* Preparation of writing a gdcmHeader iterator: generalisation of gdcmTagKey

[gdcm.git] / src / gdcmCommon.h

diff --git a/src/gdcmCommon.h b/src/gdcmCommon.h
index e36b21e30046509d25b1d6cbaf7cb2f15dd04b92..08bf07a0904252ba23d3fdf3b2169f5783a5487f 100644 (file)
--- a/src/gdcmCommon.h
+++ b/src/gdcmCommon.h
@@ -3,8 +3,8 @@
   Program:   gdcm
   Module:    $RCSfile: gdcmCommon.h,v $
   Language:  C++
-  Date:      $Date: 2004/09/09 17:49:24 $
-  Version:   $Revision: 1.30 $
+  Date:      $Date: 2004/09/13 12:10:53 $
+  Version:   $Revision: 1.31 $
                                                                                 
   Copyright (c) CREATIS (Centre de Recherche et d'Applications en Traitement de
   l'Image). All rights reserved. See Doc/License.txt or
@@ -96,6 +96,33 @@ const std::string GDCM_BINLOADED = "gdcm::Binary data loaded";
 const std::string GDCM_NOTLOADED = "gdcm::NotLoaded";
 const std::string GDCM_UNREAD    = "gdcm::UnRead";
 
+/// \brief gdcmTagKey is made to old an "universal" (as in URL, Universal
+///        Ressource Locator)  key to a gdcmDocEntry i.e. a dicom tag.
+///        A dicom tag allways has a group and an element, but a set of tags
+///        embeded in various (optionally nested) sequences and sharing
+///        the same group and element all share the same (group, element)
+///        "identifier". Hence the (group, element) cannot be used as an
+///        identifier (in gdcm we shall refer to a "TagKey") of a tag.
+///        In order to construct a proper tag identifier (i.e. a key) we
+///        consider the following definition of a TagKey:
+///        - let Group, Element be the string representation of the
+///          group and element dicom tag members,
+///        - let ItemNumber be the string representation of the integer
+///          index of the considered item number of a sequence,
+///        Let the key of a tag embeded in a sequence, noted SeqTag, be
+///        the form:
+///           /ItemNumber#Group|Element
+///        where "/", "#" and "|" are characters acting as separators.
+///        Then the general form of a gdcmTagKey is given by:
+///           Group|Element<SeqTag>
+///        where <SeqTag> means NO or many instances of SeqTag.
+///        Hence the gdcmTagKey of a tag not "leaving" in a sequence is the
+///        string e.g. 
+///            0028|1201
+///        but the gdcmTagKey of a tag "embeded" is the first item of
+///        a sequence, itself nested in the third item of a sequence is the
+///        string e.g.
+///            0004|1220/2#0008|0082/0#0008|0090
 typedef std::string gdcmTagKey;
 typedef std::string TagName;