新型由他人向专利局提出过申请并且记载在申请日以后公布的专利申请文件中。
However, house tenant's pre-emptive right in housing reform shall be stipulated as statutory pre-emptive right, for it is the same as tenant's pre-emptive right . pre-emption right should be acquired in law-stipulated legal relations, the moment the basic legal relations form, and must not be solely transferred 只有其中原住户的优先购买权，由于实质上是承租人优先购买权而应确认为法定优先购买权；优先购买权应在法定范围内取得、基础关系成立时取得、不能单独转让而取得。
Thirdly, through analyzing and commenting some classical theories of pre-emption, the author draws the conclusion that pre-eruption is a right in expectancy and a formed right; statutory pre-emption is of the power of real rights, while the contractual pre-emption is of the power of creditor's rights with exception that it is of the power of real rights by public summons 第三，通过对优先购买权法律性质的几种典型学说逐个评析，得出优先购买权是一种期待权、形成权；法定优先购买权具有物权效力，约定优先购买权只要具备法定公示方式者，才可以认定具有物权效力，否则只具有债权效力。
Thirdly, through analyzing and commenting some classical theories of pre-emption, the author draws the conclusion that pre-eruption is a right in expectancy and a formed right; statutory pre-emption is of the power of real rights, while the contractual pre-emption is of the power of creditor's rights with exception that it is of the power of real rights by public summons 第三，通过对优先购买权法律性质的几种典型学说逐个评析，得出优先购买权是一种期待权、形成权；法定优先购买权具有物权效力，约定优先购买权只要具备法定公示方式者，才可以认定具有物权效力，否则只具有债权效力。
