where  S  is  the  similarity  measure  of  current  fixture,  n  is  the  number  of  the
index  feature,    is  the  weight  of  each  feature,    is  the  similarity
measure  of  the  attribute    of  the  i2th  feature  with  the  attribute of  relative
feature of  the  j-th  case  in  the  case  library. At the  same  time,      ,
the value counts as follows: Where   is the value of the index attribute of the i-th feature, and    is the
value of attribute of the relative i-th feature of the j-th case in case library.
So there are two methods to select the analogical fixture. One is to set the value.
If  the  values  of  similarity measure  of  current  cases were  less  than  a  given  value,
those  cases  would  not  be  selected  as  analogical  cases. When  the  case  library  is
initially set up, and there are only a  few cases, the value can be set smaller. If there
are  lots of analogical  cases,  the value  should get  larger. The other  is  just  to  set  the
number of  the analogical  cases  (such as10), which  is  the  largest value of  similarity
measure from the sorted order.
3 Case adaptation and Case Storage
3.1 Case adaptation
     The modification  of  the  analogical  case  in  the  fixture  design  includes  the
following three cases:
1) The substitution of components and the component;
2) Adjusting  the dimension of  components and  the  component while  the  form remains;   
3) The redesign of the model.
If the components and component of the  fixture are common objects, they can
be edited, substituted and deleted with tools, which have been designed.
3.2 Case storage
Before saving a new fixture case in the case library, the designer must consider
whether  the  saving  is  valuable.  If  the  case  does  not  increase  the knowledge  of  the
system,  it  is not necessary  to  store  it  in  the  case  library.  If  it  is valuable,  then  the
designer  must  analyze  it  before  saving  it  to  see  whether  the  case  is  stored  as  a
prototype  case  or  as  reference  case. A  prototype  case  is  a  representation  that  can
describe  the main  features  of  a  case  family. A  case  family  consists  of  those  cases
whose index codes have the same  first 13 digits and different last three digits  in  the
case library. The last three digits of a prototype case are always “000”. A reference
case  belongs  to  the  same  family  as  the prototype  case  and  is  distinguished  by  the
different last three digits.
From the concept that has been explained, the following strategies are adopted:
1) If a new case matches any existing case family, it has the same first 13 digits
as an existing prototype case, so the case is not saved because it is represented well
by  the prototype  case. Or  is  just  saved as a  reference case  (the  last 3 digits are not 事例推理的夹具设计英文文献和中文翻译(4):http://www.youerw.com/fanyi/lunwen_4865.html