> For the complete documentation index, see [llms.txt](https://chembl.gitbook.io/unichem/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://chembl.gitbook.io/unichem/definitions/glossary-of-terms.md).

# Glossary of Terms

**Term:**  Source Data Release\
 **Description:**  (SDR) A data set obtained from a source, constituting all the current assignments in the source. Sometimes simply referred to as a 'Data Release'. Not to be confused with a UDR.\
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**Term:**  src\_release\_number\
 **Description:**  A release number, as defined by the source, for a particular SDR. Each source is defined as having either a 'date' or a 'number' for identifying different SDRs.\
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**Term:**  src\_release\_date\
 **Description:**  A release date, as obtained from the source, for a particular SDR. Each source is defined as having either a 'date' or a 'number' for identifying different SDRs.\
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**Term:**  Release\_U\
 **Description:**  (RU) UniChem-generated integers (One for each source) incremented by 1 for each Data Load from that source. For example, if, for a given source, the CRU is 4 then a total of 4 SDRs have been loaded for this source.\
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**Term:**  Current Release\_U\
**Description:**  (CRU) The current Release\_U for a particular source\
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**Term:**  Data Load\
**Description:**  The process of adding a single 'Source Data Release' into UniChem.\
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**Term:**  UniChem Load Index\
**Description:**  (UC\_LOAD\_INDEX, or ULI) A UniChem-generated integer incremented by 1 for each successful Data Load from any source. The current ULI therefore indicates the total number of separate Data Loads from all sources.\
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**Term:**  UniChem Data Release\
**Description:**  (UDR) Data is loaded into UniChem in a 'production' instance of the database. After several data loads, a copy is made of this database and is made available to users. Each new UDR may therefore contain several additional ULI's compared to the last UDR\
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**Term:**  UniChem Data Release Index\
**Description:**  (UDRI) An integer indicating the number of the UDR. Also called a 'UC\_RELEASE\_NUMBER', or 'UC Rel No.'\
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**Term:**  Query Data Type\
**Description:**  (QDT) The permitted Data Types for querying UniChem. Four such Types exist: src\_id, src\_compound\_id, InChI and InChI Key. As defined [elsewhere](http://howe.ebi.ac.uk:3000/info/srcidExplain)<br>