Some properties are required, some are optional. Some have simple string values, some are complex resources.
一些属性是必要的，一些则是可选的。一些只是简单的字符串值，一些则是复杂的资源。
In the new curriculum, some courses are compulsory, while others are optional for middle school students.
在新课程中，一些课程是必修课，而另一些是中学生的选修课。
In this process, some of the variables are primary elements that are necessary for input, while others are optional.
在这一过程中，一些变量是基本的元素，是必须输入的，而其它一些却是可选的。
Some courses in college are required while others are optional.
大学里有的课程是必修的,有是是选修的.
Some courses in college are required while others are optional.
大学里有的课程是必修的，有是是选修的。
In addition, in some programs some structures are optional.
此外，在某些程序中有一部分结构是可选的。
Recall from the discussion of Figure 2 in the first article that the sub-fields of req-body are (omitting some of the optional fields).
回想在第一篇文章图2的讨论中，req - body的子字段有(去掉了一些可选字段)。
A service specification is a set of three specification elements, all equally important; though, in some cases, they are optional in a model depending on the type of service being modeled.
服务规范有三个规范要素，所有都同样重要，虽然在某种情况下，根据服务的建模类型可对它们进行选择。
If for marketing purpose or for some other reasons where optional fields are needed, we suggest to mark optional fields clearly instead of indicating the mandatory fields.
如果出于市场调查或其他一些理由需要放一些选填内容，我们建议清晰地标注这些问题，而不是把必填内容标注出来。
Optional features are requirements that are present in some members of the product line, and alternative features are requirements that some members of the product line choose from.
可选功能是产品线的部分成员中存在的需求，替代功能是产品线的部分成员从中进行选择的需求。
There also are plenty of optional safety equipments that you can get if you want some extra safety in the car.
如欲使爱车更加安全，另有大量的选装安全装备可供选择。
To simplify serialization, we'll make sure all objects are directly or indirectly contained by Forum. Some other useful optional attributes include.
为了简化序列化的过程，我们要保证所有的对象都是直接或者间接包含在Forum中的。
As is the case with Struts, there are several add-ons (often called optional Shale components in the Shale world) that have some dependencies of their own.
和Struts一样，Shale还有一些附件(在Shale中常被称作可选Shale组件)，这些附件各自又有其依赖项。
Some optional items that I found useful are as follows.
一些可选项目，我发现有用的内容如下。
The number increases with each version of Oracle, some of them are mandatory, others are optional.
它们的数量随着版本的升级而增加，其中一些是强制性运行的，而另一些则是可选的。
Implementing a custom code access permission involves the following steps, some of which are optional.
实现自定义代码访问权限包括下列步骤，其中的一些步骤是可选的。
In therory the amount of tips is optional, but in many places of Ameica, there are some unwritten rules on tipping.
理论上小费给多少纯属自愿，但是在美国，不少地方都有不成文的规矩。
I need to generate a secret key (or password) with agreement of multiple parties out of which some parties are optional.
我需要生成一个密钥(或密码)与多个当事人双方的协议是可选的。
Compulsive plus optional courses are good to train talents with multiple skills, but, as to the new teaching mode, there are some shortcomings.
主辅修教学有利于复合型人才的培养，但作为一种新的教学模式仍存在某些弊病。
Some things shouldn't be optional - and for too many of us, they are. For example; intelligent eating, structured and regular exercise and healthy lifestyle.
有些东西是强制性的，但更多的东西并不是，比如科学饮食，坚持、系统地锻炼，保持健康等等。
There are also some optional textbooks and recommended Web material. And there will be some additional material handed out in class.
另外还有一些推荐的教材和网上资料，在课堂上还会分发一些补充材料。
Through the analysis of the present teaching situation of physical education based on "the optional subjects" in the universities of China, some shortcomings and incompetence are found.
通过对我国高校“选项课”体育教学现状进行分析，发现它仍有不少欠缺和不完善的地方。
Through the analysis of the present teaching situation of physical education based on "the optional subjects" in the universities of China, some shortcomings and incompetence are found.
通过对我国高校“选项课”体育教学现状进行分析，发现它仍有不少欠缺和不完善的地方。
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