The Object Constraint Language (OCL) is a precise declarative language used to describe rules, constraints, and expressions for Unified Modeling Language (UML) models. Developed initially by IBM, it is now part of the UML standard and managed by the Object Management Group (OMG). OCL allows software architects and developers to specify detailed and unambiguous rules that cannot be easily expressed using UML diagrams alone. Key features of OCL include:

• It is a typed, declarative, and side-effect-free specification language: OCL expressions evaluate to types and query or constrain the system state without changing it.
• It is used to define invariants (conditions that must always hold), pre-conditions (conditions that must be true before an operation), and post-conditions (conditions that must be true after an operation).
• OCL provides a formal way to specify constraints on UML models such as class invariants, operation contracts, initialization, derived attributes, and queries.
• It is used for formal verification and validation of software system requirements, removing ambiguity from specifications and improving software quality.
• OCL can also be used in model-driven engineering tasks such as model transformations and code generation.

In summary, OCL enhances UML by providing a formal textual language to specify detailed constraints and business rules that supplement the graphical UML models, ensuring precision and clarity in system design and development. This makes OCL a valuable tool in software modeling, design, and validation processes. Let me know if you want examples or more details on any specific aspect of OCL.