<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: times new roman,new york,times,serif; font-size: 12pt; color: #000000'><br><br><hr id="zwchr"><br><blockquote id="DWT2853" style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;">It was my intention to have impossible tag. However in that case root_mesh is also impossible, to be parent and will do work. <br></blockquote>Hi Lukasz<br><br>I would recommend to not use root set as a "parent"; I mean, it should not be used as a possible value for a handle tag (which is 0)<br><br>I looked at moab code more carefully, and you can set a handle tag value of 0, it will be written as 0 to the h5m file, and it will be read back as 0 when you load again the file (so your code "works", in the sense that what you saved is read back when you load the file)<br><br>Still, root set (entity handle 0) does not have a corresponding file id in the h5m file. It "works" for you by accident; Internally, we reserve the value 0 for handles that are "not found". 0 is also "not found", so you write 0 and read back 0, because 0 is not "found".<br><br>Root set is always considered to be the set that contains everything in the moab instance; You should not add entities to it (because it already contains everything), and you cannot remove entities from it. It cannot participate in the children-parent set relationships.<br><br>So, you should not use it as a "parent" in your logic. <br><br>You can always create another set that will be a "referenced" parent.<br><br>Best Regards,<br>Iulian<br><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"></blockquote></div></body></html>