The Naxi are a Tibeto-Burman-speaking people that live in China's Yunnan province. Their language is rather closely related to Yi, thus it falls inside the Loloish branch of Tibeto-Burman.
Also, like the Yi Scripts, the Naxi also possess an indigenous "writing system" that records myths, legends, and religious beliefs. However, unlike the Yi, the Naxi system is much more pictographic in nature.
Many call this system "pictograms" for several reasons. One is that the symbols in Naxi is truly pictures of physical objects. But a more important reason is that this system serves more as a mnemonic device, a visual aid for priests retelling myths. The Naxi pictographs do not completely reflect the Naxi language, not even close. The symbols themselves represent the physical objects they resemble. So, the drawing of a tiger really mean a tiger. Symbols that seem to have a less physical shape nevertheless still represent things in the real world. For instance:
Furthermore, many words in a sentence, especially those meaning abstract ideas or concepts, are left out. They have to be supplied from the priest's memory. Sometimes a pictograph can appear only once but read two or three times. And yet some other times a symbol is present to eludicate the meaning of another symbol, but itself is not read.
However, on the other hand, there is a feature in Naxi that does reflect the underlying language. This manifestation is the rebus principle, the use of a symbol associated with a particular word to represent another word homophonous to the first word. For example, the words for "food" and "sleep" are both pronounced "xa3", so the symbol for "food" (which looks like a pot) is also used for "sleep". Only with the knowledge of the Naxi language could the reader decode this relationship.
A writing system must translate into the language it represents. In Naxi the simplest form of language encoding can be found in the use of the rebus principle, and from this I would say that Naxi is less like a full-blown writing system, but resembles more the earliest stages of scripts from around the world.