# Law Enforcement Exchange Specification **Entity class:** Law-enforcement data-exchange specification **Domain:** Information sharing / XML / criminal justice **Doc Type:** Standards Node **Maturity:** Developed ## Definition The **Law Enforcement Exchange Specification (LEXS)** is a family of structured message specifications used to package, query, publish, discover, and retrieve law-enforcement information across systems. LEXS was designed to align with national data models including [[wiki/National Information Exchange Model|NIEM]]. ## Query and Publication Roles The ICEPIC research dossier distinguishes search-and-retrieval messages from publish-and-discover exchanges. In the historical LEIS architecture, a partner system could send a standardized query, have the message transformed for the DHS backend, and receive a response without direct knowledge of the source system's proprietary internal format. LEXS is an interoperability mechanism, not a database and not an independent authorization. It specifies how an exchange can be expressed. Agreements, user credentials, access controls, source-system rules, and legal limits determine whether a particular record may be returned or reused. ## Sources / Provenance - [[research/Immigration and Customs Enforcement Pattern Analysis and Information Collection (ICEPIC)|ICEPIC research dossier]] - [DHS — LEIS briefing](https://info.publicintelligence.net/DHS-LEISS.pdf) - [DOJ record for LEXS documentation](https://www.hsdl.org/c/view?docid=487388) ## Relationships - **aligned with:** [[wiki/National Information Exchange Model|National Information Exchange Model]]. - **used by:** [[wiki/DHS Law Enforcement Information Sharing Service|DHS LEIS Service]], [[wiki/OneDOJ|OneDOJ]], and related exchange environments as documented for particular versions. - **transformed through:** [[wiki/IBM DataPower|IBM DataPower]] in the historical LEIS architecture. - **supports:** [[wiki/Semantic Interoperability|Semantic Interoperability]].