## 5 Discussion  
Due to the diverse nomenclatures and LCA development methodologies that are currently available, users face a significant challenge in synthesizing and harmonizing data from different sources within the LCA community. As shown in Table 5 significant differences in nomenclature between sources still exist, as found by [PERSON] et al. [10]. This lack of EF connectivity can lead to flows inadvertently being excluded from an LCIA analysis, which presents significant challenges to LCA developers and can lead to erroneous results. In the past, the only alternative for developers is to spend significant resources to manually map EFs for each individual LCA. With the automated tools in the FEDEFL toolbox, users can greatly decrease the resources necessary to harmonize EFs and improve the accuracy of LCA study results. Users should also be aware of the limitations of mapping files. The mapping files available through the FEDEFL repository are one way mapping files; mappings are completed by FEDEFL to map from other data sources to the FEDEFL. While a flow may be mappable in one direction, it does not mean that the reverse mapping is accurate. In mapping files, flows are mapped using different mapping conditions, \"=\", \"-\", \">\", and \"<\". While some flows are ideal matches and can be matched using the \"=\" signs, this is not always true for all mappings. For example, in one source you may see the flowable name \"Silver(II)\" and in another list they only have \"Silver\". The \"Silver\" flowable is not an exact match to \"Silver(II)\" and can include more silver ions that just \"Silver(II);\" therefore, a \"<\" with the greater side directed at \"Silver\" would be used. This type of mapping is performed at the discretion of the mapping creators and often is performed in instances where the chemical has a known impact. However, not all flows are mapped to proxy flows and users should be careful when using mappings as some flows with known impacts may disappear during the mapping process or end up mapped to flows that the user does not find to be an acceptable proxy flow. The mapping files posted through the FEDEFL were created by developers of the FEDEFL and not necessarily with the collaboration of the original data sources. This creates limitations as flows from the original sources may have been unclear or misinterpreted by the FEDEFL developers due to lack of metadata. Examples of developer-dependent decisions include mapping flows with errors, such as misspelled flows. Often developers are left to either leave misspelled flows out of mappings or map to the flow they believe the original data source was referencing. Mapping developers must make decisions such as whether to map flows with greater specificity to flows with lesser specificity. This can occur for both context information and for flowable information. An example of this challenge is particulate matter. Some databases have flows such as \"Particles (PM2.5)\", \"Particles (PM0.2-PM2.5)\", and \"Particles (PM0.2)\" where the FEDEFL only has \"Particulate matter, \(\leq\)2.5 \(\upmu\)m\". An example where context information may be more specific is the inclusion of some databases of flows with \"long-term\" context subcompartment and the exclusion from the FEDEFL. Decisions such as these create significant challenges for projects such as that undertaken by the GLAD nomenclature working group to provide dual direction mapping files from four LCA developers (i.e., ecoinvent, ILCD, FEDEFL and IDEA), as different developers must spend significant time agreeing on these decisions. The GLAD nomenclature working group has provided a report of the challenges faced during this project in addition to the mapping files so that users may better understand the limitations of mappings. The removal of exchange information from flow names does have an impact on the mapping abilities of FEDEFL flows with other EF lists and ultimately creates challenges with LCA studies.