This article addresses the issue of second language writing, with English as a second language, for advanced learners in a UK university. Confirming research findings about the limitations of second language writing, we examine the translation commentaries written by 14 Chinese students on a MA translation programme and find learner problems in generalising from details, developing claims, synthesising concepts, or relating concepts to each other. A translation problem space model is proposed to represent some significant concepts in translation studies from a problem-solving perspective. A further hierarchical network model is proposed based on the problem space model, which helps learners organise their thoughts by properly integrating general and specific concepts. Finally, a CALL programme is designed based on the two models to help students write translation commentaries by calculating keywords in their compositions which represent domain-specific key concepts, and by offering model compositions for comparison. This development protocol is applicable to other domains of ESL writing.