UCARConnect can only take in metadata records that are well-formed, in the correct metadata format, and that are valid with respects to the format's schema. In order for an xml record to be well-formed, it must follow the guidelines of the W3 Consortium, such as correct capitalization, inclusion of both start- and end-tags, and proper nesting. A good tutorial for learning the basics of well-formed xml can be found at w3schools.com. Additionally, official documentation about the xml standard can be found at w3.org.
Xml records are valid when they comply with the metadata schema for the format they are written in. For example, all valid lar records must comply with the lar schema. The schema stipulates which fields must be present in lar metadata records, whether they can be used multiple times, whether they have a controlled vocabulary, etc. There are many xml editors which will check for valid and well-formed records.
Besides checking out the sample records, a valid lar xml record will start with the the following declaration and root element <record> (which tells a program where the schema it's following is located):
<?xml version="1.0" encoding="UTF-8"?>
<record xsi:schemaLocation="http://ns.nsdl.org/ncs/lar http://ns.nsdl.org/ncs/lar/1.00/schemas/lar.xsd" xmlns="http://ns.nsdl.org/ncs/lar" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
(...all the required and optional elements such as <identifier>, <subject>, <date>, etc. go here...)
The LAR Best Practices contain detailed instruction for each lar metadata field, however here is a brief Quick-Start guide, overviewing only the required fields. To find definitions of the fields and their vocabulary terms, please see the Best Practices.