Eine Leistungsbeschreibung ist eine Beschreibung der Sachleistung bei einem Austauschvertrag, beispielsweise einem Kaufvertrag oder Werkvertrag. Mit der Leistungsbeschreibung wird festgelegt, welche Hauptleistungen der Schuldner der Sachleistung, also im Beispiel der Verkäufer, erbringen muss, d.h. es werden insbesondere die geschuldeten Eigenschaften, Funktionen und Qualitätsmerkmale der Kaufsache beschrieben.

Construction Specifications

According to the American Institute of Architects (AIA) Document A201-2007, the Contract Documents for a construction project consist of “the Agreement, Conditions of the Contract, Drawing, Specifications, Addenda…”, as well as other miscellaneous documents associated with the contract between the project Owner and the Contractor hired to complete the work. Construction specifications, as noted, become a part of the legal documents of the agreement and form a cornerstone of the project design. In fact, in most cases, the construction specifications override the project drawings in the event of conflicting information.

Performance Specifications

A performance specification is a document that specifies the operational requirements of a component or installation. Simply put, a performance specification tells the contractor what the final installed product must be capable of doing.

--------------------------------------------------
Note added at 4 Tage (2015-04-02 06:32:11 GMT)
--------------------------------------------------

Da es sich um juristisch relevante Vertragsbedingungen / vertragliche Anforderungen handelt, beziehe ich mich hier auf das CSI - The Construction Specifications Institute (CSI).
This is an organization that keeps and changes the standardization of construction language as it pertains to building specifications. CSI provides structured guidelines for specification writing in their Project Resource Manual, (formerly called the Manual of Practice (MOP)).