Optimization Services









Optimization Services linear Language (OSlL)

Click to see or download the OSlL (or LPFML) XML Schema -> OSlL.xsd (same as lpfml.xsd) [reserved, not to be used]

Click here to go to the legacy LP-FML site.

OSlL (linear) is Optimization Services linear Language to honor the original LP-FML, for first initiative in standardizing linear optimization instances. LP-FML is now officially subsumed in OSiL. Neither OSlL or LPFML is supposed to be used.

Following is a brief description of the initial intention of LPFML:

There are numerous algebraic modeling languages for generating linear programs and numerous solvers for computing solutions to linear programs. This proliferation of modeling languages and solvers is frustrating to modelers who find that only certain languages connect to certain solvers. One way to encourage modeler-solver compatibility is to use a standard representation of a problem instance, so that all modeling languages and all solvers deal with problem instances in the same form. Such a standard should be able to express instance-specific and vendor-specific information, should be simple to manipulate and validate, and should promote the integration of optimization software with other software. Given the increasing importance of XML for data representation and exchange, and XML’s ability to support the characteristics above, it is natural to base a proposal for a standard for representing problem instances on XML. In this paper, we present the LPFML Schema, a W3C Schema for representing linear programming problem instances in XML. We also describe a library of open-source C++ classes that we have written to facilitate the exchange of information between modeling languages and solvers. We show how these classes have been used to provide previously unavailable language-solver connections.


The Optimization Services representation project started with the OSiL for representing general optimization input instances. OSiL has its roots in LPFML for representing linear program instances. For linear programming, an instance can be represented as a list of nonzero coefficients of variables in the objective and constraint functions, along with bounds on the variables and constraint functions. LPFML also has slight support for solver options and optimization outputs. OSiL extends and improves LPFML’s idea for linear program design and adds other optimization types. There is no separate linear instance representation in Optimization Services. We reserve the acronym OSlL (Optimization Services linear Language) in honor of LPFML for providing us the base and insight in linear program representations and for its early adoption of XML technologies in optimization. Optimization Services, however, has its own separate supports for optimization options and results through OSoL (Optimization Services option Language) and OSrL (Optimization Services result Language).


LP-FML is now officially subsumed in OSiL.

Click here to go to the legacy LP-FML site.

Click to see or download the OSlL (or LPFML) XML Schema -> OSlL.xsd (same as lpfml.xsd)