精华内容
下载资源
问答
  • Data model - 数据模型

    2019-09-03 19:06:05
    Data model - 数据模型 ...https://docs.python.org/3/reference/datamodel.html 数据模型 https://docs.python.org/zh-cn/3/reference/datamodel.html 1. numbers.Number These are created by numeric literals an...

    Data model - 数据模型

    Data model
    https://docs.python.org/3/reference/datamodel.html

    数据模型
    https://docs.python.org/zh-cn/3/reference/datamodel.html

    1. numbers.Number

    These are created by numeric literals and returned as results by arithmetic operators and arithmetic built-in functions. Numeric objects are immutable; once created their value never changes. Python numbers are of course strongly related to mathematical numbers, but subject to the limitations of numerical representation in computers.
    此类对象由数字字面值创建,并会被作为算术运算符和算术内置函数的返回结果。数字对象是不可变的,一旦创建其值就不再改变。Python 中的数字当然非常类似数学中的数字,但也受限于计算机中的数字表示方法。

    literal ['lɪt(ə)r(ə)l]:adj. 文字的,逐字的,无夸张的
    

    Python distinguishes between integers, floating point numbers, and complex numbers:
    Python 区分整型数、浮点型数和复数:

    1.1 numbers.Integral

    These represent elements from the mathematical set of integers (positive and negative).
    此类对象表示数学中整数集合的成员 (包括正数和负数)。

    There are two types of integers:
    整型数可细分为两种类型:

    1.1.1 Integers (int)

    These represent numbers in an unlimited range, subject to available (virtual) memory only. For the purpose of shift and mask operations, a binary representation is assumed, and negative numbers are represented in a variant of 2’s complement which gives the illusion of an infinite string of sign bits extending to the left.
    此类对象表示任意大小的数字,仅受限于可用的内存 (包括虚拟内存)。在变换和掩码运算中会以二进制表示,负数会以 2 的补码表示,看起来像是符号位向左延伸补满空位。

    1.1.2 Booleans (bool)

    These represent the truth values False and True. The two objects representing the values False and True are the only Boolean objects. The Boolean type is a subtype of the integer type, and Boolean values behave like the values 0 and 1, respectively, in almost all contexts, the exception being that when converted to a string, the strings “False” or “True” are returned, respectively.
    此类对象表示逻辑值 False 和 True。代表 False 和 True 值的两个对象是唯二的布尔对象。布尔类型是整型的子类型,两个布尔值在各种场合的行为分别类似于数值 0 和 1,例外情况只有在转换为字符串时分别返回字符串 False 或 True。

    The rules for integer representation are intended to give the most meaningful interpretation of shift and mask operations involving negative integers.
    整型数表示规则的目的是在涉及负整型数的变换和掩码运算时提供最为合理的解释。

    1.2 numbers.Real (float)

    These represent machine-level double precision floating point numbers. You are at the mercy of the underlying machine architecture (and C or Java implementation) for the accepted range and handling of overflow. Python does not support single-precision floating point numbers; the savings in processor and memory usage that are usually the reason for using these are dwarfed by the overhead of using objects in Python, so there is no reason to complicate the language with two kinds of floating point numbers.
    此类对象表示机器级的双精度浮点数。其所接受的取值范围和溢出处理将受制于底层的机器架构 (以及 C 或 Java 实现)。Python 不支持单精度浮点数;支持后者通常的理由是节省处理器和内存消耗,但这点节省相对于在 Python 中使用对象的开销来说太过微不足道,因此没有理由包含两种浮点数而令该语言变得复杂。

    1.3 numbers.Complex (complex)

    These represent complex numbers as a pair of machine-level double precision floating point numbers. The same caveats apply as for floating point numbers. The real and imaginary parts of a complex number z can be retrieved through the read-only attributes z.real and z.imag.
    此类对象以一对机器级的双精度浮点数来表示复数值。有关浮点数的附带规则对其同样有效。一个复数值 z 的实部和虚部可通过只读属性 z.real 和 z.imag 来获取。

    mercy ['mɜːsɪ]:n. 仁慈,宽容,怜悯,幸运,善行
    

    2. Numeric Types - int, float, complex

    There are three distinct numeric types: integers, floating point numbers, and complex numbers.
    有三种不同的数字类型:整数、浮点数和复数。

    Python 的数字类型包括 Integral (int、bool)、Real (float) 和 Complex (complex) 类型。

    展开全文
  • DataModel DataModel元素是Peach根元素的一个子元素。 数据模型通过指定其他子元素(如Number,Blob或String)来定义数据块的结构。 Attributes: name - [必须] 友好的DataModel名称在引用模型或调试时很有用...

    DataModel

    DataModel元素是Peach根元素的一个子元素。 数据模型通过指定其他子元素(如Number,Blob或String)来定义数据块的结构。

    Attributes:

    • name - [必须] 友好的DataModel名称在引用模型或调试时很有用。
    • ref - 引用其他的DataModel作为模板(可选)
    • mutable - 数据元素是否可更改(是否应该进行变异)(可选,默认为true)
    • constraint - 指定一个表达式,帮助Peach识别数据元素是否已被正确使用(可选)

    Valid Child Elements:

    • Blob
    • Block
    • Choice
    • Custom
    • Flag
    • Flags
    • Number
    • Padding
    • String
    • XmlAttribute
    • XmlElement
    • Relation
    • Fixup
    • Transformer
    • Placement

    Examples:

    Peach的pit文件中可以指定任意个数的DataModel(至少一个),但是每个DataModel都必须有一个唯一的名字。通过逻辑将复杂的格式分解为更小的模型,这使得DataModel变得更为阅读、调试和重用。

    名为“HelloWorld”的DataModel包含一个String字符串并输出“Hello world!”

    <DataModel name="HelloWorld">
      <String value="Hello world!" />
    </DataModel>

    DataModels可以引用其他DataModel并用ref属性继承它们的子元素。

    <DataModel name="ParentModel">
      <String value="Hello " />
    </DataModel>
    
    <DataModel name="HelloWorldModel" ref="ParentModel" >
      <String value=" world!" />
    </DataModel>

    References (ref attribute)

    当提供reference(ref属性)时,被引用的DataModel的内容将被复制以作为创建新DataModel的基础。 新DataModel中的任何子元素都将覆盖该基础中具有相同名称的元素。 在这个例子中,子DataModel的Customized包含一个名为Key的字符串。 它的值会覆盖父项中的没有值的字符串“Key”。

    <DataModel name="Template">
      <String name="Key" />
      <String value=": " token="true" />
      <String name="Value" />
      <String value="\r\n" token="true" />
    </DataModel>
    
    <DataModel name="Customized" ref="Template">
      <String name="Key" value="Content-Length" />
      <String name="Value">
        <Relation type="size" of="HttpBody" />
      </String>
      <Blob name="HttpBody" />
    </DataModel>

    输出:

    The output of “Template” is ” : \r\n”
    The output of “Customized” is “Content-Length: 100\r\n”

    在解析成DataModel时,Customized看起来就像两个DataModel的组合。

    <DataModel name="Customized" ref="Template">
      <String name="Key" value="Content-Length" />
      <String value=": " token="true" />
      <String name="Value">
        <Relation type="size" of="HttpBody" />
      </String>
      <String value="\r\n" token="true" />
    </DataModel>
    展开全文
  • The Data Model

    2011-12-07 15:45:43
    The Data Model 数据模型 Your app’s data model comprises your data structures and the business logic needed to keep that data in a consistent state. You never want to design your data model in ...
    The Data Model
    数据模型


    Your app’s data model comprises your data structures and the business logic needed to keep that data in a consistent state. You never want to design your data model in total isolation from your app’s user interface; however, the implementation of your data model objects should be separate and not rely on the presence of specific views or view controllers. Keeping your data separate from your user interface makes it easier to implement a universal app—one that can run on both iPad and iPhone—and also makes it easier to reuse portions of your code later.
    数据模型包括数据结构和在一致状态下保持数据的业务逻辑。你不会想要在与用户界面完全隔离的情况下设计数据模型。但是,数据模型对象的实现应该分离并且不依赖于具体视图的显示或者视图控制器。保持你的数据与用户界面分离会使得实现一个通用app更简单些,也使得稍后你重用代码更加方便。


    If you have not yet defined your data model, the iOS frameworks provide help for doing so. The following sections highlight some of the technologies you can use when defining specific types of data models.
    如果你还没有定义你的数据模型,iOS框架提供了帮助。下面的章节提到的技术你可以在定义具体的数据模型类型的时候使用。


    Defining a Custom Data Model
    定义一个用户数据模型


    When defining a custom data model, create custom objects to represent any high-level constructs but take advantage of the system-supplied objects for simpler data types. The Foundation framework provides many objects (most of which are listed in Table 2-2) for managing strings, numbers, and other types of simple data in an object-oriented way. Using these objects is preferable to defining new objects both because it saves time and because many other system routines expect you to use the built-in objects anyway.
    当定义一个用户数据模型的时候,创建用户对象来负责任何高层的结构,但是系统提供的对象对于简单的数据类型更占有优势。基础框架提供了许多对象(大多数列在表2-2中),关于管理字符串,数字和其他类型的简单数据,用面向对象的方法。用这些对象定义新的对象也是可取的,因为它节省了时间,并且因为其他的系统运行时希望你使用内建的对象。
    表 2-2 基础框架中的数据类型
    Stings and text:
    NSSting(NSMuteableString)
    NSAttributedSting
    (NSMutableAttibutedString)
    Strings in iOS are Unicode based. The string classes provide support for creating and manipulating strings in a variety of ways. The attributed string classes support stylized text and are used only in conjunction with Core Text.
    iOS中的字符串是基于Unicode的。字符串类提供了用于创建和操作多种方式的字符串的支持。
    Numbers:
    NSNumber
    NSDecimalNumber
    NSIndexPath
    When you want to store numerical values in a collection, use number objects. The NSNumber class can represent integer, floating-point values, Booleans, and char types. The NSIndexPath class stores a sequence of numbers and is often used to specify multi-layer selections in hierarchical lists.
    当你想在一个collection中存储一些数值变量的时候,使用number对象。NSNumber类能够表示整数,浮点,布尔和字符类型。NSIndexPath类存储一个数组序列并且经常用于指定层次结构列出的多种选择。
    Raw bytes:
    NSData(NSMutableData)
    NSValue
    For times when you need to store raw streams of bytes, use data objects. Data objects are also commonly used to store objects in an archived form. The NSValue class is typically extended (using categories) and used to archive common data types such as points and rectangles.
    当你想要存储一些原始字节流数据的时候,使用data对象。Data对象也经常用于存储归档形式的对象。NSValue类是典型的扩展(使用类别)并且用来归档常用数据类型,比如点和矩形。
    Dates and times:
    NSDate
    NSDateComponents
    Use date objects to store timestamps, calendar dates, and other time-related information.
    使用data对象来存储时间戳,日历数据和其他的时间相关的信息。
    URLs:
    NSURL
    In addition to their traditional use for referring to network resources, URLs in iOS are the preferred way to store paths to files. The NSURL class even provides support for getting and setting file-related attributes.
    除了对网络资源的传统使用,iOS中的URLs是文件存储路径的首选。NSURL类甚至对获取和设置文件相关的属性提供了支持。
    Collections:
    NSArray(NSMutableArray)
    NSDictionary
    (NSMutableDictionary)
    NSIndexSet
    (NSMutableIndexSet)
    NSOrderedSet
    (NSMutableOrderedSet)
    NSSet(NSMutablesSet)
    Use collections to group related objects together in a single place. The Foundation framework provides several different types of collection classes
    使用collections在一个单独的地方来组织相关的对象。基础框架提供了一些不同的collection类的类型。


    In addition to data-related objects, there are some other data types that are commonly used by the iOS frameworks to manage familiar types of data. You are encouraged to use these data types in your own custom objects to represent similar types of data.
    除了数据相关的对象,还有一些其他的数据类型也经常由iOS框架使用来管理相似的数据类型。鼓励在你自己的对象中使用这些类型来表达相似的数据类型。


    NSInteger/NSUInteger—Abstractions for scalar signed and unsigned integers that define the integer size based on the architecture.
    NSInteger/NSUInteger——基于体系结构定义为整型大小,有符号和无符号的整数。
    NSRange—A structure used to define a contiguous portion of a series. For example, you can use ranges to define the selected characters in a string.
    NSRangs——一个结构,用来定义一系列的连续的部分。比如你可以使用ranges来定义一个字符串中选中的字符。
    NSTimeInterval—The number of seconds (whole and partial) in a given time interval.
    NSTimeInterVal——秒的数值(整体和部分)在一个给出的time interval中。
    CGPoint—An x and y coordinate value that defines a location.
    CGPoint——定义一个位置用的x,y坐标值。
    CGSize—Coordinate values that define a set of horizontal and vertical extents.
    CGSize——定义长宽集合的坐标值
    CGRect—Coordinate values that define a rectangular region.
    CGRect——定义矩形区域的坐标值


    Of course, when defining custom objects, you can always incorporate scalar values directly into your class implementations. In fact, a custom data object can include a mixture of scalar and object types for its member variables. Listing 2-1 shows a sample class definition for a collection of pictures. The class in this instance contains an array of images and a list of the indexes into that array representing the selected items. The class also contains a string for the collection’s title and a scalar Boolean variable indicating whether the collection is currently editable.
    当然了,当定义用户对象的时候,你总可以直接融入标量值到你的类实现中。实际上一个用户数据对象能够包括一个标量和成员值的对象类型的混合。列表2-1显示了一个图像的collection的简单的类定义。实例中的类包含了一个images数组和一个数组的索引列表,表示选择的条目。类也包含了一个collection的标题的字符串和一个标量布尔变量,说明当前的collection是否可以编辑。
    Listing 2-1  Definition of a custom data object
    @interface PictureCollection : NSObject {
       NSMutableOrderedSet* pictures;
       NSMutableIndexSet* selection;
     
       NSString* title;
       BOOL editable;
    }
     
    @property (nonatomic, strong) NSString * title;
    @property (nonatomic, readonly) NSOrderedSet* pictures;
     
    // Method definitions...
     
    @end
    Note: When defining data objects, it is strongly recommended that you declare properties for any member variables that you to expose to clients of the object. Synthesizing these properties in your implementation file automatically creates appropriate accessor methods with the attributes you require. This ensures that object relationships are maintained appropriately and that objects are not released.
    注意:当定义数据对象的时候,它强烈要求你为每一个你暴露给对象的客户的成员变量声明属性。在你的实现文件里综合这些属性自动的为你请求的属性创建属性访问方法。这确保了对象关系被恰当的维护并且对象没有被释放。
    Consider how undo operations on your custom objects might be handled. Supporting undo means being able to reverse changes made to your objects cleanly. If your objects incorporate complex business logic, you need to factor that logic in a way that can be undone easily. Here are some tips for implementing undo support in your custom objects:
    考虑到在你的用户对象上如何取消操作可能会被处理。支持undo意味着能够进行相反的改变,使得用户对象清理干净。如果你的对象有复杂的业务逻辑,你需要让逻辑有一种可以简单undo的方法。这里对于让你的用户对象支持undo操作有一些建议:
    Define the methods you need to make sure that changes to your object are symmetrical. For example, if you define a method to add an item, make sure you have a method for removing an item in a similar way.
    确保你定义的改变对象的方法是对称的。比如,你定义了一个方法来增加一个条目,那么你要保证也存在一个方法是移除一个条目。
    Factor out your business logic from the code you use to change the values of member variables.
    从代码中分解出改变成员变量值的业务逻辑。
    For multistep actions, use the current NSUndoManager object to group the steps together.
    对于多步骤的动作,使用当前的NSUndoManager来把这些步骤组织在一起。
    For more information about how to implement undo support in your app, see Undo Architecture. For more information about the classes of the Foundation framework, see Foundation Framework Reference.
    关于如何在app中实现undo支持参考"Undo Architecture",关于基础框架类的更多信息参考Foundation Framework Reference.


    Defining a Structured Data Model Using Core Data
    使用Core Data定义一个结构化的数据模型
    Core Data is a schema-driven object graph management and persistence framework. Fundamentally, Core Data helps you to save model objects (in the sense of the model-view-controller design pattern) to a file and get them back again. This is similar to archiving (see Archives and Serializations Programming Guide), but Core Data offers much more than that.
    Core Data是一个架构驱动对象图形管理和持久框架。基础的说,Core Data帮助你保存模型对象(类似MCV设计模式)为一个文件,并且取回它们。这类似于归档(参考Archives and Serializations Programming Guide),但是Core Data比那提供了更多。


    Core Data provides an infrastructure for managing all the changes to your model objects. This gives you automatic support for undo and redo, and for maintaining reciprocal relationships between objects.
    Core Data提供了管理你的模型对象所有改变的基础设置。这对undo和redo是自动支持的,并且维护了对象间的相互关系。
    It allows you to keep just a subset of your model objects in memory at any given time, which is very important for iOS apps.
    在给定的任何时间内在内存中允许你保存你的模型对象的一个子集,这在iOS apps中非常重要。
    It uses a schema to describe the model objects. You define the principal features of your model classes—including the relationships between them—in a GUI-based editor. This provides a wealth of basic functionality “for free,” including setting of default values and attribute value validation.
    它使用一个架构来描述模型对象。你定义模型类的主要特性,包括在基于图形界面的编辑器之间的关系。这提供了一个“自由”的丰富的基本功能,包括设置默认。
    It allows you to maintain disjoint sets of edits of your objects. This is useful if you want to, for example, allow the user to make edits in one view that may be discarded without affecting data displayed in another view.
    它允许你维护不相交的集合的编辑对象。当你需要的时候,这点很有用,举例,允许用户编辑视图,而这个视图可能会被丢弃,而不会影响到另一个视图中显示的数据。
    It has an infrastructure for data store versioning and migration. This lets you easily upgrade an old version of the user’s file to the current version.
    它为数据的存储版本和迁移提供了基础设施。这会让你把用户文件从旧版本升级到新版本变的很方便。
    It allows you to store your data in iCloud and access it from multiple devices.
    For information about how to use Core Data, see Core Data Programming Guide.
    它允许你在iCloud中存储数据并从多个设备访问。关于如何使用Core Data的信息参考Core Data Programming Guide


    Defining a Document-Based Data Model
    定义一个基于文档的数据模型


    A document-based data model is a convenient way to manage the files your app writes to disk. In this type of data model, you use a document object to represent the contents of a single file (or file package) on disk. That document object is responsible for reading and writing the contents of the file and working with your app’s view controllers to present the document’s contents on screen. The traditional use for document objects is to manage files containing user data. For example, an app that creates and manages text files would use a separate document object to manage each text file. However, you can use document objects for private app data that is also backed by a file.
    一个基于文档的数据模型是管理app文件写到磁盘上的方便的方法。这种类型的数据模型,使用一个文档对象来表示磁盘上单个文件的内容(或文件包)。这个文档对象负责读写文件内容,与视图配合工作来在屏幕上显示文档内容。通常使用文档对象来管理包含用户数据的文件。举例,一个创建和管理文本文件的app应该使用独立的文档对象来管理每一个文本文件。但是,你可以为私有app数据使用文本对象,也由一个文件备份。
    Figure 2-2 illustrates the typical relationships between documents, files, and the objects in your app’s data model. With few exceptions, each document is self-contained and does not interact directly with other documents. The document manages a single file (or file package) and creates the in-memory representation of any data found in that file. Because the contents of each file are unique, the data structures associated with each document are also unique.
    图2-2说明了文档,文件和应用程序数据模型对象之间的典型关系。有一点例外的是,每一个文档都是自包含的,不直接与其他文档交互。文档管理一个单独的文件或文件包,并且为在文件中找到的任何数据创建在内存的表达。因为每个文件的内容是独一无二的,每个文档相关的数据结构也是第一无二的。
    图2-2 使用文档来管理文件内容
            Application data model
            Document    Document    Document
                ^           ^           ^
                |           |           |
                V           V           V
               File       File         File
                        File System


    You use the UIDocument class to implement document objects in your iOS app. This class provides the basic infrastructure needed to handle the file management aspects of the document. Other benefits of UIDocument include:
    在iOS app中使用UIDocument类来实现文档对象。这个类提供了处理文件管理的基本功能。UIDocument的其他优点有:
    It provides support for autosaving the document contents at appropriate times.
    它提供了在合适的时间自动保存文档内容
     It handles the required file coordination for documents stored in iCloud. It also provides hooks for resolving version conflicts.
     它处理了在iCloud中存储文档的和要存储的文件的协调工作。它也提供了解决版本冲突的钩子。
     It provides support for undoing actions.
     它提供了undo操作的支持。
     
     You must subclass UIDocument in order to implement the specific behavior required by your app’s documents. For detailed information about how to implement a document-based app using UIDocument, see Document-Based Application Programming Guide for iOS.
     为了实现应用程序的文档所要求的具体的行为你必须子类化UIDocument。关于如何使用UIDocment实现一个基于文档的应用程序,参考"Document-Based Application Programming Guilide for iOS"
    展开全文
  • Model is the abstraction of real world....reveal the essence of objects, help people to locate and resolve problemsData Modelexplicitly determines the structure of data, and defines the operat...

    Model 

    is the abstraction of real world.

    模型是真实世界的抽象。

    reveal the essence of objects, help people to locate and resolve problems

    Data Model

    explicitly determines the structure of data, and defines the operation that can be imposed, in order to represent the characteristic of the world.

    数据模型定义了数据的结构和可执行的操作,以展示出现实世界的特性。

    Data model is the core and fundamental of database

        Data model determines the function and performance of database

    There exists different data models

        From different level, or different point of view

    The evolution of data model promotes the database progress



    Different level of abstraction



    Data models

    Conceptual model:

        documents and organizes the data for communication between functional and technical people

        概念模型用文档和数据用于功能和技术人员的交流。

    Logical model:

        describes data semantics, data relationships, data constraints and data operation in database

        逻辑模型描述了数据库中数据的语义,数据的关系,数据的约束和数据的操作

    Physical model:

        describes how data is orgnized in storage device

        物理模型描述了存储设备上数据的组织方式。

    Steps in Building a DB Application


    概念设计——逻辑设计——物理设计

    ER Model

    is the most popular conceptual model

    ER模型是最流行的一种概念模型

    elements of ER model: 

    Entities, attributes, relationships

    Entities

        real-world objects distinguishable from other objects

        described using a set of attributes

    Entity set

        a collection of similar entities

    实体与实体集的关系如图。


    Attributes

        each has an atomic domain: string, integers, reals, etc.

    For example:


    产品(product)是一个实体集,具体的产品(specific product )是实体。

    price, name, category 是属性。

    Relations

    A mathematical definition:

        if A, B are sets, then a relation R is a subset of A × B. (笛卡儿积)


    Relationship Attribute

    An attribute can also be property of a relationship.

    For instance, the attribute access-date


    ER Relationship Diagrams

    Alternative notation for cardinality Constraints

    下面是一些关于ER图、三元关系的例子:


    三元联系:


    三元关系转化成二元关系:



    展开全文
  • 逻辑模型 - Logical Data Model

    千次阅读 2016-03-09 09:49:41
    承接上一篇博客:Data Model - Conceptual Data Model(概念模型) 逻辑模型(Logical Model)逻辑模型是按照计算机系统的观点来对数据和信息建模,主要用于DBMS的实现。包括: 层次模型 - Hierarchical Model 网状...
  • flowable war包启动失败,报错Caused by: org.flowable.common.engine.api.FlowableException: Error initialising dmn data model 类似问题.比如 Caused by: org.flowable.common.engine.api.FlowableException: ...
  • 报错内容:“The model used to open the store is incompatible with the one used to create ...出现上述异常的原因是 :我们修改了Data Model文件,增加了新的Entity,包括Attribute属性、Relationship关系等等。
  • Core Data 学习: 数据模型(Data Model)

    千次阅读 2016-06-01 15:16:00
    数据模型(Data Model)  前面文章中介绍了Core Data堆栈,它是Core Data的核心部分。并且了解了Core Data堆栈中管理对象上下文(managed object context),持久化存储协调者(persistent store coordinator),管理...
  • EXCEL Data Model 和DAX

    千次阅读 2017-05-21 13:13:28
    最近自学到了一些Excel新技能:之前用excel,做个财务报表、画个图,最多也就弄...而学到了Data Model和DAX之后,这个概念颠覆了。先做一下简单的对比,感受一下SQL和EXCEL的异同之处。 数据操作对比:SQL vs EXC
  • 物理模型 - Physical Data Model

    千次阅读 2016-03-09 11:31:42
    承接上一篇:Database - Logical Data Model(逻辑模型) 物理模型(Physical Model)在Database - Data Model(数据模型) 中已经介绍过,物理模型的具体实现是DBMS的任务,而我们开发人员要做的就是:学习相关DBMS...
  • A logical data model (LDM) helps you analyze the structure of an information system, independent of any specific physical database implementation. An LDM has migrated entity identifiers and is less ...
  • xml data model

    2007-03-23 17:21:00
    xml modelxml data model用于将数据分组,以方便交互。xml data model对于forms global page, 是可选的。通常,model在form的最开头。格式如下: http://www.w3.org/2003/xforms"> // xforms is the namespace
  • 文章目录用MATLAB更改初始data model文件中的参数(1)什么是Data Model文件?Data Model API如何读取data model里面的内容?还有哪些其他实用的API?(从属于prescan.experiment下)用Data Model API修改参数的优势 ...
  • DSF Data Model

    2007-04-10 14:17:00
    DSF Data ModelVersion 1.0Pawel Piech© 2006, Wind River Systems. Release under EPL version 1.0.OverviewThe data model aspect of DSF is only partially complete as compared to the Concurrency and
  • Scorm DataModel实现

    千次阅读 2012-11-26 11:12:31
    SCORM将DataModel中的CMI数据分为八大类,SCORM对每一个数据的定义、用途、所包括的子数据项、输出数据格式、LMS引用数据的行为、SCO使用的样例、支持的API函数、是否必选、数据类型、SCO的访问权限等都做了详细的...
  • Ado.net entity data model 解决:具体:在C:\ProgramData\Package Cache\ 搜索到相应的EFTools.msi .注意:先执行UnInstall(remove),再执行install。 对应版本:VS2012 对应EFTools V11 VS2013 对应EFTools V12...
  • 3.2 内存中的DataModel

    2012-01-11 18:13:17
    3.2 内存中的DataModel 这是个抽象概念,在Mahout中,recommender的输入数据是DataModelDataModel的实现为各种推荐器算法需要的数据提供了有效的使用。例如,一个DataModel可以在输入数据中,提供一个包括所有...
  • 概念模型 - Conceptual Data Model

    千次阅读 2016-03-08 17:11:15
    承接上一篇博客:Database - Data Model(数据模型) 概念模型1. 是现实世界到机器世界的一个中间层次概念模型用于信息世界建模,是现实世界到信息世界的第一层抽象,是数据库设计人员进行数据库设计的有力工具,也...
  • Relational Data Model

    2017-06-03 22:04:16
    The goal of a model is to reduce and abstract the real world into something computable. It is represented as a collection of tables.Relational Model describe how to operate database with som
  • After creating a data model, we will populate it with some sample data we can use for testing. Populating a data model can be done either manually using the hMC, an appropriate cockpi
  • 数据模型指南 Data Model Guideline

    千次阅读 2010-12-26 09:29:00
    Data Model captures the design of the persistent data stores used by the system. This guideline introduces Data Modeling and its use within RUP.  Overview Data Models are used to design the ...
  • Data Model(数据模型)

    2015-04-20 12:04:12
    Data Model(数据模型) Aerospike采用无模式(schema-less)数据模型,这意味着存储在库中的数据不符合严格模式。 这提供了你在Aerospike中存储数据的灵活性-数据修改不需要修改schema,库中已存在的数据也不需要...
  • HBase学习笔记 --- DataModel逻辑图
  • 在使用DataModelSelection时候,一般习惯性的喜欢在xhtml中使用 XXXXBean.Items,这样的话,DataModel不能正常工作,而应该用DataModel在java程序中绑定的名字,如Items。   实例代码如下,请参考。 1. java代码...
  • scorm 2004 datamodel 中文解释

    千次阅读 2013-06-13 16:34:00
    摘录部分: 读写权限指的是RTE对这些参数的读写权限. ...cmi._version (characterstring, RO) Representsthe version of the data model 只读.表明数据模型的版本 cmi.comments_from_learner.
  • 文章目录半结构化数据模型(Semi-structured Data Model)1. 半结构化数据几种数据模型2. 半结构化模型特征3. XML和JSON4. 树状数据结构(Tree Data Structure) (写在前面:由于之前学习过数据库相关知识,这里不再...
  • 【注】由于所评论的链接是英文的,故相应的...link strongly argues against an integration design principle of using some Canonical Data Model, or Common Data Model for business data. I know about this po
  • 很多年前,刚开始接触到 ViewModel 概念的时候,将 DataModel 赋值给 ViewModel 的时候通常会这样做: Id = x.Id, ParentId = x.ParentId, Name = x.Name, Code = x.Code, ...
  • JSF--DataModel

    千次阅读 2010-04-17 23:39:00
    JSF提供javax.faces.model包,数据模型DataModel类位于此包中。DataModel实现了一个抽象任意数据绑定技术,可以被用来适应各种数据源使用JSF组件,为子组件提供Row操作功能(如UIData,表格、列表和树都是它的子类)...
  • self.userstatschartview.datamodel = user_datamodel AttributeError: 'NoneType' object has no attribute 'datamodel' ERROR:superset.app:Failed to create app Traceback (most recent call last): File ...

空空如也

空空如也

1 2 3 4 5 ... 20
收藏数 91,108
精华内容 36,443
关键字:

datamodel