HL7学习日记3－－第一章的几个问题

jubin

这周跟领导出差了4天，匆匆看完第一章,感觉比较抽象，自己把一些问题和重点笔记罗列了一下，有点散，希望能够抛砖引玉，请大家来谈谈自己的理解。

一、vocabulary是编码概念的抽象集合？
1、vocabulary domain是为下一步字段编码做抽象的概念集合，用于支持class的attribute；
2、字段概念和字段编码完成不同的功能，字段概念仅仅描述字段的含义、值域范围等，字段编码就是字段value；
3、字段概念从HMD通过工具演化出来，字段编码用short concept identifiers产生scheme?
4、vocabulary domain为本地化和使用其他外部编码系统做了抽象层次的准备

For example the Vocabulary domain PhysicalQuantity is associated with both diet_carbohydrate_qty and Diet_energy_qty. The vocabulary domain table may be an HL7-defined table, an HL7-recognized external coding scheme (e.g., LOINC, SNOMED) or some combination of those. It may contain locally-defined codes.

The HL7-defined vocabulary domain tables are stored in the HL7 repository.

二、ITS的作用？
ITS用于解决HL5（会话层）和HL6（表示层）的问题。
HL7 defines its messages at an abstract level（这里说的是从RIM到HMD）. This level emphasizes the semantic content of the messages, not how they are represented, nor how these representations are encoded for transmission.The XML standard defines how to represent XML documents as streams of 8-bit bytes and how opening and closing tags must match. This corresponds to ISO level 5. The XML Document Object Model defines the abstract parse tree of XML documents and corresponds to ISO level 6.

HL7 Version 3 messages can be thought of as the communication of graphs of RIM objects from sender to receiver. The ITS can best deal with representing these messages by having appropriate representations for objects, attributes and Data Types.

三、CMET是什么？
有一些message type定义会refer to CMET
CMETs (Common Message Element Types)express a common, useful and reusable concept。A CMET can be envisioned as a message type fragment that is reusable by other message types.
A CMET is derived from a single D-MIM, defined by the producing committee. Its content is a direct subset of the class clones and attributes defined in that D-MIM, and does not include content from other D-MIMs (It does not “span” D-MIMs).

四、DATA TYPE是什么？
data type就是attribute的结构化形式。有些data type会带很少的内部语义内容，而语义上下文是由相应的attribute本身携带的。一个attribute对应一个data type，一个data type对应0..n个attribute。

五、wapper是什么？
wapper就是message的信封。
HL7 wapper is the envelopes which support the HL7 messages from sender to receiver.Message wrappers are defined in the same way as message content, by defining object classes and related relationships.
The distinction is that wrappers have one or more "stub" classes which define locations within the message which need to be bound to other message structures before the model can be implemented.
Wrappers are defined to provide additional generic information both for message transmission (Transmission Wrapper) and for semantic interpretation (Control Act Wrapper).
HL7 message not only contain the information with some wappers, also carry the commands to coordinate the operation message handling services.

六、为什么需要HMD？
HMD是将classes向XML转化的模版，可以使用RoseTree工具完成。
The communicating systems must be able to determine which of the objects derived from these classes contain the data to be sent. Furthermore, they must be able to navigate to the related objects through the associations that are defined for the classes.
The communicating systems must be aware which of the objects will be sent.
The communicating systems must know the exact sequence in which information will be sent.